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 Front Cover
 Florida State Board of Conserv...
 Transmittal letter
 Contents
 Abstract
 Introduction
 Geography
 Geology
 Ground water
 Surface water
 Well exploration
 Quality of water
 Salt-water contamination
 Quantitative studies
 Summary and conclusions
 References
 Figures


FGS






STATE OF FLORIDA

STATE BOARD OF CONSERVATION

DIVISION OF GEOLOGY



FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director



REPORT OF INVESTIGATIONS NO. 27



GROUND-WATER RESOURCES

OF

SEMINOLE COUNTY, FLORIDA


By
Jack T. Barraclough
U. S. Geological Survey


THE BOARD


Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
FLORIDA GEOLOGICAL SURVEY,
OF COUNTY COMMISSIONERS OF SEMINOLE COUNTY
and the
CITY OF SANFORD


TALLAHASSEE
1962










AGIU.
CULTURAL
uBRARy

FLORIDA STATE BOARD

OF

CONSERVATION


FARRIS BRYANT
Governor


TOM ADAMS
Secretary of State



J. EDWIN LARSON
Treasurer



THOMAS D. BAILEY
Superintendent of Public Instruction


RICHARD ERVIN
Attorney General



RAY E. GREEN
Comptroller



DOYLE CONNER
Commissioner of Agriculture


W. RANDOLPH HODGES
Director








LETTER OF TRANSMITTAL









)^/{fdi i ealad'ycad & atvew

Tallahassee
November 1, 1961



Honorable Farris Bryant, Chairman
Florida State Board of Conservation
Tallahassee, Florida
Dear Governor Bryant:
The Division of Geology is pleased to publish, as Florida Geological
Survey Report of Investigations No. 27, a study of the "Ground-Water
Resources of Seminole County, Florida." The study was made by Jack
T. Barraclough, engineer with the U. S. Geological Survey, in coopera-
tion with the Division of Geology, Seminole County commissioners, and
the city of Sanford.
The limestones of the principal artesian aquifer underlie all of
Seminole County and provide the water required for the extensive
farming and industry of the county. This water probably originates in the
recharge area of Polk and Orange counties and from local rainfall. The
report has determined the long-range changes of water levels, provided
seasonal fluctuations and related these to quality-of-water changes.
The study will provide the data required for expansion of pumping,
location of well fields, and treatment of water.

Respectfully yours
Robert O. Vernon, Director
and State Geologist






























Complete manuscript received
July 14, 1961

Published for the Florida Geological Survey by
Rose Printing Company, Inc.
Tallahassee
November 1, 1961










Abstract
Introduction _._
Purpose and scope of investigation
Location and extent of area
Previous investigations
Acknowledgments
Well-numbering system

Geography _'
Topography and drainage
Climate __
Population and development

Geology ___ __
Stratigraphy
Pre-Mesozoic rocks
Eocene series
Lake City limestone
Avon Park limestone
Ocala group
Miocene series
Hawthorn formation
Pliocene or upper Miocene deposits
Pleistocene and Recent deposits
Structure


Ground water
Nonartesian aquifer
Artesian aquifer
Piezometric surface in
Piezometric surface in
Area of artesian flow
Wells
Subirrigation
Water-level records


Florida _
Seminole County


Surface water
Springs
Artesian springs
Water-table springs
Lakes


Well exploration
Electric logs
Resistivity, flow, salinity,


and temperature measurements ___


Quality of water
Color
Specific conductance
Silica
Iron
Calcium
Magnesium
Sodium and potassium
Bicarbonate


CONTENTS


Page
1
2

3
3
5
6


18
19
19
20
22
23
23
S26
_ 28


_~___111~
------------------------ -----------
'---- ____________ -- --

ll-------~-----i-----------------


- ----- ---- -


I-~~--------- ----------- --


------- ----------------------






Sulfate 64
Chloride 64
Fnoride 67
Nitrate 67
Dissolved solids 67
Hardness 68
Hydrogen sulfide 69
Hydrogen-ion concentration 69
Chemical character of ground water 69
Salt-water contamination ___ 71
Quantitative studies _____-------- -- 80
Summary and conclusions 87
References -- 89






ILLUSTRATIONS -
Figure Page
1. Location of Seminole County -__ 4
2. Monthly distribution of rainfall at Sanford 8
3. Geologic units penetrated by water wells in Seminole County 11
4. Configuration and altitude of the top of the Eocene limestones In pocket
5. Configuration and altitude of the top of the Avon Park Limestone In pocket
6. The piezometric surface of the Floridan aquifer __ 21
7. The piezometric surface of the Floridan aquifer in January 1954 In pocket
8. The piezometric surface of the Floridan aquifer in June 1956 In pocket
9. Areas of artesian flow and the height of the piezometric
surface, in feet, referred to land surface in 1954 __ In pocket
10. Location of wells In pocket
11. Relation between the static head and the yield of four flowing artesian
wells in the area around Sanford 25
12. Relation between the static head and the yield of four flowing artesian
wells in the eastern part of Seminole County 27
13. Hydrographs of the daily high water levels in wells 841-121-1 and 847-
113-6 and the monthly rainfall at Sanford 29
14. Hydrographs of wells 841-113-1, 842-117-2, 843-118-2, 844-117-2, 846-
116-11, and the monthly rainfall at Sanford 31
15. Hydrographs of wells 838-113-2, 839-113-1, 840-112-1, 844-115-8, 848-
119-4, and 849-118-5 32
16. Hydrographs of wells 846-123-2 and 847-123-2, about 1% miles ,west of
Paola. __. 34
17. Sweet Water Spring:
a. View of spring and surrounding area 36
b. Closeup view of spring 37
18. Heath Spring, 0.7 mile northwest of Geneva -_38
19. Temperature and chloride content of Heath Spring 39
20. Hydrographs of five lakes in Seminole County 40
21. Lake Geneva showing the low water level on August 13, 1957. 42
22. Hydrographs of wells 839-122-1, 840-120-2, and Lake Orienta 43
23. Electric log, current-meter traverse, and chloride content of water from
well 845-117-10, 3.6 miles south of Sanford _45
24. Electric log, current-meter traverse, and chloride content of water from
well 840-107-2, 2.1 miles north of Chuluota. 47
25. Electric log and chloride content of water from well 848-116-12, 0.5 mile
southwest of Sanford. 48
26. Electric log, current-meter traverse, and chloride content of water from
well 841-110-12, 2.7 miles northeast of Oviedo ___49
27. Electric log and current-meter traverse in well 838-113-3, 2.5 miles south
east of Oviedo. 50


vii






28. Electric log, current-meter traverse, chloride content, temperature, and
yield of water from well 842-111-6, 2.3 miles northeast of Oviedo -- 51
29. Electric log and chloride content of water from well 847-113-31, 3.0
miles southeast of Sanford. ___-- 53
30. Current-meter traverse and chloride content of water from wells 842-
112-2, 2.3 miles northeast of Oviedo, and 842-111-7, 2.3 miles northeast
of Oviedo. 54
31. The dissolved-solids content of water from the Floridan aquifer. In pocket
32. The hardness of water from the Floridan aquifer. In pocket
33. Bar graphs of the chemical analyses of water from 20 artesian wells and
3 springs. 70
34. The relationship of the chemical constituents in ground water to the
distance of the wells from a recharge area centered near Golden and
Silver lakes. 71
335. The relationship of the chloride content of artesian water to the land-
surface altitude __ In pocket
36. The chloride content of water from the upper part of the
Floridan aquifer. In pocket
37. Hydrographs and chloride content of water from wells 844-114-1, 844-
116-1, and 845-113-1. -_ 74
38. Hydrographs and chloride content of water from wells 848-116-2, 848-
117-8, and 849-119-3. ____ 76
39. Hydrographs and chloride content of water from wells 841-110-9 and
841-110-12. ___ 77
40- Hydrographs and chloride content of water from wells 842-112-1 and
846-112-5. _____ 78
41. Data from wells 842-110-2, 843-103-4, 845-113-10, and 848-113-1. __-- 79
42. Data from wells 841-110-1, 841-111-1, and 849-117-1. 81
43. Flow-measuring apparatus 82
44. Semilog plot of recovery versus time in well 841-113-3. _-------- 84
45. Theoretical drawdowns in the vicinity of a well being pumped at a rate
of 1,000 gpm for selected periods of time ___ _---- ---- 86

TABLES
Table Page
1. Geologic units in Seminole County 10
2. Use of inventoried wells _- -----24
3. Diameter of inventoried wells ______-___ 24
4. Chemical analyses of water from wells in Seminole County 57
5. Chloride content of water samples collected at various depths in wells 65
6. Chloride content of water that was collected as wells were being drilled 66
7. Data from recovery tests of artesian wells in Seminole County -- 84






GROUND-WATER RESOURCES OF
SEMINOLE COUNTY, FLORIDA
By
JACK T. BARRACLOUGH

ABSTRACT

Seminole County is in the east-central part of the Florida Peninsula.
The climate is subtropical and the average annual rainfall is more than
50 inches. The area is well suited for the growing of winter vegetables,
even though most of the rain falls during the summer months and the
vegetables must be irrigated.
The surface deposits consist of sand of Pleistocene and Recent Age,
which ranges in thickness from 10 to 75 feet. Beneath this sand are depos-
its of clay and shell beds, which are believed to be of late Miocene or
Pliocene Age. The Hawthorn Formation of middle Miocene Age under-
lies the surface sand where the deposits of clay and shells are absent.
A thick section of limestone of Eocene Age underlies the Hawthorn For-
mation, and, where the Hawthorn is absent, the limestone underlies the
clay and shells of late Miocene or Pliocene Age. The sedimentary rocks
extend to about 6,000 feet below sea level in Seminole County.
The upper part of the limestone section is composed, in descending
order, of the Ocala Group' of late Eocene Age, the Avon Park Limestone
of late middle Eocene Age, and the Lake City Limestone of early mid-
dle Eocene Age.
The section of limestone formations described above and the lower
part of the Hawthorn Formation make up part of the Floridan aquifer,
which is the most important source of ground water in Seminole County.
Water in the Floridan aquifer is under artesian pressure, and wells that
penetrate this aquifer flow at the surface in most of the lowland areas.
The water in the Floridan aquifer in Seminole County is recharged in
Polk, Orange, and Seminole counties.
Fluctuations of artesian pressure in Seminole County result mainly
from differences in rainfall and variations in the rate of withdrawal of
water from wells. In the Oviedo area the seasonal fluctuations of artesian
pressures cause the water level to fluctuate as much as 12 feet. In the
Sanford area, the maximum seasonal fluctuation of water level was about
7 feet. The minimum seasonal fluctuation of water level in the county
was generally between 5 and 6 feet.

'The stratigraphic nomenclature used in this report conforms to the usage of
the Florida Geological Survey.






FLORIDA GEOLOGICAL SURVEY


Comparisons of water-level measurements made during the period
1983-39 with measurements made during the period 1951-56 show that
the average decline of the water level in the Sanford area, in the interval
between those two periods, was about 1 foot. During the same interval,
the average decline of the water level in the Oviedo area was about 3
feet.
The chloride content of water from artesian wells in Seminole County
ranges generally from 5 ppm (parts per million) in the recharge areas
near the towns of Lake Mary, Paola, Longwood, Oviedo, Chuluota, and
Geneva to 7,500 ppm in the area near Mullet Lake. In most of the two
truck farming areas of Sanford and Oviedo, the chloride content of the
water from artesian wells ranges in different areas from about 10 ppm to
slightly more than 1,500 ppm. The minimum observed seasonal variation
of the chloride content of the artesian water in one well near Sanford was
35 ppm and the maximum observed seasonal variation in one well was
265 ppm. The minimum observed seasonal variation of the chloride con-
tent of the artesian water in one well near Oviedo was 16 ppm and the
maximum observed seasonal variation in one well was 180 ppm. Com-
parisons of analyses made in 1933 and 1956 indicate that there has been
little long-term change in the chloride content of the artesian water in
Seminole County.
Chemical analyses show that ground water in parts of Seminole Coun-
tv would be classed as excellent for most uses, and ground water in other
parts of the county would be classed as unusable for almost all purposes.
The artesian aquifer has an average coefficient of transmissibility of
about 185,000 gpd (gallons per day) per foot.

INTRODUCTION
PURPOSE AND SCOPE OF INVESTIGATION
Salt-water encroachment is a problem of great concern to most users
of ground water in Florida. In many coastal areas the lowering of water
levels by heavy pumping contributes to lateral encroachment of salt
water from the ocean. In some inland areas the water-bearing forma-
tions contain salty water at a moderate depth and excessive lowering
of water levels causes upward encroachment of the salty water. Exam-
ples of inland areas with salt-water problems can be found. along most
of the St. Johns River.
An important part of the economy of Seminole County is the growing
and marketing of winter vegetables. The most important farming areas
are in the level lowlands adjacent to Lake Monroe and Lake Jessup,
where adequate supplies of water for irrigation are available from the






REPORT OF INVESTIGATIONS No. 27


natural flow of artesian wells. In parts of the farming areas wells yield
relatively salty water and, locally, the artesian pressure has declined
excessively as a result of heavy withdrawal of water for irrigation and
for vegetable processing. This decline in artesian pressure has resulted
in a decrease in the size of the area of artesian flow and, in some places,
has necessitated the use of pumps on wells that formerly produced an
adequate supply of water by natural flow. The decline of artesian pres-
sure may lead also to contamination of the existing supplies by causing
encroachment of salty water from the formations that underlie the pro-
ducing aquifer.
Recognizing these possibilities, the Board of County Commissioners
of Seminole County requested the U. S. Geological Survey and the Florida
Geological Survey to make an investigation of the ground-water resources
of the county. An investigation was begun in October 1951 by the U. S.
Geological Survey in cooperation with the Florida Geological Survey and
the Board of County Commissioners of Seminole County. The city of
Sanford shared in the cooperation from 1953 through 1955.
The principal purpose of the investigation was to collect and inter-
pret basic information for the safe and efficient development of ground-
water supplies of Seminole County. Special emphasis was placed on the
problems associated with salt-water contamination and declining water
levels.
The field work was begun in 1951 by Ralph C. Health, geologist, under
the direct supervision of H. H. Cooper, Jr., district engineer. The author
was assigned to the project in 1953, under the direct supervision of Mr.
Heath, who was then acting district geologist of the Federal Survey. Dur-
ing the period 1955-58, the investigation was under the direct supervision
of M. I. Rorabaugh, district engineer.

LOCATION AND EXTENT OF AREA
Seminole County comprises an area of about 821 square miles in the
east-central part of the Florida Peninsula (fig. 1). Prior to 1913 the area
in this report was part of Orange County. Sanford, the county seat, is in
the northern part of Seminole County, along the St. Johns River.

PREVIOUS INVESTIGATIONS
The geology and ground-water resources of Seminole County are
described in several reports published by the Florida Geological Survey,
the Florida Academy of Sciences, and the U. S. Geological Survey.
A report by Matson and Sanford (1913, p. 876-881) contains a brief
discussion of the geology and ground-water resources of Orange County,
which at that time included the area that is now Seminole County. A






4 FLORIDA GEOLOGICAL SURVEY


Figure 1. Location of Seminole County.







REPORT OF INVESTIGATIONS No. 27


report by Sellards and Gunter (1913, p. 113) contains information on
wells in Seminole County.
V. T. Stringfield (1984) made a brief investigation of the ground-
water resources of Seminole County as part of a general investigation
of the ground-water resources of the Florida Peninsula. The geology and
ground water of Seminole County are also discussed by Stringfield (1936,
p. 135-136, 162, 174, 188) in a report on the artesian water in the Florida
Peninsula. This report includes a map showing the areas of artesian flow,
a map showing the areas in which the artesian water contains more than
100 ppm of chloride, and the first published map of the piezometric
surface of the principal artesian (Floridan) aquifer. A report on the
geology and artesian-water supply of Seminole County by Stubbs (1937,
p. 24-36) includes two maps of the piezometric surface, a map showing
the areas of artesian flow, and a discussion of the geologic formations
that underlie the county. As a part of his work in the county, Stubbs
periodically measured the water levels in selected wells and analysed
the chloride content of water samples collected from selected wells
(S. A. Stubbs and Irving Feinberg, unpublished records in the files of
H. James Gut, Sanford, Florida).
A report by Unklesbay (1944), describing ground-water conditions
in Orlando and vicinity, includes records of 3 wells and 1 spring in Sem-
inole County. The geology of the State, including formations in Seminole
County, is described in a report by Cooke (1945, p. 225).
A report by Ferguson and others (1947, p. 149-154) contains de-
scriptions of three of the largest springs in the county and chemical
analyses of their waters. Chemical analyses of water from wells in Sem-
inole County are contained in reports by Collins and Howard (1928,
p. 228) and Black and Brown (1951, p. 104).
Heath and Barraclough (1954) prepared an interim report on the
ground-water resources of Seminole County as a part of this investi-
gation.
ACKNOWLEDGMENTS
The author wishes to express appreciation to the many residents of
the county who readily gave information regarding their wells, and to
those who permitted frequent measurements of water levels in their
wells.
Mr. H. James Gut, former mayor and former city commissioner of
Sanford, was chiefly responsible for the initiation of the investigation.
In addition, Mr. Gut thoughtfully saved valuable information collected
by Sidney A. Stubbs in 1937 and furnished these data and other informa-
tion from his files for use during the investigation.







FLORIDA GEOLOGICAL SURVEY


Thanks are extended to others in the county who have been especially
helpful. These men include: Mr. C. S. Lee, Oviedo; Dr. Phillip Westgate,
Central Florida Experiment Station, Sanford; Mr. Benjamin Wiggins, Soil
Conservation Service, Sanford; Mr. Randall Chase, Sanford; and Mr.
LeRoy Hennessey, Longwood. Mr. R. W. Estes (deceased) was also
very helpful.
Appreciation is expressed for the support and cooperation of
many well drilling contractors in the area. Mr. Ernest Hamilton,
Lake Monroe, was especially helpful and cooperative during the
investigation. Other drillers who helped by collecting rock cuttings
included the following: Mr. M. G. Hodges, Paola; Mr. H. C. Long,
Sanford; Mr. F. F. French, Longwood; the Libby and Freeman
Drilling Company, Orlando; and the Layne-Atlantic Company,
Orlando.
Dr. Herman Gunter, former director of the Florida Geological
Survey, and Dr. Robert Vernon, director of the Florida Geological
Survey, furnished much valuable information concerning the geology
of the county.
WELL-NUMBERING SYSTEM
The well-numbering system used in this report is based on latitude
and longitude coordinates. The well number was assigned by
first locating each well on a map that is divided into 1-minute
quadrangles of latitude and longitude, then numbering, consecutively,
each inventoried well in a quadrangle. The well number is a
composite of three numbers separated by hyphens: The first number
is composed of the last digit of the degree and the two digits of
the minute of the meridian of latitude on the south side of a 1-minute
quadrangle; the second number is composed of the last digit of the
degree and the two digits of the minute of the parallel of longitude
on the east side of a 1-minute quadrangle; and the third number
gives the order in which the well was inventoried in the 1-minute
quadrangle. For example, well number 844-114-1 was the first well
inventoried in the 1-minute quadrangle north of 28044' parallel of
latitude and west of the 81014' meridian of longitude. Wells re-
ferred to in the text can be located on figure 10 by this system.
Complete well descriptions, locations, and other data are to be
published as Florida Geological Survey Information Circular No. 34,
and may be obtained for $1.00 per copy.
GEOGRAPHY
TOPOGRAPHY AND DRAINAGE
The topography of Seminole County may be divided into two







REPORT OF INVESTIGATIONS No. 27


types: a flat lowland, characteristic of the area adjacent to Lake
Monroe; and hilly uplands, characteristic of the area in the vicinity
of Lake Mary.
The level lowland includes the area ranging from a few hundred
feet to more than 2 miles wide adjacent to the Wekiva, St. Johns,
and Econlockhatchee rivers and Lake Jessup. The land-surface
altitude within this area ranges from about 5 feet above mean sea
level near the St. Johns River to about 30 feet above sea level where
the lowland area merges into the hilly upland.
The hilly upland includes the remainder of the county. The
surface features of this area include many sandhills and lakes and
some level areas. Many of the lakes probably were formed by the
collapse of the surface sand and clay into caverns formed by the
solution and removal of the underlying limestone by circulating ground
water. The land surface in this area ranges from about 30 feet
above sea level where the area adjoins the level lowlands to about
105 feet above sea level in the vicinity of Altamonte Springs.
The level lowlands and small areas of the hilly uplands are
drained by the St. Johns River and its tributaries, which include
Lake Jessup, the Wekiva River, and the Econlockhatchee River. The
remainder of the hilly uplands drains into closed depressions. Many
of these depressions are probably drained through permeable material
into the underlying limestone aquifers.
CLIMATE
The climate of Seminole County is subtropical. The average annual
precipitation at Sanford for the 49 years of record (1883-87 and
1913-56) is 52.89 inches, according to the records of the U. S.
Weather Bureau. The maximum annual precipitation was 74.06 inches
in 1953, and the minimum annual precipitation was 35.54 inches in
1938. The monthly distribution of rainfall at Sanford and the maximum
and minimum rainfall of record are shown in figure 2. About 70
percent of the precipitation falls during the months of May through
October.
Temperature records at Sanford have been collected by the
weather bureau for 43 years. The mean annual temperature at
Sanford is 72.20F. The lowest mean monthly temperature is 61.40F. in
January; the highest mean monthly temperature is 82.20F. in August.
The average growing season is about 330 days.
POPULATION AND DEVELOPMENT
The 1950 census listed the population of Seminole County as
26,883. Sanford, the largest town and the county seat, had a population






FLORIDA GEOLOGICAL SURVEY


EXPLANATION


16 M
Maximum rainfall
(1913 1956)
14-
Average rainfall
(1913 1956)
12
Minimum rainfall
(1913 1956)


10

8

6

4

2

0


r


7


7
?X


I


/


r


JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC
Figure 2. Monthly distribution of rainfall at Sanford.


-1^-^-


77i~







REPORT OF INVESTIGATIONS NO. 27


of 11,935. The populations of the largest towns were as follows:
Oviedo, 1,601; Altamonte Springs, 858; Longwood, 717; and Lake
Mary, about 800.
Sanford is at the site of Camp Monroe, which was established in
1836 by -troops of the U. S. Army to protect the settlers from the
Seminole Indians. Fort Mellon, a more permanent base named to
honor Captain Charles Mellon, soon replaced Camp Monroe. In 1870,
General Henry S. Sanford purchased 12,535 acres of land west of
Fort Mellon and laid out the town named for him. Sanford was
incorporated in 1877 and included Fort Mellon.
Orange groves were set out in about 1840 and served as a main
source of income. Other crops were grown until the "big freeze" of
1895 blackened most of the agriculture of the State. This freeze caused
the settlers to depend on other crops because it was several years
before the citrus trees would again bear fruit. Shortly after the "big
freeze," a method of subirrigation of crops was developed for use in
the level lowlands. This method of irrigation enabled the area to
maintain an agricultural economy balanced between citrus crops and
winter vegetables According to the Florida State Marketing Bureau's
annual fruit and vegetable report for the 1952-53 season (Scruggs
and Scar rough, 1953), Seminole County had a total of 8,575 acres
under utivation and an additional 7,829 acres planted in citrus groves.

GEOLOGY
STRATIGRAPHY
The only geologic units exposed in Seminole County are deposits
of Pleistocene and Recent Age, which cover the entire county. Infor-
mation about the subsurface geology in the county was obtained from
well cuttings from 69 wells, well logs studied by Sidney A. Stubbs
in the late thirties, and well logs from surrounding counties. Most of
the cuttings from the 69 wells were collected during this investigation
and the remainder were obtained from the files of the Florida
Geological Survey, Tallahassee, Florida.
The geologic formations and .their water-bearing properties are
described in detail in the following pages and described briefly in
table 1. Two cross sections showing the formations penetrated by water
wells are given in figure 3.
PRE-MESOZOIC ROCKS
The top of the pre-Mesozoic rocks in Seminole County is given by
Applin (1951, fig. 2) as about 6,000 feet below sea level. Applin has
classified these crystalline rocks as granite, diorite, and metamorphic











'I14ULIE 1 ~:(.18log Uiifts II 80114fol)U County


Age


Unit


Pleistooene and Recent... .. Undlfferentiated deposits,...



Late Miocene or I'loceno Undifforentiated deposits, ...


Miocene ................. Hawthorn Formation .......


Eocene .................. Ocala Group .............


Eocene ........... ..,.. I Avon Park Limnetono, ......


Eocene . .. .. ... Lake City .... ........


Thicknuie
(feet)


10- 75



0- 83



0-150



0-190





500 -





Over 400


Physical Charactur


Saild, containing some shells and clay..



Sticky blue clay and shell beds., .....


Blue to gray calcareous clay; cream to
gray sandy limestone, containing
grains of cream to black phosphate
rook and fragments of chert,, ,....,,
Cream to tan-gray, soft to hard, gran-
ular, porous foraminiferal marine
limestone ......................



Light-gray to brown, soft to hard, por.
ous to dense, granular to chalky
limestone and dolomitic limestone,,




Hard, brown porous, crystalline dolo-
mite; hard, cream to tan chalky
limestone and dolomitic limestone...


,.,_,,~_..,.,_ ._.,-,,~,~,__. _..._,,,.,_,_.,.~,,,., -.I,


Wator-Iuaring Character

Furnishes water to shallow wells equipped with
screens. Usually adequate for lawn Irrlgation,
domestic and stock use, The water Is softer
and more corrosive than water from the Mlo-
cone and Eocene deposits,
The shell beds yield small to moderate quantities
of water to wells, Water from wells that tap
these beds flow In most of the lower lands. The
clay beds confine water under artesian pressure,
The beds of sandy limestone yield substantial
quantities of water to wells drilled for Irriga-
tlon or domestic uses. The clay beds serve as
an aqulolude.
The second most productive formation in the
county. The Ooala furnishes large quanttites of
water to many wells which tap it only and
contributes considerable water to wells that
tap both overlying or underlying formations
also. It is the first limestone penetrated in most
of the county.
The most productive' formation in Semiinule
County, Yields water to all the deeper wells in
the county and is the only part of the Floridan
aquifer tapped by many wells. Very few wells
draw water from the lower part of the Avon
Park and very substantial additional supplies
could be developed from that part of the for-
mation.
A highly productive formation in the southwest-
ern part of the county but tapped by only a
few wells. No information is available about
the hydraulic properties or the chemical qual-
ity of the water from this formation elsewhere
in the county.



































Figure 3. Geologic units penetrated by water wells in Seminole County.






FLORIDA GEOLOGICAL SURVEY


rocks. They have been termed basement rocks in some publications on
the Florida Peninsula. The depth to the crystalline rocks was deter-
mined from oil test wells in Volusia, Lake, and Osceola counties. The
formations that overlie these crystalline rocks consist of shallow-water
marine deposits, most of which are limestone.
EOCENE SERIES
The upper part of the Eocene Series in Seminole County consist of
the Lake City Limestone, the Avon Park Limestone, and the Ocala
Group (fig. 3, 4).
Figure 4 shows contours in altitude in feet below sea level of the
top of the Eocene limestones in Seminole County. The amount of casing
required to case a well to the uppermost limestone formation can be
determined approximately from this map if the land-surface elevation is
known. The upper surface of the Eocene Limestone ranges from 75 to
about 190 feet below the land surface.
Lake City Limestone
Name: The name Lake City Limestone was given by Applin and
Applin (1944, p. 1680) to a limestone of Claiborne (middle Eocene)
Age penetrated in a well at Lake City, Florida.
Lithology: The Lake City Limestone consists of alternating layers of
hard, brown, porous crystalline dolomite and hard, cream to tan chalky
limestone and dolomitic limestone.
Distribution and thickness: Cooke (1945, p. 45-46) states that the
Lake City Limestone underlies all of Florida except the northwestern
part, where the limestone grades laterally into a plastic facies related
to the Cook Mountain Formation of Claiborne Age.
According to Applin and Applin (1944), the Lake City Limestone
ranges in thickness from 400 to 500 feet in the northern part of Florida
and from 200 to 250 feet in the southern part. The Lake City is more
than 400 feet thick in the southwestern part of Seminole County.
Stratigraphic relations: In most of the Florida Peninsula, the Lake
City Limestone unconformably overlies the Oldsmar Limestone. In Sem-
inole County, the Lake City is overlain by the Avon Park Limestone. In
the southwestern part of Seminole County, the top of the Lake City Lime-
stone was penetrated about 600 feet below sea level in well 839-125-2
(fig. 3).
Water-bearing characteristics: The Lake City Limestone is the oldest
formation penetrated by water wells in Seminole County. Only a few wells
have been drilled into this formation because adequate supplies of water
can generally be obtained from the overlying deposits, although the Lake






REPORT OF INVESTIGATIONS No. 27


City Limestone appears to be highly productive in Seminole County.
The largest yield pumped from a well in Seminole County was reported
to be 8,100 gpm (gallons per minute) and this was obtained from a well
that penetrates more than 400 feet of Lake City Limestone and less than
200 feet of Avon Park Limestone.
Water from the Lake City is somewhat less mineralized than water
from the overlying formations in the southwestern part of Seminole
County and northern Orange County. This is probably not true where
the overlying formations contain salt water. The good quality of the
water from the Lake City Limestone may be due to the fact that the
formation contains a considerable percentage of dolomite or dolomitic
limestone which is less soluble in water than is limestone. No informa-
tion is available concerning the chemical quality of the water in this
formation in any area where the overlying formations contain salty
water.
The Lake City Limestone could become an important aquifer in some
areas of Seminole County if large quantities of ground water are required.
In order to fully appraise the Lake City Limestone as an aquifer, it
would be necessary to drill several wells into the formation in different
parts of the county. The hydraulic properties of the formation and the
chemical quality of the water could then be determined.
Avon Park Limestone
Name: The name Avon Park Limestone was given by Applin and
Applin (1944, p. 1680) to a limestone of Claiborne (middle Eocene) Age
penetrated in a well at the Avon Park Bombing Range in Polk County,
Florida.
Lithology: The Avon Park Limestone consists of layers of light gray
to brown, soft to hard, porous to dense, granular to chalky limestone.
The formation has been irregularly dolomitized since deposition, but the
original structures of the rock generally have been preserved.
Distribution and thickness: The Avon Park Limestone underlies most
of the Florida Peninsula. It is exposed in parts of Citrus and Levy counties
and is the oldest formation that crops out in Florida.
According to Applin and Applin (1944), the thickness of the Avon
Park Limestone ranges from 50 feet or less in northeast Florida to 650
feet in the southern part of the Florida Peninsula. In the southwestern part
of Seminole County, the Avon Park Limestone is more than 500 feet thick.
Stratigraphic relations: The Avon Park Limestone rests -conformably
upon the Lake City Limestone. In Seminole County, the Avon Park is
unconformably overlain by the Ocala Group except where the Ocala is






FLORIDA GEOLOGICAL SURVEY


absent in the north-central part of the county. Here the Avon Park is
overlain by the Hawthorn Formation or younger deposits.
Structure: Subsurface contours on the top of the Avon Park Limestone
are shown in figure 5. This figure shows the top of the Avon Park Lime-
stone to be 27 to about 100 feet below sea level in the area around
Sanford and about 250 feet below sea level in the southeastern part of
the county. The eroded surface of the Avon Park Limestone slopes south-
southeast about 25 feet per mile in the area from Lake Jessup south and
southeast toward Orange County. West of Sanford the surface of the Avon
Park slopes west, toward the Wekiva River, about 20 feet to the mile.
Water-bearing characteristics: The Avon Park Limestone yields more
ground water in Seminole County than any other formation. This is due
principally to its wide areal extent, thickness, and high permeability.
The Avon Park is the shallowest limestone formation that underlies all
of Seminole County, and supplies water to most of the deeper wells. The
large amount of water obtained from this limestone demonstrates its high
permeability. Well 840-107-2 2.1 miles north of Chuluota, flows about
350 gpm from the Avon Park (fig. 24).
Most of the existing wells penetrate only the upper part of the Avon
Park Limestone; however, the lower part of the formation could become
important if even larger quantities of water are needed.

Ocala Group
Name: The Ocala Limestone was named for limestone outcrops near
Ocala, Marion County, by Dall and Harris (1892, p. 103), who believed
that it was Eocene or Oligocene in age. Cooke (1926, p. 251-297) con-
cluded that the limestone was of Jackson Age (late Eocene). Cooke and
Mossom (1929, p. 47-48) defined the name Ocala as including all rocks
of Eocene Age exposed in Florida. Applin and Applin (1944, p. 1683-
1684) stated that it was possible to separate the Ocala Limestone into
an upper and lower member, and listed some characteristic Foraminifera.
On the basis of differences in lithology and fossil content of the Ocala
Limestone, Vernon (1951, p. 156-171) restricted the name Ocala Lime-
stone to the upper part and named the lower part the Moodys Branch
Formation. He further subdivided the Moodys Branch Formation into the
Williston Member at the top and the Inglis Member at the bottom.
Recently, Puri (1953, p. 130) changed the name of the Ocala Limestone
(restricted) to Crystal River Formation and raised the Williston and
Inghs members of the Moodys Branch to the rank of formations. These
three formations, the Crystal River, Williston, and Inglis, are now collec-
tively referred to as the Ocala Group by the Florida Geological Survey.






REPORT OF INVESTIGATIONS NO. 27


Lithology: The Ocala Group consists of white-cream to tan-gray soft
to hard, granular, porous foraminiferal marine limestones. In most places
the Crystal River Formation is white to cream and parts of it are com-
posed almost entirely of remains of large foraminifers. The Williston and
Inglis Formations generally are harder, more granular and contain fewer
large Foraminifera than the overlying Crystal River.
Distribution and thickness: The Ocala Group underlies most of Flor-
ida except the east-central part of the peninsula (Applin and Applin,
1944, p. 1685). It is thin or missing in the northern part and in a small
area in the southwestern part of Seminole County. The thickness of the
Ocala Group ranges generally from 0 to 190 feet. Vernon (1951, p. 57)
states that the Ocala Group has been thinned by erosion along the flanks
of a structural high near Sanford and removed from the crest of the
high. The Sanford high is described by Vernon (1951, p. 57) as the up-
thrown side of a closed fold that has been faulted.
Stratigraphic relations: The Ocala Group lies unconformably on the
Avon Park Limestone in the Florida Peninsula, and is overlain uncon-
formably by the Hawthorn Formation. In places in the northern part of
the county where the Ocala Group is present and the Hawthorn is absent,
the Ocala is overlain unconformably by deposits of Pliocene or late
Miocene Age.
Structure: The altitude of the top of the Ocala Group ranges from
near sea level near the town of Lake Mary to about 113 feet below sea
level near the village of Lake Monroe.
Water-bearing characteristics: The Ocala Group is a very productive
part of the Floridan aquifer and next to the Avon Park Limestone is the
most productive source of ground water in Seminole County. Hundreds
of wells in the county tap only the Ocala Group. Wells penetrating the
Ocala yield from a few gallons per minute to more than 500 gpm. Figure
27 shows that well 838-113-3, 2.5 miles southeast of Oviedo, flows 170
gpm from the Ocala. The Ocala yields about 200 gpm to well 842-111-6,
2.3 miles northeast of Oviedo, as illustrated in figure 28.
MIOCENE SERIES
Hawthorn Formation
Name: The name Hawthorn Formation was first applied by Dall and
Harris (1892, p. 107) to rocks of early and middle Miocene Age that are
exposed near Hawthorn in Alachua County, Florida.
Lithology: The Hawthorn Formation in Seminole County consists of
beds of blue to gray, calcareous clay, alternating with beds of cream
to gray sandy limestone containing numerous grains of black to cream
phosphate rock and fragments of chert.






FLORIDA GEOLOGICAL SURVEY


Distribution and thickness: The Hawthorn Formation apparently un-
derlies the entire Florida Peninsula except in parts of the Ocala uplift
and the Sanford high, where it has been eroded. It is present throughout
Seminole County except in the northern part, along the St. Johns River,
where it has been removed by erosion.
According to Bishop (1956, p. 27), the Hawthorn Formation has a
maximum thickness of 650 feet in Highlands County, Florida. Cooke
(1945, p. 145) states that the Hawthorn is about 400 feet thick in Nas-
sau County, Florida. In Seminole County, the maximum observed thick-
ness of the Hawthorn Formation was 150 feet in a well at the south-
western part of the county.
Stratigraphic relations: The Hawthorn Formation unconformably
overlies the Ocala Group in most places. Where the Ocala is absent, the
Hawthorn rests unconformly upon the Avon Park Limestone. The Haw-
thorn Formation is unconformably overlain by deposits of Pliocene or
late Miocene Age or by deposits of Pleistocene Age. The study of well
cuttings in Seminole County has not revealed any rocks representing the
time interval between the Ocala Group and the Hawthorn Formation.
Water-bearing characteristics: The beds of sandy limestone in the
Hawthorn Formation yield substantial quantities of water to some wells
and are an important source of water for domestic and irrigation supplies.
Well 842-111-6, 2.3 miles northeast of Oviedo (fig. 28), obtains at least
500 gpm of water from the Hawthorn Formation. However, the Haw-
thorn Formation includes clay beds of low permeability, which confine
the water in the underlying limestones.
PLIOCENE OR UPPER MIOCENE DEPOSITS
Name: The beds of Pliocene Age exposed along the Caloosahatchee
River in the vicinity of La Belle, Hendry County, Florida, were first
recognized by Heilprin (1887). Dall (1887) described them as the
Caloosahatchie beds. Matson and Clapp (1909) used the term Caloosa-
hatchee marl for the deposits of Pliocene Age in the vicinity of the
Caloosahatchee River but proposed the term Nashua Marl for the depos-
its of Pliocene Age they found in the valley of the St. Johns River. Cooke
and Mossom (1929, p. 152) included the Nashua in the Caloosahatchee
Marl.
Vernon (1951, fig. 13, 33) considered the Caloosahatchee Marl to
be of late Miocene Age. As the correct age of these deposits has not been
determined, they are referred to in this report as Pliocene or upper
Miocene deposits.
Lithology: The Pliocene or upper Miocene deposits consist of sticky
blue clay and shell beds.






REPORT OF INVESTIGATIONS No. 27


Distribution and thickness: The deposits of Pliocene or late Miocene
Age are found in wells in the northern part of Seminole County, especially
along the St. Johns River valley, but do not crop out in Seminole County.
Stubbs (1987, p. 30) gives the maximum measured thickness of the
Pliocene or upper Miocene deposits as about 70 feet in the St. Johns River
valley, although he states that they may be thicker. Information from
well cuttings examined during the present study shows the maximum
thickness of these beds to be 83 feet.
Stratigraphic relations: The Pliocene or upper Miocene deposits lie
unconformably upon the Hawthorn Formation where it is present, and
upon the limestones of Eocene Age where the Hawthorn is absent. The
Pliocene or upper Miocene deposits are overlain unconformably by
deposits of Pleistocene Age.
Water-bearing characteristics: The shell beds yield small to moderate
quantities of water to wells. Of the wells .that penetrate the shell beds,
some draw entirely from them, but most also are open to the underlying
limestone and obtain water from both sources.
PLEISTOCENE AND RECENT DEPOSITS
Lithology: The Pleistocene and Recent deposits in Seminole County
consist of clear to frosted, fine to coarse quartz sand. In areas near the
St. Johns River, the deposits also include some shells and thin beds of
clay. Beneath the level lowlands of Seminole County, thin layers of hard-
pan have been formed at a depth of 3 to 5 feet through cementation
of sand by iron oxide.
Distribution and thickness: The Pleistocene and Recent deposits
mantle the entire county. They range in thickness from 10 to 75 feet.
Stratigraphic relations: In Seminole County, the Pleistocene and Re-
cent deposits rest unconformably upon deposits of Pliocene or late Mio-
cene Age, and upon the Hawthorn Formation where the beds of Pliocene
or late Miocene Age are absent.
Water-bearing characteristics: The Pleistocene and Recent deposits
furnish water to shallow driven wells that are equipped with screens.
The deposits will yield sufficient quantities of water to most wells for
domestic use and lawn irrigation. Most of the wells screened in these
deposits yield soft water that is more acid than water from the limestone
formations. The water from many of the wells contains objectionable
amounts of iron.
STRUCTURE
The contours in figure 4 show the configuration of the surface of
the limestones of Eocene Age. The contours represent the surface of






FLORIDA GEOLOGICAL SURVEY


ihe Avon Park Limestone in the Sanford area and in an area south of
AItamonte Springs where post-Eocene erosion removed all the
Ocala Group. In the remainder of Seminole County, the contours
represent the surface of the Ocala Group. This surface (fig. 4) has
many irregularities because it has been eroded and because many
sinkholes exist in the area. Some geologic evidence suggests that several
of the irregularities actually may be faults.
Geologic data in Seminole and Volusia counties (Wyrick, 1960)
suggest the presence of a downthrown fault block along the north edge
of Seminole County and south edge of Volusia County. This fault
block underlies part of the St. Johns River valley and most of Lake
Monroe. A surface expression of this fault block is probably shown by
the westerly offset of the St. Johns River along the northern part of
the county. The upper part of the St. Johns River generally flows
north-northwest until it reaches the northeast corner of Seminole
County. The river turns at that point and flows in a westerly direction
for about 18 miles. Then the river turns and continues in the original
northerly direction.

GROUND WATER
Ground water is the subsurface water in the zone of saturation,
the zone in which all pore spaces are filled with water under
pressure greater than atmospheric. Ground water is derived almost
entirely from precipitation. Part of the precipitation returns to the
atmosphere by evaporation and the transpiration of plants and part
drains from the land surface into lakes and streams; the remainder seeps
into the soil zone where some is retained and some continues downward
to the zone of saturation to become ground water. Ground water moves
laterally, under the influence of gravity, toward places of discharge such
as wells, springs, surface streams, lakes, or the ocean.
Ground water may occur under either nonartesian or artesian
conditions. Where it is not confined its upper surface, the water table,
is free to rise and fall and it is said to be under nonartesian or
water-table conditions. Where the water is confined in a permeable
bed that is overlain by a less permeable bed, so that its upper sur-
face is not free to rise and fall, it is said to be under artesian conditions.
The term "artesian" is applied to ground water that is confined
under sufficient pressure to rise in wells above the top of the
permeable bed that contains it, though not necessarily to or above
the land surface. The height to which water will rise in an artesian
well is called the artesian pressure head. The piezometric surface is
an imaginary surface to which water from an artesian aquifer will






REPORT OF INVESTIGATIONS No. 27


rise in tightly cased wells that penetrate the aquifer. Where the
piezometric surface is above the land surface, artesian wells will
flow under natural pressure.
An aquifer is a formation, group of formations, or part of a
formation-in the zone of saturation-that is permeable enough to
transmit usable quantities of water to wells. Areas in which water
enters the aquifers are called recharge areas and areas in which
water is lost from aquifers are called discharge areas.

NONARTESIAN AQUIFER
Ground water ir Seminole County occurs under either non-
artesian or artesian conditions. The water in the surficial sands of
Pleistocene and Recent Age is under nonartesian conditions in all
parts of the county except a few small areas where the sands are
overlain by thick beds of peat or clay.
Wells drawing water from these sands are used mainly for domestic
supplies, although many of these wells are used for lawn and garden
irrigation. Generally, these wells are equipped with hand pumps,
but many of the hand pumps are being replaced with electric pumps.
Probably not more than 400 wells draw water from the sands of
Pleistocene and Recent Age in Seminole County.
The nonartesian aquifer is replenished by local precipitation. In
addition to this recharge, some of the water discharged from the
aquifer by pumping is returned to the aquifer by downward infiltration
of irrigation water. Water is lost from the aquifer by natural discharge
through springs into lakes and streams, by downward percolation into
the artesian aquifer in areas where the piezometric surface is below
the water table, and by withdrawal from wells. Water from the
aquifer generally contains about 50 ppm of dissolved solids in those
areas where the water in the aquifer has not been contaminated by
highly mineralized artesian water. In many areas of the county, water
from the nonartesian aquifer contains an excessive amount of iron,
which can stain clothes, fixtures, and utensils.

ARTESIAN AQUIFER
The principal sources of water in Seminole County are deposits
that form a part of the principal artesian aquifer of the Florida
Peninsula and adjacent area. This aquifer in Seminole County is
composed of beds of sand and shell in the lower part of the deposits
of Pliocene and late Miocene Age, the permeable parts of the Hawthorn
Formation, and limestone formations of middle and late Eocene Age.






FLORIDA GEOLOGICAL SURVEY


Stringfield (1936) first described the principal artesian aquifer
in Florida. The name Floridan aquifer, which will be used in this
report, was proposed by Parker (Parker, et al., 1955, p. 188-189) to
include "parts or all of the middle Eocene (Avon Park and Lake
City limestones), upper Eocene (Ocala Limestone), Oligocene
(Suwannee Limestone), and Miocene (Tampa Limestone, and per-
meable parts of the Hawthorn Formation that are in hydrologic
contact with the rest of the aquifer)." The artesian water is confined
by relatively impermeable layers in the limestones and by the
overlying clay of Miocene Age which extends over most of the State.
Differences in static head, chloride content, and temperatures of water
at different depths in some parts of Seminole County suggest that
relatively impermeable beds may be continuous over large areas,
and that the Eocene limestones consist of several relatively thin
aquifers rather than one thick aquifer.
The height to which water will rise in an artesian well is called
the artesian pressure head. The head at any place in the artesian
aquifer is controlled in part by the head in the recharge area, which
in turn is determined by the amount of replenishment that reaches
the aquifer from rainfall. Periodic measurements of the pressure head
and the water levels in wells are an important part of a ground-water
investigation. Stringfield (1936, p. 195) made a series of water-level
measurements in selected wells in Seminole County. In 1937, Stubbs
resumed measurements in several of the wells measured by Stringfield.
and also began measurements in other selected wells (S. A. Stubbs
and Irving Feinberg, unpublished records in the files of H. James Gut,
Sanford, Florida). Stubbs (1937, p. 33) stated that the minimum
permanent loss of head within the flowing-well area ranged from 4
to 10 feet during the period 1912-37. During the current investigation
measurements were resumed in many of the wells measured by
Stringfield and Stubbs, to determine if there had been any progressive
decline of artesian head. In addition, periodic measurements were
made in 40 other wells to determine the seasonal fluctuations of the
water level in different parts of the county.
PIEZOMETRIC SURFACE IN FLORIDA
The piezometric surface of the Floridan aquifer in Florida is
shown by the contour lines in figure 6. The first map of the piezometric
surface of the principal artesian aquifer in Florida was compiled
by Stringfield (1936, pi. 12). The contours on the piezometric surface
indicate the direction of movement of the artesian water. Water enters
the aquifer in the areas in which the piezometric surface is high and









REPORT OF INVESTIGATIONS No. 27


"posMM scott
II o,_ a so ., 11, .. b. IF
..I .. ... I ..... ...." I

Figure 6. The piezometric surface of the Floridan aquifer, 1949.
moves in a direction approximately perpendicular to the contour lines
toward the areas in which the piezometric surface is low. One of the
most notable features of the piezometric surface in Florida is the dome
centered in Polk County, which indicates that considerable recharge
enters the Floridan aquifer in Polk County and some surrounding
counties.
In Polk County, the western part of Orange County, and some
parts of Seminole County, water enters the Floridan aquifer through
numerous sinkholes that penetrate the Hawthorn and younger for-
mations. The contours on figure 6 show that the artesian water flows
northeast from the recharge area centered in Polk County toward
Seminole County and the adjacent area. This map shows the principal
recharge areas for the Floridan aquifer, but the map is not detailed
enough to show the many small recharge areas that are known to
exist.






FLORIDA GEOLOGICAL SURVEY


PIEZOMETRIC SURFACE IN SEMINOLE COUNTY
The first published maps of the piezometric surface in Seminole
County (Stubbs, 1937, p. 25-26) show in considerable detail the
direction of ground-water flow in the county. Maps of the piezometric
surface drawn during the current investigation generally agree with
those drawn by Stubbs. One difference occurs in the area northeast of
Oviedo where Stubbs' map shows a recharge area in an area of
flowing wells. This discrepancy is believed to be due to an error in
leveling by Stubbs or to using an incorrect benchmark elevation.
Figure 7 shows the piezometric surface of the Floridan aquifer
in Seminole County during near record-high water levels in January
1954. The annual rainfall at Sanford in 1953 was 74.06 inches, which
is the highest on record. Most of this rain, or 51.60 inches, fell during
the period July 1 to December 31, 1953. The maximum artesian
pressure measured in January 1954 was 66 feet above sea level in a
well 6 miles southwest of Oviedo and the minimum pressure measured
was 11 feet above sea level in a well 6 miles north of Geneva in the
St. Johns River valley.
The piezometric map shows that in general the flow of water in
the county is toward the northeast. The effect of ground-water dis-
charge near Sanlando Springs, and in areas 2 miles south of Lake
Mary and 2 miles northeast of Oviedo is shown by depressions in the
piezometric surface (fig. 7). The effect of ground-water recharge in
the areas near Geneva, south of Oviedo, near Chuluota, south of
Sanford, and south of Paola is shown by mounds in the piezometric
surface (fig. 7). The contours also indicate discharge into the St.
Johns and Wekiva rivers and into the southwest part of Lake Jessup.
Figure 8 shows the piezometric surface of the Floridan aquifer at
near record-low conditions in June 1956. The total rainfall at Sanford
was only 16.45 inches for the 8-month period from October 1, 1955
to May 31, 1956. The difference in artesian pressure from the high
level shown on figure 7 to the low level shown on figure 8 is
generally about 5 feet, although one well showed a decline of 10 feet.
Figure 8 shows a piezometric high near Golden and Silver lakes,
:3J miles south of Sanford, which indicates that this is a recharge area.
The highest water level measured in Seminole County during June
1956 was 53 feet above sea level in two wells located near Altamonte
Springs. The lowest water level measured during this dry period was
7 feet above sea level in a well located 6 miles north of Geneva in the
St. Johns River valley. As figures 7 and 8 show approximately
the maximum and minimum conditions, respectively, the piezometric
surface would usually be somewhere between these two extremes.






REPORT OF INVESTIGATIONS No. 27


AREA OF ARTESIAN FLOW
Whenever the piezometric surface stands higher than the land
surface, artesian wells will flow. The approximate areas of artesian
flow in 1954 in Seminole County are shown in figure 9. The principal
area of flow extends in an unbroken band along the Wekiva River
to the St. Johns River and continues along the St. Johns River to
a point about 4 miles east of Lake Jessup. The band includes
both sides of Lake Jessup and the farming area southwest of Oviedo.
East of Oviedo the area of flow extends down the valley of the
Econlockhatchee River to the St. Johns River.
The area of artesian flow was probably larger prior to the agricul-
tural development of the county. In fact, in parts of the farming
area in the vicinity of Sanford, the boundary was probably more than
half a mile farther south than it was in 1956. In most of the farming
areas the boundary of the area of flow has receded onto the level
lowlands, where a decline in artesian pressure of 1 foot results in a
decrease of several hundred feet in the width of the area of flow.
Figure 9 shows also contours which represent the height, in feet,
referred to land surface, to which water will rise in artesian wells
penetrating the limestone aquifer. It shows that the maximum depth
to water is more than 50 feet below land surface in an area near
the southwest corner of the county and at Geneva. The artesian pres-
sure head is more than 20 feet above the land surface in an area
adjacent to the Little Wekiva River, the east edge of Lake Monroe,
and around most of Lake Jessup. Along Howell Creek, at the south
side of Lake Jessup, water from tightly cased wells drilled into the
limestone aquifer will rise more than 30 feet above the land surface.

WELLS
One important phase of any ground-water investigation is the
well inventory, or collection of data on wells. Figure 10 shows the
location and distribution of 874 wells, which were inventoried during
the investigation, and which represent 18 percent of the total number
of wells in the county. Of this number, 50 wells draw water from
the nonartesian aquifer and 824 wells, of which 424 flow, draw
water from the Floridan aquifer. The following table shows a division
of the wells according to their use.
The relative percentage of the wells of each diameter would probably
remain about the same if all the wells in the county were inventoried.
Table 3 shows that almost 47 percent of the inventoried wells are 2
inches in diameter.







FLORIDA GEOLOGICAL SURVEY


TABLE 2. Use of Inventoried Wells
Use of well Number
Domestic 322
Irrigation 312
Unused 137
Industrial and Public Supply 62
Stock 39
Other uses 2
Total 874
The following table shows a classification of the wells according to
their diameter.
TABLE 3. Diameter of Inventoried Wells.
Well diameter Number of Percent of
(inches) wells total
1Y 49 5.6
2 407 46.6
2Js 28 3.2
3 173 19.8
4 123 14.1
5 9 1.0
6 47 5.4
8 21 2.4
over 8 17 1.9
Total 874 100.0
Artesian wells in the county range in depth from 33 to 1,122 feet
but more than 90 percent of them are between 75 and 250 feet deep.
More than 4,500 wells are believed to draw water from the artesian
aquifer in Seminole County.
The relation between the height of the static head above the well
outlet and the yield of four wells in the Sanford farming area is shown
in figure 11. The measurements of yield in gallons per minute and'arte-
sian pressure in feet above sea level are shown as solid dots. Each graph
is drawn as a wedge to cover the variations in the accuracy of the meas-
urements.
The yield of a flowing well depends primarily upon the water-
transmitting capacity of the formations penetrated by the well, the friction
losses within the well, the thickness of aquifer penetrated by the well,
and the height of the static head. The yield of different wells may be
compared by using the specific capacity, which is the yield in gallons
per minute per foot of drawdown. In flowing wells, the drawdown is
approximately equal to the height of the static head above the well out-
let Therefore, the approximate specific capacity of these wells may be
determined by dividing the yield of the wells in gallons per minute by
the static head in feet.






REPORT OF INVESTIGATIONS No. 27


Well 1849-117-1 **
iri.diameter






18

17

16-

15
16 -- ///- -- -




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13

12
//
II

10
Elevation of discharge ipe
9 I
0 5 10 15 20 2!

25 1 I
Well 847-113-21
3ir diameter reduced
t24 _iO meter /

23

levation of discharge pipe
oo I-I


YIELD IN GALLONS


25I
Well 848-113-1
2in. diameter.
24


23
22

21

20

19
Elevation of di charge pipe

180 5 10 15 20 2


PER MINUTE


Figure 11. Relation between the static head and the yield of four flowing artesian
wells in the area around Sanford.


20 25


1


'-0 5 10 15






FLORIDA GEOLOGICAL SURVEY


The specific capacity of well 849-117-1 was only 1.7 gpm per
foot of drawdown and the yield of the well ranged from 14 to 21 gpm as
the artesian pressure increased 3.5 feet. Well 848-113-1 had a specific
capacity of 2.5 gpm per foot of drawdown and the yield of the well
ranged from 4.5 to 12.5 gpm as the artesian pressure increased 4 feet.
Well 845-113-10 had a specific capacity of 6.6 gpm per foot of drawdown
and the yield of the well ranged from 0.5 to 22 gpm as the artesian
pressure increased 3 feet. Well 847-113-21, which is a 3-inch well reduced
to a 2-inch outlet, had a specific capacity of 11.1 gpm per foot of draw-
down and the yield ranged from 0 to 20 gpm as the artesian pressure
increased 1.8 feet. The average specific capacity for the 2-inch wells for
which data were available is 3.9 gpm per foot of drawdown.
Figure 12 is similar to figure 11 as it shows data on the specific capa-
city of three wells, 2 inches in diameter, which are located northeast of
Oviedo and one well, 3 inches in diameter, which is located south of Lake
Harney. The three wells northeast of Oviedo had specific capacities of
5.5, 7.2, and 10.1 gpm per foot of drawdown. The average specific
capacity of the 2-inch wells was 7.6 gpm per foot of drawdown. The
3-inch well, south of Lake Harney, had a specific capacity of 15.8
gptm per foot of drawdown, and the yield rose from 7 to 65 gpm as
the artesian pressure increased 3.1 feet.
The measurements of the yield of these selected wells show that
the wells in the Oviedo area have a higher specific capacity than the
wells in the Sanford area. The graphs show also the reduction in the
vield of a well with each foot reduction in the static head. Thus, when
the artesian pressure is lowered in an area of flowing wells by excessive
draft or by dry weather conditions, some wells cease to flow and all
wells vield less water.

SUBIRRIGATION
Subirrigation is the main method of irrigation used in Seminole County.
This method is made possible because of several factors including: rela-
tively level land, a layer of cemented sand (hardpan) from 3 to 5 feet
below the land surface, and a layer of sand above the hardpan which
absorbs and distributes the water.
Subirrigation is used to control the moisture in the soil so that the
plants will have adequate available water. An advantage to subirriga-
tion is that water in the soil can be effectively controlled so that soluble
fertilizers are not washed beyond the reach of the plants. Another ad-
vantage is that during periods of excessive rainfall the ditches used for
subirrigation can be used to drain the excess water from the ground and

















REPORT OF INVESTIGATIONS No. 27


I
>23
w
UJ


w

z

W 20


0
18

W

Z I

1 5
W
X


Well 84I-116-1 /

30



28-


27-


leof lion of discharge pipe

25 1


0 10 -20 30 40


Well 843-1d3-4
3in dlometer


12
I C --


Elevoion of dischoge pipe
10. 10 20 30 40 50 60 70 80 90


SWell 42-110-2
23 Zn. diameter
23 -- -- -- -- ~ ^ 7









17--










vod -p
19.---- ---






15--
ioeWlion of dischorge pipe
14 1 1 -


50 60 0 10 20 30 40 50
YIELD IN GALLONS PER MINUTE


60 70 80 90


Figure 12. Relation between the static head and the yield of four flowing artesian
wells in the eastern part of Seminole County.


I-
U)






FLORIDA GEOLOGICAL SURVEY


prevent waterlogging of the soil, which destroys some beneficial soil
bacteria and has other harmful effects.
The land is prepared for subirrigation by clearing and leveling. An
artesian well is drilled at the highest point, and the water from the well
flows into a concrete or terra cotta standpipe (supply pocket) that is
connected to a tile main. Lines of tile laterals 18 to 24 feet apart are
also connected to this tile main. A stop pocket is placed at the end
of each lateral, opposite the main. A short tile line connects this pocket
to an open drainage ditch or a large sewer tile which is used to drain
the water from the field. The level of the water in the field can be
controlled by the amount of water taken from the well, by plugging or
partially unplugging the heads of the laterals, or by controlling the
amount of water that is drained from the field. Additional information
on subirrigation can be obtained from the Agricultural Extension Service,
Gainesville, Florida. This method of irrigation uses very large quantities
of water.
WATER-LEVEL RECORDS
A total of more than 4,500 water-level measurements were made of
563 wells during the investigation. Most of these measurements and the
dates on which they were made are presented in table 1 of Florida
Geological Survey Information Circular no. 34.
Fluctuations of the water level are caused principally by pumping,
rainfall, and changes in atmospheric pressure. In order to obtain contin-
uous records of the changes in the artesian pressure head in Seminole
County, a water-level recorder was installed in 1952 on well 841-121-1,
about 1.25 miles west-southwest of Longwood, in an area of little ground-
water use. Another recorder was installed in 1952 on a flowing well
(well 847-113-6), about 2.8 miles southeast of Sanford, in an area of
extensive ground-water use.
Hydrographs for the two wells equipped with automatic water-level
recorders, and the monthly rainfall at Sanford, are shown in figure 13.
The most noticeable features on both hydrographs (fig. 13) are the high
water levels during the fall and winter of 1953 and the low water levels
during the spring of 1956. These features show near maximum and
minimum water-level conditions. The hydrographs of the two wells shown
in figure 13 correlate generally; however, after the high water levels
during the period of September to December 1953, the water level in
well 847-113-6 had reached the bottom of its sharp decline by the mid-
die of February 1954, but the water level in well 841-121-1 did not
reach a similar stage until the end of May. The hydrograph for well
847-113-6 shows more rapid fluctuations than the other hydrograph,








REPORT OF INVESTIGATIONS NO. 27


_J
-j
.47
cn
z46
w
S45

M44
S27
I-
w
u- 26
z


15
*z TOTAL= 47.62 TOTAL
OW(
7W 10

-- 5
na
a khHw


TOTAL = 45.60 TOTAL 53.05 TOT


1951 1952 I 1953 I 1954 I 1955 -1956

Figure 13. Hydrographs of the daily high water levels in wells 841-121-1 and
847-113-6 and the mdothly rainfall at Sanford.


SI I I.


'AL= 42.4f


4.06






FLORIDA GEOLOGICAL SURVEY


principally because of the large changes in the amount of ground water
used near well 847-113-6. Water levels in well 847-113-6 ranged from a
low of 19.58 feet above sea level to a high of 26.45 feet above sea level,
or a fluctuation of almost 7 feet. Water levels in well 841-121-1 ranged
from a low of 44.55 feet above sea level to a high of 52.49 feet above
sea level, or a fluctuation of almost 8 feet. These hydrographs show the
general trend of the water level during the period from 1951 through
1956, and they show also the relationship between rainfall and water
levels.
An important part of the investigation in Seminole County involved
comparison of current water levels with past water levels, to see if a
progressive decline in water levels had occurred. All the water-level
measurements were referred to mean sea level as a common datum for
comparison. When evaluating rainfall records to detect progressive
trends, it is essential to compare periods of similar rainfall. An inspection
of rainfall records at Sanford shows that the rainfall a few years prior to
1938 might be compared to the rainfall prior to 1955. Thus, the average
water levels on the hydrographs for the years 1937 and 1954 can be
compared. Most of the difference in water levels between these 2 years
can be attributed to factors other than rainfall differences.
Figure 14 shows the hydrographs of five wells and the monthly rain-
fall at Sanford. These hydrographs include measurements made in 1933
and 1935 by V. T. Stringfield, in 1937 by S. A. Stubbs, and in 1939 by
Irving Feinberg. Well 846-116-11 is 2.9 miles south of Sanford near the
north edge of Lake Ada and near the city of Sanford well field. The hydro-
graph shows a fluctuation of about 6 feet for the period of record. The
data on the graph show that the water level has probably declined about
1 or 2 feet since 1937. Some of this decline might be the result of an
increase in pumpage by the city of Sanford from an average of 0.67 mgd
(million gallons per day) in 1938 to an average of 1.54 mgd in 1956.
Well 844-117-2 is 4.9 miles southwest of Sanford, near Elder Spring.
This well shows water-level fluctuations similar to those of well 846-116-
II. Well 843-118-2 is 5.9 miles southwest of Sanford and about one-fourth
mile south of Five Point.?, or the junction of U. S. Highways 17 and 92
and State Highway 419. The hydrograph for this well shows a general
decline in water level of 2 or 3 feet between 1935 and 1956. The 1935
water levels in both 844-117-2 and 843-118-2 are less than 1 foot below the
water levels measured in the fall and winter of 1953, the highest water
levels of record.
The hydrograph of well 842-117-2, at Wagner (south of Lake Jessup),
shows the 1933 and 1935 water levels to be approximately the same as







REPORT OF INVESTIGATIONS No. 27


WELL 841-11 3-1
3A -I|
TOTAL TOTAL TOTA. L TII TOTAL TUTAL AL
S4MB 5 4L" T 9W SL t 4TAIR 4S 5M0 4f4
14
i2






Figure 14. Hydrographs of wells 841-113-1, 842-117-2, 843-118-2, 844-117-2,
846-116-11, and the monthly rainfall at Sanford.








FLORIDA GEOLOGICAL SURVEY


30 ---

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3<4------
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II__ __H WELL 849-118-5 ll'
30 MILES NORTHWEST OF SANFORD
I I I I








-- WELL 848-119-4,
L2 MILES SOUTH OF LAKE MONROE









5.2 MILES SOUTH OF SANFORD






WELL 840-112- 1"
0.3 MILE NORTH OF OVIEDO











WELL 839-113-1,
1.2 MILES SOUTHWEST OF OVIEDO


Figure






REPORT OF INVESTIGATIONS No. 27


those of 1955 and 1956. The hydrograph of well 841-113-1, 1.6 miles
northwest of Oviedo, shows a water-level decline of 2 or 3 feet between
1937 and 1956. The water levels in 1937 are only about 1 foot lower than
the high water levels during 1953. The 2- or 3-foot decline might be
caused by the increased number of wells and the corresponding increased
use of ground water in the farming area north of Oviedo.
Hydrographs of six wells are shown in figure 15. Well 849-118-5, 3.0
miles northwest of Sanford, and well 848-119-4, 1.2 miles south of Lake
Monroe, both show water-level fluctuations of almost 8 feet. The hydro-
graphs do not show any significant trend of water level over the period
1933-56.
The water level in well 844-115-8, 5.2 miles south of Sanford, fluctu-
ated less than 6 feet during the period of record and declined about 4
feet between 1933 and 1956. This decline is probably due to increased
use of water in the vicinity. The hydrograph of well 844-115-8 shows that
the water level during 1937, a year with nearly normal rainfall, was
almost 2 feet higher than the highest water level measured in 1953, the
year of the highest rainfall ever recorded at Sanford.
Another well that shows. a general water-level decline of about 3 or 4
feet for the period of record is well 840-112-1, 0.3 mile north of Oviedo.
The hydrograph of this well and the hydrographs of wells .839-113-1
and 838-113-2 show evidence of increased use of water around Oviedo
since 1937. Well 839-113-1, 1.2 miles southwest of Oviedo, is in an area
of extensive ground-water use and has water-level fluctuations as large
as 9 feet within short periods of time. These rapid changes in water level
tend to mask out any general trend in the water level. Well 838-113-2,
at Slavia, shows a water-level decline similar to that shown by well
840-112-1.
Hydrographs of 10 other wells that show past records of water levels
are included in the section.of this report entitled "Salt-Water Contami-
nation."
An illustration of the relationship of the water level in an artesian
well to the water level in a nearby nonartesian well is shown on figure
16. These wells are about 1% miles west of Paola, in an area of very
little ground-water use. Most of the water-level changes, therefore, are
due to variations in the amount of rainfall. The artesian well obtains
water from the Hawthorn Formation and the nonartesian well obtains
water from the Pleistocene sands.
The hydrographs for the two wells show similar fluctuations. The
elevation of the water level in the nonartesian well varies from 3.5 to 6
feet above the water level in the artesian well. Therefore, the shallow







FLORIDA GEOLOGICAL SURVEY


0i 50
iL.
< 48
U0
S46

u. 44
o
42
I-

U- 40
z

L-t

I3
58

3E


Figure 16. Hydrographs of wells 846-123-2 and 847-123-2, about 1% miles
west of Paola.

sand aquifer probably recharges the Hawthorn Formation in this area.
The shallow well had a maximum water-level fluctuation of 8 feet and the
deep well had a maximum water-level fluctuation of 6 feet during the
period of record shown in figure 16.

SURFACE WATER
SPRINGS
Seminole County has several large artesian springs and several small
nonartesian (water-table) springs. Most of the artesian springs are along
the Little Wekiva or Wekiva rivers. These include Sanlando Springs, Palm
Springs, and Sheppard Spring, all about 8 miles west of Longwood and
along the Little Wekiva River.
ARTESIAN SPRINGS
Sanlando Springs is in the NESE3 sec. 3, T. 21 S., R. 29 E., on
the east bank of the Little Wekiva River. The springhead forms an
irregularly shaped pool about 50 feet in diameter. Ferguson, et al.,
(1947, p. 149-153) gives descriptions and data about Sanlando, Palm,
and Sheppard springs. The temperature of the water from Sanlando
Springs was 74F, and the maximum depth of the water at the spring-
head was 13.2 feet on April 23, 1946. The average of three discharge
measurements of the spring is 18.4 mgd. Table 4 and figure 33 show an
analysis of the water from Sanlando Springs. The water is moderately
hard and similar to water found in most artesian wells in the southwest


SWELL 847-123-2
Nonortesian well,
V 8 feet deep




WELL 846-123-2
Artesian well,
70 feet deep

1953 1954 1955 1956


I






REPORT OF INVESTIGATIONS No. 27


section of Seminole County. It is classed as a calcium bicarbonate
water and the total hardness (as CaCO3) was 105 ppm.
Sheppard Spring is in the SWNW', sec. 2, T. 21 S., R. 29 E., 0.2
mile north of Sanlando Springs. The spring forms a pool about 70 to 80
feet in diameter. The temperature of the water was 74F. and the
yield was 11 mgd on July 25, 1944. Chemical analysis of the spring
water collected on the above date shows the water to be very similar
to the water from Sanlando Springs, having a mineral content only
slightly higher. The spring is used as a private swimming pool by the
owner.
Palm Springs is in the SWfNW, sec. 2, T. 21 S., R. 29 E., 0.3 mile
north of Sanlando Springs. The pool, formed by concrete retaining walls,
is rectangular. The flow of the spring was 6.3 mgd on November 12,
1941, and 6.7 mgd on August 25, 1954. The spring is used for swimming.
Miami Springs is in the NWhNW, sec. 32, T. 20 S., R. 29 E., 0.25
mile south of the Wekiva River. The spring forms an oblong pool which
is used as a private swimming pool. Florida Geological Survey Bulletin
No. 31 (Ferguson, et al., 1947, p. 179, table 4) gives data on Miami
Springs but incorrectly lists the spring in Orange County. The flow
of the spring was 3.7 mgd on August 8, 1945.
In the spring of 1957 land-clearing operations helped develop a
new artesian spring in Seminole County. The spring is 0.4 mile southeast
of Miami Springs and is called Sweet Water Spring. The spring, shown
in figure 17, is in the NW, sec. 32, T. 20 S., R. 29 E., 100 feet north of
the Wekiva Spring Road and about 25 feet west of Sweet Water Creek.
Figure 17a shows the springhead pool and the short run into Sweet
Water Creek, and figure 17b shows a closeup of the spring pool, which
is about 8 to 10 feet in diameter, and the turbulence of the boil. The
total flow of the main spring and several much smaller springs is estimated
to be about 100 gpm.
A similar spring developed in the NENE,4 sec. 36, T. 20 S., R. 30 E.,
about 100 feet south of Lake Jessup, in the spring of 1952. This
spring, which was developed by dredging a small boat basin on prop-
erty owned by William Crook, flowed about 2 mgd shortly after it
formed. An attempt was made to measure the flow on November 4,
1952, but no measureable flow could be detected.
The water level in well 842-116-4, 700 feet south of the spring, was
39.78 feet above sea level on May 14, 1952. The well was measured on
May 28, 1952, 3 days-after the spring began flowing, at which time the
water level was 35.62 feet above sea level. Most of the 4-foot decline of
water level was probably caused by pressure relief due to flow of the










FLORIDA GEOLOGICAL SURVEY


a'~;~'~.-~ry;i~""~i~i"~l~-~Ti~F~+
-



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REPORT OF INVESTIGATIONS No. 27


: .. ..: ,- T ,. -. -:

-



b, closp view of -spring
.. -- i ,..__. -L ,t

b, closeup view of spring.


I~cssR- _~_~~
--- ~t~F
~cr
~F~-~
c~s~a~r


RO







FLORIDA GEOLOGICAL SURVEY


Figure 18. Heath Spring, 0.7 mile northwest of Geneva.







REPORT OF INVESTIGATIONS No. 27


spring. At well 842-116-1, 0.65 mile southwest of the spring, the water
level declined 3 feet from April 4, 1952, to May 28, 1952.

WATER-TABLE SPRINGS
Elder Spring is in the NEO NW, sec. 23, T. -20 S., R. 30 E., about
5 miles south of Sanford. The flow of the spring is rather small, and a
small pump and motor delivers the water to a building where it is
bottled for sale. The chemical analysis of Elder Spring water is shown
in figure 33 and table 3. The water is very soft, as the total hardness
(as CaCo3) is only 29 ppm and is classed as a calcium bicarbonate type.
Heath Spring is in the SW4 sec. 16, T. 20 S., R. 32 E., 0.7 mile north-
west of Geneva. The yield of the spring ranges from 5 to 10 gpm, and
the water is occasionally used for drinking purposes and in storage
batteries. Figure 18 shows a view of the main spring pool. A chemical
analysis of the water, which is classed as a sodium chloride type, is
shown in table 3 and figure 33. The water is very soft, the total hardness
(as CaCo3) being only 7 ppm. Figure 19 shows the temperature and the


z _V
w--
o 50
-)




a 72[

70
ta
o 68----
C --

66 1952 1953 1954 1955 i 1956

Figure 19. Temperature and chloride content of Heath Spring.

chloride content of water from Heath Spring. The water temperature
ranges from 66 to 740F. and varies according to the seasonal temperature
changes. The chloride content ranges from 12 to 26 ppm and is probably
influenced by the amount of rainfall and the direction of winds, which
carry salt spray from the ocean.
LAKES
Water-level measurements of five lakes in Seminole County (fig. 20)
were made for comparison with rainfall records, norartesian water levels,
and artesian water levels.
Lake Geneva, half a mile east of Geneva, had the largest fluctuations







FLORIDA GEOLOGICAL SURVEY


87
/ PRAIRIE LAKE




85
. A 1 ________ _______ -- ^ __ r ^ ________- ____ ^ __


-1
Lii
11U


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cr)

z
LLi



0
LL1


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57

56



43" LAKE MARY

4*2 -,

41





LAKE JENNIE




35-----

34!

29
LAKE GENEVA






23
27------ ^-----









22-

I I It l II I II 1 1 1 1 1 1 1 I I I lll 1 1 1 1 I I I II 1 1 1 I I I III I I I I
1952 1953 1954 1955 1956
Figure 20. Hydrographs of five lakes in Seminole County.






REPORT OF INVESTIGATIONS No. 27


of any lake measured. Measurements begun in the fall of 1953 and
continued through 1956, indicate a fluctuation of almost 7 feet during
this period. The lake levels ranged from a high of 28.2 feet above sea
level to a low of 21.5 feet above sea level. During the period of record,
the lake level was from 2 to 6 feet higher than the water level in nearby
artesian wells, indicating that the water of Lake Geneva is obtained
mostly from the nonartesian aquifer and in part directly from rainfall
that falls on the lake. Figure 21, a photograph of Lake Geneva taken
on August 13, 1957, shows a small boat dock that was unusable owing
to the low water level at that time.
Lake Jennie, about 2 miles south of Sanford, had a fluctuation of less
than 2M feet during the period 1952-56 (fig. 20). The lake level usually
stands from 4 to 7, feet higher than the water level in well 847-116-1,
an artesian well half a mile north of the lake. The water level in the
lake stands from 7 to 10 feet higher than the water level in well
847-116-2, an artesian well 0.8 mile northeast of the lake, and from
0.8 foot below to 3.5 feet above the water level in well 846-116-11,
an artesian well 0.3 mile south of the lake. The artesian pressure head
in well 846-116-11 was. higher than the lake level for only a few months
during the fall of 1953. Most of the time, the lake level stands above
the piezometric surface.
Lake Mary, about 0.2 mile southeast of the town of Lake Mary,
fluctuated more than 4 feet during the period of record. At different
times, the lake level stood either above or below the water level in
well 845-119-1, an artesian well 0.25 miles northwest of Lake Mary.
During wet periods the lake level was as much as 3 feet lower than
the piezometric surface, and during dry periods, the lake level was as
much as 2 feet above the piezometric surface. During dry periods, there-
fore, the lake is a potential source of recharge to the artesian aquifer,
and during wet periods the artesian aquifer could contribute water to
Lake Mary.
Lake Orienta, half a mile west of Altamonte Springs, fluctuated less
than 4 feet during the period of record. Figure 22 shows a comparison
of the lake level with the water level in artesian well 840-120-2, 1.6 miles
east of the lake, and the water level in nonartesian well 839-122-1, 650
feet northwest of the lake. The lake level is generally about 2 to 4 feet
higher than the water level in the artesian well, except during very wet
periods when the water-level altitudes are about the same. However, in
an artesian well (839-121-5) 400 feet north of Lake Orienta, the water
level was below the lake level during both wet and dry periods. The
lake level was generally 2 to 4 feet above the water level in the non-
artesian well (839-122-1).















1:~" ~ rI r


Figure 21. Lake Geneva showing the low water level on August 13, 1957.



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REPORT OF INVESTIGATIONS No. 27

61

60

59

58
58LAKE ORIENTA,
Q5 MILE. WEST OF ALTAMONTE SPRINGS
57-

56
51 --- i ------------ --- ---
61

60

59 /L
/
58

57 -- i

56 /
Ariesion well
55

54

53
WELL 840-120-2, 1.5 MILES FROM LAKE
ORIENTA AND 0.5 MILE SOUTHWEST OF FERN PARK
52
59

58

57 1

56

55
Nonartesian well
54

53
WELL 839-122-1, 700ft FROM LAKE ORIENTA AND
0.8 MILE WEST OF ALTAMONTE SPRINGS
52 1937 1951 1952 1953 1954 1955 1956
Figure 22. Hydrographs of wells 839-122-1, 840-120-2, and Lake Orienta.


I






FLORIDA GEOLOGICAL SURVEY


Prairie Lake, 0.3 mile southeast of Altamonte Springs, fluctuated
about 3 feet during the period of record. The lake level is about 30
feet higher than the piezometric surface in the vicinity.
WELL EXPLORATION
ELECTRIC LOGS
The electric log is a very useful aid in the identification of formations
penetrated by a well and of fluids these formations contain. However,
in limestone formations of the Floridan aquifer, electric logs preferably
should be interpreted in conjunction with other aids such as well cut-
tings or drilling time logs. The electric log is a graph of the electrical
properties of the rocks and fluids penetrated by the well. The electrical
resistivity and self-potential are recorded with the depth as the abscissa
of the graph.
Electrical resistivity is a measure of the resistance of material to
the flow of an electric current. The term "relative resistivity" is used in
this report because the electric logging equipment used was the single-
electrode type which does not yield precise results.
Water is the main fluid that fills the void spaces in the limestone
sediments and conducts electricity. Pure water has a very high resistivity
but ground water has a much lower resistivity because of its dissolved
mineral content. In general, in Seminole County, high relative resistivity
indicates dense sediments that yield little water.
In Volusia County, Wyrick and Leutz (1956, p. 23) found a cor-
relation between the dense layers of limestone, high relative-resistivity
readings, and increased drilling time. These dense layers of limestone
generally restrict the vertical movement of water. The application of the
resistivity curve of electric logs made of limestone aquifers in Seminole
County has been limited to the location of porous and dense sections in
the limestone and to the determination of other lithologic changes.
The self (spontaneous) potential measures the difference in voltage
between an electrode in the well and a ground at the surface. The
potential differs according to the nature of the beds traversed. The self
potential log is used to distinguish between permeable and impermeable
deposits. In some wells the self-potential curve shows a difference be-
tween fresh and salty water. As the open-hole part of the wells logged in
Seminole County was in limestone, the self-potential curves yielded
little information.
RESISTIVITY, FLOW, SALINITY, AND TEMPERATURE MEASUREMENTS
Figure 23 shows an electric log, a current-meter traverse, and salinity
measurements in well 845-117-10, about 3.6 miles south of Sanford. The







REPORT OF INVESTIGATIONS No. 27 45


1 Z RELATIVE RESISTIVITY E ON
SELF POTENTIAL Ohm-melersen meter) (ppm)
40 IOv 0 10 20 2 30 4 50 0


20

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z_
--220



-20
<-260- I ------- -- ------------
w

o 2










-Obstruction.
340 Well 845-117-10

Figure 23. Electric log, current-meter traverse, and chloride content of water from
Swell 845-117-10, 3.6 miles south of Sanford.
;well 845-117-10, 3.6 miles south of Sarford.






FLORIDA GEOLOGICAL StUVEY


most noticeable feature of the relative-resistivity graph is the highly
resistant zone at 290-300 feet below sea level, which represents a dense
layer of limestone. This dense layer probably is relatively impervious,
and restricts the vertical movement of water. The relative-resistivity
graph was useful to the city of Sanford, as it contributed to the decision
to deepen some city wells in the spring of 1956 when additional quanti-
ties of water were required. The Sanford well field is about half a mile
east of well 845-117-10. Before 1956, the wells were not deeperied be-
cause of the possibility of obtaining salty water. After exploring well
845-117-10, it appeared that the city wells could be deepened to about
280 feet below sea level without increasing the chloride content of the
water. The confining layer would prevent salty water, if present at a
lower depth, from moving upward and contaminating the water in the
producing zone. Four wells in the field were deepened as much as 100
feet without any increase in the chloride content of the water. Thb
bottom of the deepest city well is 180 feet below sea level.
The flow graph in figure 23 shows a slight flow in the well, although
the well was not flowing at the surface. The current-meter revolutions
were so slow that it was not possible to determine whether the flow was
upward or downward. The chloride content of water samples collected
at various depths in the well was relatively constant.
Similar information from well 840-107-2, about 2.1 miles north of
Chuluota, is given in figure 24. It shows a layer of very dense limestone
at about 340 to 365 feet below sea level. This dense limestone acts as
a confining layer for the salty water below. The chloride content of water
from the limestone below this dense layer is much higher than the
chloride content of water from the limestone above the layer, presumably
because the lower aquifer has not been flushed as completely as the
upper aquifer.
The velocity graph shows that most of the water was coming from
a very productive zone just below the dense layer. Even if the flow
of water is constant within the well, variations in the velocity graph
can be due to irregularities in the well diameter. Such irregularities
are probably responsible for the apparent differences in flow. The velocity
is more uniform in the cased part of the well, where the diameter of
the well bore is constant; however, the diameter of the rest of the
well bore differs because of caving of some of the relatively unconsolidated
rocks penetrated by the well. However, the velocity declines as the
water moves up the cased part of the well. This may be due to loss of
head by pipe friction and as a result of lifting the water to the surface
or small leaks in the casings. The chloride content of the water collected







REPORT OF INVESTIGATIONS No. 27 47





0. -- --- WM---- IV

l..,w .eu. "__.l /

-0 --
0


-40c


-60





S-100
i -2 -_i

4




200 -

.220 -





2401











Figure 24. Electric log, current-meter traverse, and chloride content of water f on
-300. U

-320 lie

.340 IL


0 befrucelon
-3600

Well 840-M17-2

Figure 24. Electric log, current-meter traverse, and chloride content of water fioni
well 840-107-2, 2.1 miles north of Chuluota.



at the surface was lower than the chloride content of water samples
collected within the well. This may be due to a small error in the field
determination of the chloride content of the water sample collected at
the surface.
The graph of the relative resistivity in well 848-116-12 (fig. 25),
about half a mile southwest of Sanford, indicates a dense layer of lime-
stone at about 250 feet below sea level. This may be the same hard
layer that is 40 to 50 feet lower in well 845-117-10 (fig. 23). The well
was not flowing at. the time of exploration and the current meter did not







FLORIDA GEOLOGICAL SURVEY


SELF POTENTIAL
S10 my


RELATIVE RESISTIVITY
Ohm-meters
9 5 p 15


CHLORIDE
CONTENT
(ports per million)
50 400 4!


20



0-

-20-


______________________ II


Well 848-116-12


Figure 25. Electric log and chloride content of water from well 848-116-12, 0.5 miles
southwest of Sanford.


I So


-------_ -----

i!








40
















Li y
z

0


IL





a
0
a. ---- --------- -_------- --

a
z


-1

LU
-60
_:
-80










-160-
z







cr_
-140

U-I
a -160


LU -180


LU -200


z -220


1 -240-


-260-


-280-


-300-


-320-


-340-


-36C


I







REPORT OF INVESTIGATIONS No. 27


indicate any movement of water within the well. The chloride content
of the water collected within the well did not show any significant
change at various depths in the uncased part of the well. The electric
log contained some unusual graphs in the cased portion of the well. As
the well is old and unused, the graphs might represent corroded zones
or holes in the casing. Water leaking through these holes might explain
the higher chloride content in the cased portion of the well.

A combination graph of well 841-110-12, about 2.7 miles northeast


of Oviedo, is shown in


20

j0-
LL2.




-2
n -40-






-I0
w
Li-

w-
w -14

U-
0 -180





w
F-I80-
I-14
K-160


J-200


, 2


SELF POTENTIAL
IOmv


figure 26. The graph of


RELATIVE RESISTIVITY
Ohm-meters
5 10 15 20


the relative resistivity


VELOCITY
rev/sec of current meter j
0.5 1.0 15


Well 841-110-12
Figure 26. Electric log, current-meter traverse, and chloride content of water from
well 841-110-12, 2.7 miles northeast of Oviedo.


indicates that the resistivity of the rocks increases generally with depth.
The velocity graph shows that most of the flow apparently comes from
the uppermost 20 feet of limestone below the bottom of the casing.
The lower part of the well contributes only a very small amount of water
and the bottom 40 feet of the well apparently contributes none. The
chloride content of the water collected at various depths within the well


CHLOR


3 t



U 1
o z

It






1 Z






."






50 FLORIDA GEOLOGICAL SURVEY


showed no difference except in the sample from the bottom of the well,
which contained about 55 ppm less chloride than the four shallower
samples. This bottom sample was collected in the zone of no measurable
flow.
The graphs for well 838-113-3, about 2.5 miles southeast of Oviedo
(fig. 27), show that almost all the water is obtained from the uppermost


_j 20-
LJ
LJ 0-
--

S-20

z2 -40
ULi
M -60
0
-80
0
LI
g -loo-
LU
S-420

L -140-
L.

Z -160.

0 -180-
t-

4


I4z
,


SELF POTENTIAL


RELATIVE RESISTIVITY
Ohm -meters
25 50 75 100


VELOCITY
ev/sec of current meter)
o 0.5 1.0 L


IU
0Z.




Orut I !






53













Obstruction
r'?. __. ^__ !


WELL 838-113-3
Figure 27. Electric log and current-meter traverse in well 838-113-3, 2.5 miles
southeast of Oviedo.

80 feet of limestone below the bottom of the casing. The graph of the
relative resistivity shows that many thin, dense layers are present in the
limestone. Most of the flow seems to be obtained from the areas of low
resistivity.
The combination graph of well 842-111-6, about 2.3 miles northeast
of Oviedo (fig. 28), shows that most of the water is obtained from



















S_______ ___ '"" De ti wtell Dfptiof wll
Kat -ot iatlre n X
lo I n r ment a ade men wa mad
Sample taken In
-coam lted wall.



I-__ r

















WELL 42- 111-6

Figure 28. Electric log, current-meter traverse, chloride content, temperature, and
yield of water from well 842-111-6, 2.8 miles northeast of Oviedo.

Ux
'.4





FLORIDA GEOLOGICAL SURVEY


the Hawthorn Formation. The rest of the water is obtained from the lime-
stones of the Ocala Group. Below the bottom of the casing, the points of
higher velocity correspond with the layers of higher relative resistivity.
These more resistant layers are hard and they are affected very little by
caving; the well diameter, therefore, is generally smaller at these layers.
The smaller diameter of the well bore restricts the flow and increases
the velocity of the water.
A study of the current-meter traverse in the cased part of the well
indicates that the casing may be leaking somewhere in the zone from 30 -
to 45 feet below sea level. The current-meter revolutions decreased from
3.2 per second at 45 feet below sea level to 2.0 revolutions per second
at 30 feet below sea level. The velocity measurements within the casing
were more uniform in the other wells that were explored.
Measurements of the chloride content of the water were taken at
various depths within well 842-111-6 by two different methods. One set
of water samples was collected from the bottom of the well with a bailer
while the well was being drilled. The chloride content of these bottom-
water samples increased from 450 ppm in a sample collected at 55 feet
below sea level to 755 ppm in a sample collected at 190 feet below sea
level. These samples were collected during the period January 12-27,
1963- On December 3, 1956, water samples were collected at various
depths within the well. The chloride content of these samples ranged
from 900 to 960 ppm. The composite sample of the chloride content of
water collected at the surface was about 200 ppm above the highest
chloride content measured while the well was being drilled in 1953.
The discharge temperature of the water, while the well was being
drilled, increased from 74.50 to 76.50F. from the bottom of the casing
to the bottom of the well. This amounts to an increase of about 1F. in
the temperature of the water discharged for every 60 feet increase in
well depth. However, these temperature measurements were made of
the water discharged at the surface and .do not represent the actual
temperature of the water at depth in the well.
The graph of the increase in yield shows that the first flow of water
was 50 gpm when the bottom of the well was 53 feet below sea level.
The yield increased to almost 400 gpm during the next 12 feet of drilling.
The well yield at the surface was 670 gpm when the well was completed.
Almost 4 years later, the well yield was 700 gpm.
The graph of the relative resistivity of the rocks at well 847-113-31
(fig. 29), about 3.0 miles southeast of Sanford, indicates many thin resis-
tant (dense) layers in the Avon Park Limestone. The graph of the
chloride content of water samples collected within the well shows an






REPORT OF INVESTIGATIONS No. 27


WELL. 847-113-31

Figure 29. Electric log and chloride content of water from well 847-113-31, 3.0
miles southeast of Sanford.


-I
_J
>
LU
-J
_2









0
I-
ZW



LU

rr
LU
LJ
L-



LU

Z

Li
D
I-
-J





FLORIDA GEOLOGICAL SURVEY


increase of chloride content from 650 to 675 ppm as the depth increased
about 90 feet. The well was not flowing at the surface when the water
samples were collected. An attempt was made to determine if the well
had any internal movement of water but an obstruction prevented the
current meter from being lowered more than 23 feet below the surface.
Figure 30 shows the amount of casing, the depth, and current-meter
traverses for two wells near Oviedo. Well 842-112-2, about 2.3 miles


WELL 842-112-2 WELL 842-111-7
Figure 30. Current-meter traverse and chloride content of water from wells 842-112-2,
2.3 miles northeast of Oviedo, and 842-111-7, 2.3 miles northeast of Oviedo.

northeast of Oviedo, has about 65 feet of open hole in the Floridan
aquifer below the bottom of the casing. The bottom measurement of
the current meter in this well indicated a substantial flow which
increased upward to the bottom of the casing.
The graph of the velocity in well 842-111-7, about 2.3 miles northeast
of Oviedo, shows a small flow in the bottom 25 feet of the well. Most
of the flow, however, is obtained from the zone between 100 and 180 feet
below sea level. The chloride content of the water discharging at the
surface was 1,300 ppm. The chloride content of water samples collected
within the well ranged from 1,270 to 1,345 ppm. The sample at the





REPORT OF INVESTIGATIONS No. 27


surface represents a composite of the chloride content of water
obtained from all the producing zones within the well.

QUALITY OF WATER.
The wide range in the chemical composition of ground water in Semi-
nole County is shown by analyses of samples of the water. Some of the
ground water is excellent for ordinary use and some cannot be made
suitable for general use by any practical treatment.
The amount of dissolved mineral matter in water from the Floridan
aquifer ranges from low in the recharge areas of the hilly uplands to high
in the discharge areas of the lowlands. Stubbs (1937, p. 27) concluded
that the highly mineralized water in Seminole County was coming from
the Coskinolina Zone (Avon Park Limestone). Information collected
during this investigation has shown that the area in which the well is lo-
cated is more important in regard to the dissolved solids content of water
than the geologic formation that the well penetrates.
Samples of ground water for chemical analyses were collected in every
section of the county, but the most intensive sampling was done in
the areas. in which the water is highly mineralized. These areas gener-
ally include most of the areas of artesian flow. The chemical analyses were
made by the Quality of Water Branch of the U. S. Geological Survey.
The dissolved chemical constituents of water are reported in parts per
million (ppm). A part per million is a unit weight of a constitutent in a
million unit weights of water. Thus, a water sample containing 1 ppm of
iron (Fe) contains 1 pound of iron in a million pounds of the water sam-
pled. In order to show water analyses graphically, the cations and anions
may be expressed in chemically equivalent weights or equivalents per mil-
lion (epm); parts per million may be converted to equivalents per million
by dividing the parts per million by the combining weight of the respec-
tive cation or anion. Specific conductance is reported in reciprocal ohms
mhoss); pH is reported in standard pH units; and color is reported in
dimensionless units defined by the standard platinum cobalt scale.
The mineral constituents of natural waters generally reflect the com-
position and solubility of the rock materials with which the waters have
been in contact. In Seminole County, the minerals found in ground water
are not obtained entirely from rocks and soils. Some of the mineralization
of ground water in Seminole County probably comes either from sea
water that entered the rocks during the interglacial periods of the
Pleistocene Epoch, or from sea water that was trapped in the rocks when
they were deposited.





FLORDA GEOLOGICAL SURVEY


COLOR
Color in water may be of natural mineral, animal, or vegetable origin.
It may be caused by metallic substances, humus material, peat, algae,
weeds or protozoa. Industrial wastes may also cause color; color may
range from zero to several hundred units. Although color is not harmful
to people, it is objectionable when present in noticeable amounts. Color
begins to become undesirable in quantities above 20. All except 2 of
the 22 samples on which color determinations were made had a color of
less than 10. Color determinations of 22 ground-water samples in Seminole
County ranged from 1 to 25 (table 4).

SPECIFIC CONDUCTANCE
The specific conductance is a measure of the ability of the water to
conduct an electric current. The more dissolved mineral matter in the
water, the better it will conduct an electric current. Thus, specific con-
ductance indicates in a general way the relative mineralization of the
water. The specific conductance of 179 ground-water samples in Seminole
County was found to range from 135 to 21,900 micromhos at 250C.
(table 4).
SILICA
Most silica (SiO2) in water is probably derived from silicate minerals
other than quartz. Silica is of little significance in the range normally
found except when the water is used for boiler feed water. A recom-
mended upper limit of silica for boilers operating at 400 pounds per
square inch or above is 1.0 ppm (Rainwater and Thatcher, 1960, p. 259).
Silica in 20 ground-water samples in Seminole County was found to range
from 7 to 21 ppm.
IRON
Iron (Fe) is dissolved from almost all rocks and soils by rainwater
and ground water during the process of weathering. In addition, some of
the iron detected in ground water may have been dissolved from the well
casing and pipes. A concentration of more than about 0.3 ppm of iron in
water is objectionable, as it stains porcelain, plumbing fixtures, and
clothing. It imparts an undesirable taste, and oxidation of the iron forms
a reddish brown sediment. Excess iron can usually be removedby aeration
and filtration but some waters require more elaborate treatment.
The concentration of iron in the ground waters of Seminole County
differs considerably from place to place. The highest iron concentrations
are in artesian water from wells drilled in the lake regions. The presence
of a considerable amount of iron is usually associated with the presence
of a nearby recharge area. The total iron content in 38 ground-water
samples in this area ranged from 0.00 to 5.9 ppm. Many of the shallow






TABLE 4. Chemical Analyses of Water from Wells in Seminole County
(Analyses in parts per million, except specific conductance, color, and pH, by U.S. Geological Survey)

Hardness
Dis- as CaC03 Specific
solved con- Hy-
Date of Cal- Mag- Potas- Bicar- Sul- Chlor- Flu- Ni- solids duct- drogen
Well No. collection Silica Iron cium nesium Sodium slum bonate fate ide oride trate (residue Cal- ance Color pH sufide
(8i02) (Fe) (Ca) (Mg) (Na) (K) (HC03) (S04) (Cl) (F) (NOa) at cium Non- (mi- (HaS)
180C.) mag- car- cromhos
nesium bonate et250C.)


1 1 2


836-102-1
836-107-1
836-113-1
836-117-1
887-101-1
837-102-1
837-102-8
837-102-3
837-103-1
837-103-2
837-109-1
837-114-1
887-115-1
837-119-2
88-103-1
838-106-1
838-106-2
838-107-1
838-113-3
838-113-3
838-115-2
838-116-2
838-120-1
883-121-4
838-123-1,
838-125-1
8838-126-1
839-102-1
839-104-1
839-109-1


2- 3-55
3- 1-54
2- 7-55
3- 1-54
11- 4-53
3- 1-54
2- 3-55
6-23-56
6-23-56
6-223-56
2- 7-55
8- 1-54
3- 1-54
2- 5-55
3- 1-54
3- 1-54
2- 7-55
11- 5-53
11- 5-53
6-23-56
2- 5-55
2- 5-55
6-25-56
2-26-54
2- 3-55
2-24-54
2-24-54
2- 2-54
2- 2-55
3- 1-54


3



......

15












12
10
......


4

...'..,


0.21



.46
.14







.....45
.12



..,6




,...,.


5

148
58
43
29
164
97
100



50
34
26
43
134
53
39
46
36

36
56
44
45
30
22
148
84
49


6 7 8 9


66
1.7
9
11
71
29
43



8
7.3
1
7.4
75
5.1
1.8
2.6
8.8

8.3
3.4
5.1
12
16
11
86
33
16


..ii...
11
13
.,..,,.


,......
.6
.9
,,..


312
264


153
142
,....,


10

318
1.0
2.0
8.0
348
132
180



6.5
1.0
1.0
2.0
306
4.0
2.0
1.5
8.0

10
2.0
,...,,,
1,0
2.0
2.0
4.0
338
112
25


11

815
8
8
7
930
308
460
.... .
12
80
12
8
6
7
1,010
7
9
18
24

8
8
7
5
6
8
9
1,140
435
185


12 13


0.1



.0
.0








.1






..,...


2.0












1.1
,....,


14 15

2,100 650
180 152
170 144
140 116
2,360 701
900 362
1,200 425



190 158
150 115
88 69
170 138
2,400 642
180 153
130 104
164 125
176 126

100 124
190 154
160 131
200 164
160 140
140 106
1,700 725
1,100 345
530 190


16





547













10
....,,


17

3,320
303
292
242
3,720
1,520
2,070
494
570
325
251
151
288
3,880
304
231
296
311

268
324
447
269
351
275
236
4,420
1,860
800


. ....
.,....

......
,o,....
,..,...
..,...


. ,. ...,
6
6
o.. .


18 19 20


8.0
7.8
7.9
7.6
7.6
7,3
7.7



7.9
7.8
7.8
8.0
7,4
7.8
8.2
7.6
7.6

7.7
8.1
8.1
8.5
7,7
7,9
7,6
7.7
7.9


12
248
.. 6

.. '6


514












TA~IE 4. (Contintued)


7 8 U


13 11


839-113-1
839-116-1
839-120-1
830-120-4
839-125-1
830-125-2
840-103-2
840-107-3
840-108-1
840-110-8
840-112-2
840-115-1
840-117-4
840-118-1
840-119-1
840-120-3
840-124-1
840-125-3
841-106-1
841-109-2

841-110-1
841-110-2
841-110-5
841-110-5
841-110-0

841-110-9
841-110-12
841-110-12
841-111-1
841-112-2

841-113-1
841-114-1
841-118-2
841-120-2
841-120-5
841-122-1
841-125-1
842-100-1
842-100-2
842-107-1


3- 1-54
2-2-654
2-a2-54
1-25-511
(1-25-51

4-10-52
3- 1-54
3- 1-54
2- 3-55
2- 5-55
3- 1-54
2- 5-55
6-25-50
2-26-54
2-26-54

11- 5-53
2-24-54
2- 3-55
11- 4-53
2- 5-55

3- 1-54
3- 1-54
2- 5-55
0-23-50
11- 5-53

0-23-50
11- 5-53
0-23-56
2- 5-55
3- 1-54

2- 5-55
2- 5-55
2- 5-55
6-25-50
7- 6-56

2-24-54
2- 3-55
3- 1-54
3- 2-54
3- 1-54


. ., .i. ..
1.7

11 .08






S3.


11 .31






. .. .. .. .
...... ......
...... ......
...... ......






















...... ......23
0

...... .......
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17 1 18 1u I 20


8. 1


o. . .

,,....,

0,2
,.,,,,
,,,,,,


S 32 3 4


5

53
3u
50


26
143
04
48
58
44
38
29
32

40
31
14
08
104
82
01
90
94
102

04

43
53

43
44
29

28.7
27
33
42
43
78


II
5.5
20


7.8
88
21
14
20
0.1
8.0

2.3
10
0.3
9.1
0.0
8.6
91

00
11
72
83
40

08

20
19

15
14
8.0
8

15
13
2.9
3.2
1.2


4.7
.o.o..,
10





400

572


334
70

121









158i


.,.....


.0





9.8


10

28
1.0
1.0


5.0
304
43
20
70

4,0
3.0
5.0
1.0
1.8
1.0
2.0
0.5
220
145
10
170
172
113

172

34
44

33
43
2.0

0

1.0
2.5
1.0
1.0
1.0


II

142
7
11.5
10
8
7
I,-I)10
243
82
320

20
8.5
i.. ,
45:
0

8
10
5.5
22
1,440

038
128
1,100
1,000
705

i,070

140
230

121
92
6.5
11
11

7.5
8.5
10
10
11


t1l


13




0.3
.1











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..1.















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.2




......


0.2









.5
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133
127


420
150
220


118
3,000
700
340
800

200
100

160
180

158
140
80
2009
3,100

2,150
430
2,500
2,500
1,720

2,200

440
560

380
340
150

108

150
160
150
150
240


170
120
207


07
722
24(1
1711
250
135
128
'82'
123

138
115
02
205
034
452
190
520
570
444

514

215
210

170
168
108
104

129
136
117
120
200


.. .,











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714
'60
3835
615
141

204
.1,010
1,130
570
1,320
340
274

254
270
244
135
457
4,940

3,370
723
3,940
3,940
2,790

3,7900
742
944

649
578
250
234

251
279
251
256
403


3









7

4


__ I


I


7. 1
7.tl
7.7


7,7
7.4
7.5
7.8
7.8

7.0
7.9
8.2
7.0
7.3
8.0
8.1
7.5
7.0

7.4
7.5
7.7
8.2
7.7

7.0

7.8
7.4

7.8
7.9
8.1


7.8
8.0
7.7
7.8
7.3


. o ,


, ,
..,
. ,
.o..
,,,.
....


o....





.. ,

12
1.
,...,
.. ..
.. ..
... .
. .
1.7
....
,.....

.,o

......
......








TABLE 4. (Continued)

1 2 3 4 6 6 7 8 9 10 11 12 13 14 1 10 17 18 19 20


842-110-2
842-110-3
842-111-4
842-111-8
842-112-1

842-112-1
842-115-3
842-116-1
S 842-116-1.
842-117-1

842-117-8
842-121-1
842-123-1
848-103-1
;. 843-10--4
843-103-4
84-103-4
848-104-1
843-104-4
843-104-81
848-104-12

S 843-106-2
848-106-3
848-106-4
8. 83-106-5


843-110-1
843-111-7
843-116-2
848-118-2
843-120-1

844-104-3
S844-104-4
'844-105-1

844-106-2
844-107-1
S 844-114-4
844-115-8
844-116-1


2- 5-55
3- 1-54
2- 5-55
2- 5-55
3- 1-54

6-23-56
2- 5-55
2-26-54
6-23-56
2-26-54

6-23-56
2-24-54
2-24-54
3- 2-54
2- 2-55

6-25-56
8- 2-54
3- 2-54
2- 2-55
2- 2-55

2- 7-55
3- 2-54
3- 2-54
6-25-56
6-25-56

3- 1-54
2-5-55,
2-23-54
2-23-54
2-24-54

2-24-54
2- 2-55
2- 2-55
3- 2-54
2- 2-55

3- 2-54
4- 9-52
2- 2-55
2-23-54
2- 8-55


0.18







.81.
2.2












.10


94
69
79
96
61



38


34
60
277
271

71
1356
284
138

48
56
36


106
92

33
33


123
69
69
88

40
38

69
58


75
46
57
73
21

11
9.0

8.8
.....s


9.0
17
330
342

7.0
107
360
120

2.4
1.9
.5


97
74
39
8.1
7.1

8.9
92
5.4
2.4
45

.5
2.6
47
45
44


......
......
......
......
......

......
......
. . .
......
......

......
......
......
......
......

......
. . .
. . .
......
......

......
......
......
......
......

......
21
......
......
......


0.03


162


169




178


182
111
135
172
43

14
2.0

1.0
"'i...

14
112
840
1,000

....o..

240
980
288

1.5
1.0
1.0


237
185
90
1.0
1.0

12
200
3
:3
108

4
3.0
138
117
100


1,160
680
840
1,100
252


180
9
12
8.5

10
9.0
100
5,440
5,450

5,400
60
1,750
5,600
1,910

1io
10
10


1,570
1,070
544
18
7

6.5
1,440
38
20
605

8.5
9
820
693
685


0.1


.0


...o.o


.0






















.0


......
......
.
......
......

......
......
......
.....
.

......
.
.
......
,.....

......
..

.....
......

......
0.1
......
..
......


2,600
1,620
1,880
2,450
600

180
170
""166'


150
420
10,500
10,500

3"'80
3,530
10,900
4,100

170
180
120


3,400
2,500
1,280
170
140

140
3,170
300
230
1,620

135
150
1,880
1,580
1,410


54(
36(
431
54(
215

144
132

131
...iii
122
220
2,050
2,080

206
776
2,190
840

130
148
92


664
535
294
116
114

119
685
194
182
405

102
105
440
386
325


5 ... ... .

i......
) ..... .
2 ......


i : :' '
!. ... .




! '. : : '
>. ... .
......
o ,. .









......'


.. .


4,090
2,550
2,960
3,870
1,070

308
290
276
274

274
268
717
16,500
16,600

16,200
561
5,780
17,200
6,520

287
308
205


5,370
3,920
2,010
286
235

239
5,000
804
406
2,540

228
234
2,950
2,480
2,220


7.7 ..
S 7.6 ......
S8.0 ..
S7.7 ..
S7.5 ......

....... 15
7.8 ......
7.6 ......

"7.7' ::..


7.7 ..
7.7
7.4
7.6 ...

...... 14
7.7 ..
7.4 ......
7.8 .
7.8 .. ..

7.9.
7.7 ......
7.9 .


7.4 ....
...... ......

7.8 ....
7.7 ......

7.4 ......
7.7 ......
7.9 ......
7.7 ...
7.9 ....
7.1 ......
7.7 .....

8.1 ..
7.7 ....
7.7.
7.4 ..
7.8 ......


.,.,,,,


.......
......
......
......
......

......
......
. . .
......
......

......
......
......
......
......

......
. . .
. . .
......
......

......
.. .
.. .
......
......

......
2
......
......
......












TABLE 4. (Continuetd)


844-116-1
844-117-8
844-117-8
844-120-1
846-107-1
845-107-3
845-108-3
815-108-3
814-110-1
845-113-1
845-l 13-1
845-113-11
8(6-114-5
845-114-6
545-114-8
845-115-2
845-115-7
846-117-7
845-117-10
845-118-3
845-118-3
845-119-1
845-121-2
845-122-1
846-108-1
846-112-5

846-112-6
846-113-3
846-115-0
846-116-5
846-116-11
846-116-11
846-118-3
846-118-4
846-119-3
846-119-4
846-121-2
846-122-1
846-123-1
847-103-3
847-107-1


2

6-25-56
3- 1-54
8-256-56
2-24-64
3- 2-54
2- 7-5a
2- 7-55

3- 2-54
2- 2-55

6-25-56
1-30-53
1-30-53
1-31-53
2-25-54
2-25-54
3-18-42
8-28-51
2-25-54
6-25-56
11- 5-53
2- 4-55
2-25-54
3-2-54
2-23-54
2- 2-55
2- 7-55
2-25-54
2-25-54
8-28-51

2-6-55
6-25-56
2-25-54
2-25-54
6-25-56

6-25-56
2-25-54
2-25-54
3-2-54
2- 2-55


3













."6
11
8.7



7.0


14







7.0


7




,.,...
.,,,..,


.4 f

0,37 62
45
.40 ...
...... 4f
37
84

4.0
139
114
.. 120
.05 108
.04 70
.07 58
... 55
67
.11 43
.01 50
...... 69
2.8 .......

5.9 88
28
...... 28
46
909
. .. 107
...... 100
9. 9
.. 110
...... 66
0 66

..... 60
1.2 .
...... 61
...... 37


..... 30
...... 37
.... 123
..123


6

48
I 4.6
1...
6.1
1,8

8.7

65.

75
81
71
25
.7
8.8

8.2
8.5
9.0
1.7

7.4
2.9
26
25
54
44
48
12
32
25

30

1.6

..ii...
11
6.6
1.6
58


05
1.0

1,0
2.0
8.0
2.5

205
188

192
188
64
1.5
2.0
6.0
0.5
8.0
1.0

22
2.0
41.0
60
142
130
118
24
90
68

78
4.0
1.0


1.0
1.0
4.0
132


14 15 18 17


_eJ-_l-


11

545
13
13
7
15
25
12

1120=
1250
1,170
408
16
65
118
58
70
9.5

7
6.5
11
405
960

820
725
131
430
345
330
10
7.5
12

8.5
7.0
13
810


12



0.1
.o...,









.. 1
.1







.1

.1












.2


13













0.7
.7
.2



2.0


.1


1,300
170
......
170
148
240
240

2,820

2,850
2,410
950
200
270
430
246
294
222

204
110
260
1,010
2,110
1,880
1,780
560
950
868
800

400
120
.......o

140
90
140
2,040


344
131

140
100

198
228



632
562
278
148
173

218
138
162
180

175
82
221
352
490
430
445
324
298
268

275
156
99


119
67
99
545


......
142
154
182
......


"138'
,.,,,,

,.,...
,. ,
,.....

o.,...
......o


....,.
......

.,,,...
.....,

......
.. ....
18
......,
....o..

..o...
.o....
...,...
......

.,.....
......
.....o
138


632
227
11


37
41
...,

6.4







....93...


219


...,...


132
...... ......
...... ..1... 46
...... 132....


2.100
284
292
285
250

407
416

4,486'
4,440

4,500
4.060
1,620
331
465

721

3668

351
188
435
1,790
3,330

2,950
2,800
943
1,660

1,360

206
263
224
242
150
236
3,200


14
5.6
.6


2.0


. ,


18 19.

7.4
...... 7.8
7.8

7.7
7.0
...... 7.7
8.0

...... 7.4
7.7
7.4
3 7.4
4 7.6
5 7.4
...... 7.5

...... 7.8
10 7.5
25 7.6
...... 7.5
...... ......
9 7.3
8.1
7.4
...... 7.2
7.4

...... 7.7
...... 7.7
...... 7.3
...... 7.8
15 7.7

... 7.7

.... 7.4



7.7
...... 8.6
...... 6.4
...... 7.5


So

12





..
.. ,
.....





12






......


,.....
,... .


......







TABLE 4. (Continued)

1 3 4 5 6 7 10 1 12 13 14 1 16 7 18 1 20


847-107-1
847-108-1
847-108-1
847-110-1
847-110-1
847-112-7
847-113-5
847-113-5
847-113-21
, 847-114-8
847-114-8
847-114-6
847-11-25
847-116-2
847-116-6
847-1611l
847-117-2
847-118-7
847-119-2
847-120-3
847-121-2
847-123-1
848-112-2
848-112-2
848-113-5
848-113-8
848-114-4
848-115-3
848-116-3
848-117-8
848-117-8
848-118-2
848-119-2
844-120-2
848-122-1
849-4105-1
849-117-1
849-117-1
849-118-5


6-25-586
2-2--55
6-25-56
4- 9-52
3-2-54
2-23-54
2-23-54
6-25-56
2-23-54
223-54
6-25-86
8- 2-54
2-25-54
2-23-54
2- 7-55
2-23-54
2- 4-55
4- 9-52
2-25-54
2-25-54
6-25-56
2- 4-55
2-25-54
2-23-54
6-25-56
2- ,-55
6-25-66
2- 7-55
6-14-51
2- 4-55
2-23-84
6-25-56
2-23-64
2-23-54
2-23-54
2-23-54
2- 7-55
2- 4-55
6-25-86
2- 4-55


...... ......

.. .2 .....
...... ......
...... ......
...... ......
...... ......
...... ......
...... ......
...... ......
...... ......
...... ......

11 .11

. ... .
...... ......
...... ......
...... ......
...... .

::::::::::::.




...... ... ...

...... ......


122
326
144
167
107
24
58
84
79
80
77
83
a8
89
65
45
46
42
33

24
22
86

82

113
104
112
101
47
39
a1
27
313
129
43


63
441
80
70
50
29
37
33
17
22
8.3
16
5.1
12
15
10
6.9
3.4
3.9

7.3
9.2
26

36
32
41
50
48
9.0
6.6
2.2
10
310
64
9.0


9.2'


.6
.. .


1"i82
148
...


167


145


10


112
1180
218
220
135,
20
80
90
56
45
90
30
24
29
64
11
4.0
2.0
1.0

1.5
6.0
73

92
98
112
170
171
18
1.0
10
5,0
680
198
'"..'s


5.0





..


1,920
13,900

2,660
2,880

1,880
1,230
1,360.
1,220
714


755 .....
7,450
7,700 0.0
1,390 .0
1,420 ...
880 ...
579 ......
579
570
540
36 ......
260
518 ......
163 ......
94
148 ......
249 .....
47 ......
10 .0
S
7.5
10 .1
6.5 ......
435 ......
10 .1
590 ......
582'" ....
700 .1
820 ....
756 ......


8
0.5 .. .
5,100
1,080 ......
"-S6 ::;;;;


564
2,630
688
678
472
176
296
344
268
290
326
272
166
274
224
154
143
119
09

90
93
320


...... 3,040
.......21,900
20,500
...... 4,950
...... 4,930
...... 3,100
1,940
.......2,140
...... 2,120
..... 1,250
......1,240
2,030
946
... 600
935
...... 1,130
430
...... 324
.... 259
...... 215
...... 281
.... 185
197
...... 1,680
.. .. ,.....


720
.... 1,150
...... 60
359
5580
638
250
.1 188
.. 180
130

...... 110
.... 120
...... 1,050
... 248
...... 1,330
... 'i.1,4106
635
...... 1,900
...... 1,640
272
145
167
.... 123
..... 10,000
...... 2,480
240


2,100
2,220,
2,990
2,690
495,
263
295
232
15,700
3,930
"4'i'


...... 7.3
...... 7.6
2 7.3
...... 7.4
... 7.5
8.4
..... 7.3
7.7
...... 7.7
7.4
.... 7.5
7.7
7.5
7.6
...... 7.6
.... 7.9
2 7.7
.... 8.3
8.1

.... 7.9
..... 8.0
7.6
...... 7.7
... 7.7
5 7.7
7.7
... 7.6

...... 7.7
7.8
7.6
..... 7.8
..... 7.5
7.7
8'.1


12
......









...*..


.4..
.3


355 ......
418
430 300
485 ...
452 ......
154
125 .....
136 ......
109 .
2,060 ......
585
"144.,


I












TABLE 4.


iDOC( ntled)


1 a 3 4 5 6 7 8 U 10 11 s1 13 14 16 l6 17 18 10 20

840-110-3 2-23-54 ...... ...... 4 12 ....... ............ 21 88 ...... .... 320 1 3 .. 34 ...... 7.7
8409- 11-8 2- 4-55 .,., ... 4. 11 .. .. ... .. 1,5 74 ...... .. 280 10 .... 478 ...... 8 0 ......
849-120-2 2- 4-55 ... ...... 57 17 ..... ..... ...... 48 170 ...... ...... 00 212 840 ... 8.0 ......
840-191-2 2-23-54 ...... ...... 44 8.3 ....... ...... ...... 3 0 48 . ... 220 144 3(0 ..... 7.8
840-123-1 2-23-54 ...... ...... 44 14 ............. ....... 4.0 14 ... ...... 13 18 .... 34 ...... 7.7 ......
840-124-6 2-2 4 .... ....... 08 32 ........... ....... 103 20 ......... .. 040 37 ...... 1,30 ...... 7.0

Elder spring ......... 2,8 0.00 8.4 1. 1.8 ...... 1 4.1 ...... 4.8 20 11 ............. 0.4 .
Heath
Spring... 4- 0-52 0.8 .10 .8 1.2 7.0 0.2 6 1.0 12 0.0 .3 40 7 ...... 1 5.0
hanlando
Spriags... 4-23-40 13 .09 29 7.9 5.8 .0 125 3.3 8 .2 ,1 123 105 ...... 228 0 7.2 ..






REPORT OF INVESTIGATIONS No. 27


wells driven into the Pleistocene sand yield water containing an objec-
tionable amount of iron.
CALCIUM
Calcium (Ca) is. dissolved from limestone, shells, and coral, which are
composed largely of calcium carbonate. Calcium imparts the property of
hardness to waters in the county. The concentrations of calcium in 170
ground-water samples ranged from 14 to 326 ppm.
MAGNESIUM
Magnesium (Mg) is dissolved from most rocks but especially from
dolomite and dolomitic limestone, which contain large amounts of mag-
nesium carbonate. As limestones in central Florida contain small amounts
of magnesium carbonate, magnesium is usually found in much smaller
quantities than calcium. Magnesium and calcium are the two major con-
stitutents causing hardness in natural waters.
Magnesium is one of the principal constituents of sea water and it
is found in relatively large quantities in ground water contaminated with
sea water. The magnesium content of 170 ground-water samples from
Seminole County ranged from 0.5 to 441 ppm.

SODIUM AND POTASSIUM
Sodium (Na) and potassium (K) are dissolved from many rocks, but
because sea water is composed mainly of a solution of common salt (so-
dium chloride), large amounts of sodium are usually associated in Florida
with ground water that has been contaminated with sea water or indus-
trial wastes. The sodium content may be 5 to 20 ppm in ordinary ground
water or more than several hundred ppm in a highly mineralized water.
The potassium content is generally relatively small. Waters that contain
only a few ppm of sodium are likely to contain about equal quantities
of potassium. As the amount of these constituents increases, the propor-
tion of potassium becomes less.
The sodium content in 23 ground-water samples in Seminole County
ranged from 4.7 to 730 ppm, and the potassium content in 17 ground-
water samples ranged from 0.2 to'16 ppm (table 4). This table probably
does not show the highest concentrations because the more highly miner-
alized waters were not analyzed for sodium and potassium.
Sodium is not particularly significant in drinking water except for
those persons who require sodium-free diets. A concentration of sodium
greater than 100 ppm may cause foaming in steam boilers. Sodium may
have some effect on the permeability of some soils, particularly clayey
soils.





FLORIDA GEOLOGICAL SURVEY


BICARBONATE
Bicarbonates are common to most waters because of the abundance
of carbonate minerals in nature and because carbon dioxide, which helps
dissolve bicarbonates, is readily available. Bicarbonate, in combination
with calcium and magnesium, causes carbonate hardness.
Ground water from the Floridan aquifer in central Florida usually
contains from 100 to 300 ppm of bicarbonate. The bicarbonate content of
36 ground-water samples from Seminole County ranged from 121 of 334
ppm (table 4).
SULFATE
Sulfate (SO4) is dissolved in large quantities from gypsum (calcium
sulfate) in the rocks and soil. Sulfate is also obtained from salts in sea
water or from oxidation of iron sulfides.
Sulfate has little effect on the general use of water. The U. S.
Public Health Service (1946) recommends that the sulfate concentration
not exceed 250 ppm in drinking and culinary water on carriers subject
to Federal quarantine regulations. Sulfate in hard water contributes to
boiler scale and may have a laxative effect if present in quantities around
300 ppm. The sulfate content of 170 ground-water samples from Seminole
County ranged from 1.0 to 1,180 ppm.
CHLORIDE
Chloride (Cl) is abundant in sea water and is dissolved in small
quantities from rocks. The chloride content of ground water is generally
a reliable index of contamination by sea water because about 91 per-
cent of the dissolved solids content of sea water consists of chloride
salts. The chloride content has little effect on the use of water for ordi-
nary purposes unless it is present in large quantities.
Water from the artesian aquifer beneath most of the hilly upland in
Seminole County has a chloride content of less than 25 ppm, which might
be considered normal for this part of central Florida. Water having a
chloride content above 25 ppm suggests mixing with connate salt
water or salt water that entered the formations during higher stands of
the sea during Pleistocene time.
The chloride content of the 2,062 ground-water samples from the
county ranged from 4 to 7,950 ppm (tables 4, 5, 6). Additional chloride
analyses are shown in table 2 of Florida Geological Survey Information
Circular no. 34.
The U. S. Public Health Service (1946) recommends that the concen-
tration of chlorides not exceed 250 ppm in water on carriers subject
to Federal quarantine regulations. Water has a salty taste when the
chloride content exceeds 500 ppm, and water high in chloride is corrosive







REPORT OF INVESTIGATIONS No. 27


TABLE 5. Chloride Content of Water Samples Collected
at Various Depths in Wells


Date of Chlor- Date of Chlor-. Dateof Chlor-
Well measure- Depth ide con- measure- Depth ide con- measure- Depth ide con-
Number meant (feet) tent -ment (feet) tent ment (feet) tent
(ppm) (ppm) (ppm)

840-107-2 11-28-56 0 1,215 11-28-56 250 1,240 11-28-56 350 1,250
11-28-56 175 1,255 11-28-56 275 1,250 389 1,250
11-28-56 200 1,230 11-28-56 300 1,250
11-28-56 225 1,260 11-28-56 325 1,255
840-120-1 7-19-55 25 9 7-19-55 100 9 7-19-55 170 10
7-19-55 50 10 7-19-55 125 10
7-19-55 75 9 7-19-55 150 10
841-110-12 12- 2-56 0 1,080 12- 2-56 100 1,075 12- 2-56 200 1,025
12- 2-56 60 1,080 12- 2-56 150 1,080 12- 2-56 200 1,030
842-111-6 12- 3-56 0 960 12- 3-56 130 945
12- 3-56 75 960 12- 3-56 189 900
842-111-7 12- 3-56 0 1,300 12- 3-56 140 1,300 12- 3-56 216 1,345
12- 3-56 110 1,270 12- 3-56 180 1,275
845-117-10 7-18-55 5 70 7-18-55 150 76 7-18-55 300 73
7-18-55 50 74 7-18-55 200 73 7-18-55 335 75
7-18-55 100 75 7-18-55 250 74 7-18-55 368 75
846-116-11 7-18-55 15 320 7-18-55 50 335 7-18-55 100 335
7-18-55 30 320 7-18-55 75 330
847-113-31 12- 1-56 100 650 12- 1-56 150 650 12- 1-56 200 660
12- 1-56 125 650 12- 1-56 175 660 12- 1-56 240 675
848-116-12 7-19-55 10 415 7-19-55 175 380 7-19-55 300 380
7-19-55 50 415 7-19-55 200 380 7-19-55 325 380
7-19-55 100 390 7-19-55 225 380 7-19-55 350 380
7-19-55 125 380 7-19-55 250 380 7-19-55 380 380
7-19-55 150 380 7-19-55 275 380 ..... ... ..






66 FLOIDA GEOLOGICAL SURVEY


TABLE 6. Chloride Content of Water That Was Collected
as Wells Were Being Drilled

Date of Chlor- Date of Chlor- Date of Chlor-
Well measure- Depth ide con- measure- Depth ide con- measure- Depth ide con-
Number ment (feet) tent ment (feet) tent ment (feet) tent
(ppm) (ppm) (ppm)

837-103-1 4- 7-56 90 12 4- 7-56 105 17 4- 9-56 130 13
4- 7-56 95 15 4- 7-56 110 16 4- 9-50 145 13
4- 7-56 100 12 4- 9-56 124 14 4- 9-50 154 13
4- 7-56 103 14 4- 9-56 130 14 4- 9-50 158 15
837-103-2 4-27-56 85 26 5- 7-56 142 78 5-30-56 184 80
4-27-56 90 25 5- 7-56 153 80 5-30-56 186 80
4-27-56 94 27 5- 7-56 157 79 5-30-50 190 80
4-27-56 100 26 5- 7-56 157 78 5-30-56 197 85
4-27-56 104 27 5-30-56 146 69 5-30-56 204 80
4-27-56 104 28 5-30-56 148 65 5-30-56 210 80
4-27-56 104 72 5-30-56 151 73 5-31-56 216 73
4-27-56 105 74 5-30-56 153 73 5-31-56 224 75
4-30-56 105 60 5-30-56 155 74 5-31-56 230 78
4-30-56 105 62 5-30-56 150 74 5-31-50 238 80
4-30-56 105 66 5-30-56 160 77 5-31-56 244 78
4-30-56 105 67 5-30-56 164 73 5-31-56 251 83
4-30-56 106 70 5-30-56 167 77 5-31-56 257 84
4-30-56 106 70 5-30-56 170 74 5-31-56 205 83
5- 7-56 108 75 5-30-56 171 77 5-31-56 270 73
5- 7-56 115 78 5-30-56 172 80 5-31-56 272 72
5- 7-56 124 77 5-30-56 177 80 6- 1-50 273 80
5- 7-56 130 77 5-30-56 181 80
841-110-9 12-28-52 106 640 12-31-52 130 645 1- 1-53 150 700
842-111-6 1-12-53 65 450 1-22-53 135 710
1-20-53 80 560 1-27-53 200 755
843-104-13 12- 8-56 60 590 12- 8-56 61 600 12-29-56 62.3 710
12- 8-56 60 600 12-29-56 62 705 12-29-56 02.5 715
12- 8-56 61 600 12-29-56 62.2 700
845-117-8 5- 8-56 159 50 5- 8-56 164 48 5- 9-56 180 49
5- 8-56 160 48 5- 8-56 172 48 5- 9-50 187 51
5- 8-56 161 48 5- 8-56 177 49 5- 9-56 190 49
5- 8-56 163 51 5- 8-56 178 49 5- 9-56 191 47
846-115-15 6-25-56 115 26 6-26-56 145 30 6-26-56 165 90
6-25-56 130 30 6-26-56 155 27 6-26-56 185 31
847-116-8 5-12-52 93 280 5-12-52 120 275 5-13-52 160 280
5-12-52 104 280 5-13-52 100 280
847-116-9 5-19-52 84 290 5-20-52 155 300 5-20-52 200 310
5-19-52 107 295 5-20-52 187 310
847-117-14 11-I-55 84 370 11-17-55 109 480 11-17-55 144 480
11-16-55 90 370 11-17-55 119 480 11-17-55 144 460
II-17-55 91 480 11-17-55 130 480 11-18-55 147 480
11-16-55 92 470 11-17-55 140 470 11-18-55 151 470
11-17-55 100 500 11-17-55 143 470






REPORT OF INVESTIGATIONS No. 27


to boilers and plumbing. A chloride content of more than 800 ppm is
harmful to some irrigated crops (Westgate, 1950, p. 116-123).
FLUORIDE
Fluoride (F) is dissolved from soil and rocks, but the quantity in
natural waters is generally very small. Fluoride concentrations of 34
ground-water samples from Seminole County ranged from 0.0 to 0.4 ppm.
Excess fluoride in water is associated with the dental defect known
as dental fluorosis (mottled enamel) if children drink the water habitu-
ally during the formation of their permanent teeth. Recent studies have
concluded that a fluoride concentration of 0.75 to 1.5 ppm has a bene-
ficial effect on teeth by reduction of the incidence of dental caries
(decay).
NITRATE
Nitrate (NO8) is a relatively unimportant constitutent of most waters
in Florida. Fertilizers may add nitrate directly to water resources. The
presence of high nitrates suggests possible pollution by human and ani-
mal wastes. The nitrate concentration of 20 samples of ground water
from Seminole County did not exceed 5 ppm. This small concentration
has little effect on the use of water for ordinary purposes.

DISSOLVED SOLIDS
The residue of a water, on evaporation, consists of the mineral ma-
terials reported in the analyses. A small quantity of organic material
or water of crystallization is sometimes included. The amount of dis-
solved solids found in 170 ground-water samples from Seminole County
ranged from 80 to 13,900 ppm. Water that has less than 500 ppm of dis-
solved solids is usually satisfactory for domestic use. Water that has more
than 1,000 ppm of dissolved solids is likely to have enough of certain
constituents to produce a noticeable taste or make the water undesira-
ble for many uses.
The dissolved solids content of water was used by Krieger, et al.,
(1957) to classify the degree of salinity of highly mineralized waters.
The divisions used in this publication are as follows:
Description Dissolved solids (ppm)
Slightly saline 1,000 3,000
Moderately saline 3,000 10,000
Very saline 10,000 35,000
Brine 35,000+
According to this classification, ground water in Seminole County can be
classed as fresh (not saline) to very saline.
Figure 81 shows the dissolved-solids content of water from artesian
wells in the county. The dissolved-solids content of the ground water is






FLORIDA GEOLOGICAL SURVEY


less than 500 ppm in all the hilly uplands. This area extends from the
towns of Lake Monroe and Paola south to Orange County, and from
Chuluota and Oviedo west to Orange County. An approximately circular
area around Geneva is included also. Ground water having a dissolved-
solids content of 500 to 1,000 ppm occurs in a relatively narrow band
between the hilly uplands and the level lowlands. Ground water having
a dissolved-solids content of 1,000 to 3,000 ppm occurs in some lands
adjacent to Lake Monroe, Lake Jessup, and the Econlockhatchee River.
The highest concentration of dissolved solids was in ground water ad-
jacent to the St. Johns River, north and east of Geneva. A small area
between Geneva and Oviedo contains ground water also very high in dis-
solved solids.
HARDNESS
The hardness of water is most commonly recognized by high soap
consumption. It is caused by compounds of calcium and magnesium.
These compounds also are active in the formation of scale in steam boilers.
There are two types of hardness in water-carbonate hardness and
noncarbouate hardness. Carbonate hardness is that caused by calcium
and magnesium bicarbonate. Most of this type of hardness can be re-
moved by boiling or by treatment with lime. Noncarbonate hardness is
caused primarily by sulfates, chlorides, and nitrates of calcium and
magnesium and is more difficult to remove.
Water that has a hardness of less than 60 ppm may be rated as soft,
and treatment for removing hardness is justified for few purposes. Hard-
ness between 60 and 120 ppm may be classed as moderately hard, but
does not interfere with the use of water for most purposes. Hardness
between 120 and 200 ppm may be classed as hard and some form of
softening is usually required for many industrial uses. Hardness above
200 ppm may be classed as very hard and is objectionable for most
industrial and domestic uses.
The hardness of 170 ground-water samples from Seminole County
ranged from 62 to 2,630 ppm as CaCO, (table 4). The hardness of water
from the Floridan aquifer in Seminole County is shown in figure 32, which
shows that ground water from the hilly uplands is softer than ground
water from the level lowlands. The water has a hardness between 60 and
120 ppm in a large area between Paola and Longwood, and in smaller
areas west of Altamonte Springs, southwest of Oviedo, east of Chuluota,
and around Geneva. Ground water in the remaining areas of the hilly
uplands has a hardness of 121 to 200 ppm. Ground water having a hard-
ness of over 200 ppm occurs in most of the area adjacent to the St. Johns,
Econlockhatchee, and Wekiva rivers and in the areas adjacent to Lake
Jessup, Lake Monroe, and Lake Harney. The hardness of ground water







REPORT OF INVESTIGATIONS No. 27


exceeds 500 ppm in an area surrounding both sides of the northern half
of Lake Jessup, and encircling the 4- to 6-mile area of lower hardness that
surrounds Geneva. This area extends southward along the St. Johns
River into Orange County.
HYDROGEN SULFIDE
Hydrogen sulfide (H2S) is found in most artesian water in Seminole
County. This gas has a very distinct taste and odor which has caused
the water to be called sulfur water. Hydrogen sulfide in ground waters
is probably caused by the bacterial reduction of sulfates, by water cir-
culating through iron sulfide, and resulting from organic matter. It may
usually be removed by aeration or by allowing the water to stand in an
open container.
The amount of hydrogen sulfide in 15 samples of ground water ranged
from 0.6 to 24 ppm (table 4). A strong odor is imparted by less than 1
ppm of H2S in water. The amount of hydrogen sulfide differs consider-
ably within Seminole County.
HYDROGEN-ION CONCENTRATION
The hydrogen-ion concentration of a water is a measure of the degree
of acidity or alkalinity. This concentration is reported as pH. A pH of 7.0
represents neutrality, which means that the water is neither acid nor alka-
line. A pH higher than 7.0 indicates increasing alkalinity and a pH lower
than 7.0 indicates increasing acidity.
Most ground waters from the Floridan aquifer are slightly alkaline
and the pH usually ranges from 7.0 to 8.0. In Seminole County, the pH
of 163 artesian water samples ranged from 7.2 to 8.5 (table 4). The pH
of water from shallow wells driven in the Pleistocene sands are usually in
the acidic range from about 5.0 to 7.0. Water with a pH of less than
7.0 is likely to be more corrosive than water with a pH higher than 7.0.
CHEMICAL CHARACTER OF GROUND WATER
Figure 33 shows bar graphs of the 3 principal cations and 3 principal
anions, in equivalents per million (epm) in water from 20 artesian
wells and 3 springs in Seminole County. The water of low dissolved-
solids content is of calcium bicarbonate type; as the dissolved-solids con-
tent increases, the water becomes of sodium chloride type. The sum of
the cations and anions in artesian well water ranged from 2.29 to
46.50 epm. This upper range is not the maximum limit because the most
highly mineralized water was not sampled. The analyses of water from
two springs that obtain their water from Pleistocene sand showed that
they contained 0.45 and 0.66 epm, which is a very small amount of
dissolved minerals. The water from the only artesian spring sampled
contained 2.36 epm and is of calcium bicarbonate type.






FLORIDA GEOLOGICAL SURVEY


V i __ __'" ._
6I X


S------- --- x---










Figure 3.3. Bar graphs of the chemical analyses of water from 20 artesian wells










30 times from well 845-114-6, near the recharge area, to well 845-114-5,

and more than 80 times from well 845-114-6 to well 845-118-11. The sum
Fi Bar graphs of the sodium and potassium ions increased of water from 20 artesian wells
and 3 springs.









Calcium increase the in chemical con in well 845-114-, neased disthe recharge
the re and there is not enough magnesium to plot; the magnesium chloride
content increases most. The concentration of chloride increased almost


30 times from well 845-114-5 is more than one-harg the area, to well 845-114-5,
and more thagnesium exceed 80 times calcium well 8451146 to well 845-113--11. Most of the calcium
of the sodium and potassium ions increased from 0.5 to 28 epm.
Calcium is the principal cation in well 845-114-6, near the recharge
area, and there is not enough magnesium to plot;' the magnesium con-
tent in well 845-114-5 is more than one-half the calcium content; and
the magnesium exceeds calcium in well 845-113-11. Most of the calcium
is probably dissolved from the limestone formations and most of the
magnesium probably comes from sea water that has not yet been flushed
from the aquifer. (See the following section.) The sulfate content in-
creased only slightly as compared to the above constituents. Bicarbonate
is the only principal ion that decreased away from the recharge area.







REPORT OF INVESTIGATIONS No. 27


2 tMINULt L.UUUNITY
- 25 Map showing approximate location of wells
EXPLANATION

Sod"m and ChR. W Xd
SPo.o11um
Mognium Sulfol

10 Ca lslum Bicarbonat
o1 X




0 025 0.50 0.75 1.00 1.25 1.50
DISTANCE, IN MILES FROM APPROXIMATE CENTER OF RECHARGE AREA
Figure 84. The relationship of the chemical constituents in ground water to the
distance of the wells from a recharge area centered near Golden and Silver lakes.


SALT-WATER CONTAMINATION
Salty water is present in the Floridan aquifer in many parts of Florida.
Although salty water could result from several causes, in Seminole County
it appears to be the result of the infiltration of sea water into the
aquifer during the Pleistocene time, when the sea stood higher than at
present. Since the last decline of sea level, fresh water entering the
aquifer has been slowly diluting and flushing out the salty water. Water
samples collected from wells of different depths in the northern
and central parts of the county show that flushing has progressed further
in the upper part of the artesian aquifer than in the lower part. One of
the most serious water problems facing the county is the danger that
withdrawals from the upper part of the aquifer will cause water from
the lower zones to move upward and contaminate the water in the upper
part of the aquifer.
The last extensive stand of the sea over Florida was the Pamlico
sea, which occurred during the mid-Wisconsin Glacial Stage of the





FLORIDA GEOLOGICAL SURVEY


Pleistocene Epoch. This sea stood approximately 25 feet above present
sea level and inundated about half of Seminole County (fig. 35).
Figure 35 is a map of Seminole County showing the relationship of the
Pamlico shoreline (at 30 feet above sea level) and the 250 ppm isoch-
lor. (An isochlor is defined as a line on a map connecting points at which
the chloride content of ground water is equal.) This figure shows a
definite relationship between the 250 ppm concentration of chloride in
the artesian water and an altitude of 30 feet above sea level. Almost all
the wells that yield water having a high chloride content are in areas -
where the land surface is less than 30 feet above sea level.
Analyses of samples from more than 700 wells show that the chloride
content from the upper part of the Floridan aquifer ranges from 4 to
7,950 ppm. Several samples of water having a chloride content of 4.0
ppm were collected from wells near Paola, southwest of Lake Jessup, and
in the area southeast of Lake Mary. The water having the highest
chloride content was collected from a well at Mullet Lake Park, near
the St. Johns River. The general results of these analyses are shown in
figure 36. As may be seen from the figure, water from the Floridan
aquifer beneath most of the hilly upland has a chloride content of less
than 25 ppm. The relatively low chloride content of the artesian water
in the hilly upland is probably due to the fact that this is a recharge
area for the Floridan aquifer. Another reason for the low chloride con-
tent of the artesian water in this area may be that the last inundations
from the ocean covered only the land at a lower altitude.
The low chloride content of artesian water in local recharge areas was
first noted by Stringfield (1936,.pl. 16) in his investigation of the artes-
ian water in the Florida Peninsula. After making subsequent investiga-
tions in Seminole County and mapping the chloride content of the
artesian water in the county (V. T. Stringfield, unpublished map in files
of U. S. Geological Survey), he concluded that the low chloride content
in the Geneva area was a result of flushing by local recharge (R. C.
Heath, oral communication).
The areas in which the artesian water contains more than 25 ppm
chloride include the northeastern half of the county (except for the hilly
upland around Geneva) and a narrow belt along the valleys of the
Wekiva and Little Wekiva rivers (fig. 36).
Water that has a chloride content ranging from 26 to 250 ppm is
suitable for drinking, irrigation, and most industrial uses. A chloride con-
tent of more than 250 ppm exceeds the amount generally recommended
for a municipal water supply. Areas in which the chloride content of
ground water exceeds this limit include: a thin band from the Wekiva






REPORT OF INVESTIGATIONS No. 27


River eastward to the St. John's River, the area adjacent to Lake Monroe
on both sides of Sanford and extending around the north side of Lake
Jessup, a small area 2 miles south of Sanford, a thin band circling Geneva
and extending along part of the Econlockhatchee River, and an area
northeast of Oviedo (fig. 86).
Ground water that has a chloride content ranging from 1,000 to 5,000
ppm is unsuitable for drinking, many industrial uses, and for the irriga-
tion of most crops (Westgate, 1950, p. 116-128). Areas in which such
ground water occurs include land adjacent to the Wekiva and St. Johns
rivers in the northwest corner of the county, a very small area 2 miles
northwest of Sanford, most of the land adjacent to the northwestern part
of Lake Jessup, a semicircular area north of Geneva, and an area south-
east of Geneva (fig. 86).
Water containing more than 5,000 ppm of chloride is almost unus-
able for any purpose. Such ground water is obtained from a small area
extending from Mullet Lake northeast along the St. Johns River, and an
area south of Lake Hamey (fig. 36).
Chemical analyses of water samples collected periodically, coinci-
dent with measurements of artesian pressure, indicate that the chloride
content of the artesian water may vary with changes in artesian pressure.
Figure 87 illustrates changes in the chloride content and the water level
of three wells south of Sanford. This figure includes data collected by
Stringfield, 1986, Stubbs, 1987, and Irving Feinberg in 1939 (personal
communication) as well as data collected during the present investiga-
tion. The graphs for well 845-113-1, 4.8 miles southeast of Sanford, illus-
trate the effect of water-level changes in the chloride content of the
water from 1953 through 1956. The chloride content was lowest when
the water level was highest during the latter part of 1953. After this
date the water level declined as a result of decreased rainfall and the
chloride content increased. The chloride content increased approximately
250 ppm during the period of record. In order to show what effect the
period of flow prior to collecting the water sample had on the chloride
content of the water, symbols were used in figure 37 to show different
periods of flow. The period of flow apparently had little effect on the
chloride content of the water from well 845-113-1.
The graphs for well 844-116-1, 5.8 miles south of Sanford, indicate no
relation of the chloride content of the water to changes in the water level.
The graphs show a decrease of about 100 ppm of the chloride content
during the 20-year period of record, with decline of water level of ap-
proximately 1 foot during normal rainfall years.
The graphs for well 844-114-1, 4.4 miles south-southeast of Sanford,








74 FLORIDA GEOLOGICAL SBVEY




,30 ---



f i,- CHLORIDE CONTENT
Well 845-113-1. 4. miles southeast of Sonfrd
29

218-

28 /
27

^ 26

25


WATER LEVEL
23


1 _CHLORIDE CONTENT
w 600

3 500 Well 844-116-1, 53 miles south of Sanford


j 36

35 ---
:. V- -- -

z 34

4 3z
32

< 31
WATER LEVEL
30

800
S S goo, --- --- --- --- --- ---
j- 7* 5n flowing for indefltIe p.
z Will flowing for live minute
0 700-

bg600
SCHLORIDE CONTENDT
U. 50 Well 844-114-1, 4.4 miles south-southeost of S
3J

p -> 30

.3 29
28

p- 27
27 ----- E LE

26-- -
WATER LEVEL
25 152-1 553


Figure 37. Hydrographs and chloride content of water from wells 844-114-1,
844-116-1, and 845-113-1.






REPORT OF INVESTIGATIONS No. 27


show some correlation of the chloride content of the water to changes in
the water level. The chloride content increased about 150 ppm from 1937
to 1954 with a corresponding decline in the water level of about 1 to
1I feet. An indefinite period of flow prior to sampling seems to give a
slightly higher chloride content than a 5-minute period of flow.
Graphs of water level and chloride content of the water in three wells
west of Sanford are shown in figure 38. Well 849-119-3, 0.4 mile west of
Lake Monroe, shows that the chloride content varied considerably during
the period of record. This change in the chloride content bears some
relation to the change in the water level, but the most important factor
seems to be the period of flow prior to sampling. Since 1951 the chloride
content had been less than 79 ppm when the well was sampled after
flowing only 5 minutes. When the well was sampled after flowing long-
er than 5 minutes, the chloride content of the water ranged from 65 to
290 ppm. This amount of fluctuation would tend to mask any progres-
sive trend in the chloride content. During the dry period of May 1939,
the chloride content of the water was almost 250 ppm. The change in
water level from 1937 and 1939 to 1956 seems to indicate a decline of
about 1 foot during the period of record.
The graph for well 848-117-8, 1.9 miles west of Sanford, shows close
correlation of the chloride content of the water to changes in the water
level. The chloride increased about 150 ppm from 1937 to 1954 with a
corresponding decline in the water level of about 19 feet. In addition,
many of the high water levels during the years 1952-56 correspond to
low chlorides.
The graph for well 848-116-2, 0.4 mile west of Sanford, shows very
little correlation of changes in the water level with changes in the
chloride content. The vertical permeability must be relatively low near
this well. The water level declined 6 feet from 1953 to 1956 and the
chloride content did not change any significant amount.
Figure 39 shows the graphs of the chloride content and water level
for two wells about 2.5 miles northeast of Oviedo. Although the wells
are only 600 feet apart, they show considerable differences in both the
water level and the chloride content. Well 841-110-12 is 213 feet deep
and is cased to 58 feet. Well 841-110-9 is 156 feet deep and is cased to
53 feet. In January 1953 the level in the deeper well was about 8
feet above that in the other well. The chloride content in the deeper
well was about 370 ppm higher than in the other well. In December
1956, the water level in the deeper well was only about 2 feet above
the water level in the other well, and the chloride content was only 185
ppm higher than that of the other well. The fact that both the water







FLORIDA GEOLOGICAL SURVEY


zp700
Wl flowing for indefinite period
2 6 Well flowing for five minute.-


I CHLORIDE CONTENT
U Well1 848-116-2 0.4 mile west of Sonford-<

24



Eta
uJ

i VL
WATER LEVEL
1 1935 1937 1939 1951 1952 1953 1954 1955 1956

Figure 38. Hydrographs and chloride content of water from wells 848-116-2,
848-117-8, and 849-119-3.






REPORT OF INVESTIGATIONS No. 27


IZ
to 1)00k
zQ goo



da..



0:Li
j 900
U-
W
U_ F
zi 24[




OW W


I


70 CHLORIDE CONTENT OF WATER
SWELL 841-110-9, 2.5 MILES NORTHEAST OF OVIEDO

j o WATER LEVEL


SA A
0 V


1953 1954 1955 1956


Figure 39. Hydrographs and chloride content of water from wells 841-110-9 and
841-110-12.

level and the chloride content of water from these two wells are ap-
proaching each other indicates the upper and lower water may be mix-
ing. The usually effective confining bed may be penetrated by the bore
hole of the deeper well. The water level in well 841-110-12 fluctuated
through a range of 12 feet-the largest fluctuation measured in Seminole
County during the investigation.
Graphs shown in figure 40 illustrate the chloride content of the water
and the water level for two more wells in Seminole County. Well 846-
112-5 is 4.2 miles southeast of Sanford and well 842-112-1 is 2.3 miles
north of Oviedo. In general, figure 40 shows the significant changes that
are seen on most graphs for wells in the two areas. Near Sanford, the
water levels have remained about the same or declined slightly since
1939. The decline in water levels is probably due to an increase in


WW
Q a.

I-,-

LLI
W
zz
Uw-
LW -
00
~ OLc






FLORbA GEOLOGICAL SUVwEY


Figure 40. Hydrographs and chloride content of water from wells 84212-1 and
846-112-5.
pumping in the area. The chloride content of the water shows more
fluctuation in the Sanford area than around Oviedo. This can probably
be attributed to an effective confining layer of dense limestone in the
Oviedo area that retards the upward movement of salty water from
below.
The hydrographs for wells around Oviedo indicate a decline in the
water level of about 2 to 8 feet since 1939. This decline can be attributed
to the increased use of water in the area near Oviedo.
Figure 41 presents data from four wells in the county. These data
include information on the water level, chloride content of the water,
temperature of the water, and yield of the well. In general, the graphs
for these four wells show a very close relationship of the changes in
water level and changes in yield of the well (subject to slight errors
of measurement), but little change in temperature of the water, and
little correlation of changes in the water level with changes in the



















































Figure 41. Data from wells 842-110-2, 843-108-4, 845-113-10, and 848-113-1.


PRfotjoT oF INVESTIGATIONS No. 27






FLORIDA GEOLOGICAL SURVEY


chloride content of the water. The temperature of water from these flow-
ing wells is almost constant during the year.
The data for the graphs plotted in figure 42 were collected in 1933
by V. T. Stringfield, in 1937 by S. A. Stubbs, and in 1939 by Irving
Feinberg, and during the present investigation. The data are again used
to compare measurements made in the past to those made more recently
in order to observe any trends. The graphs for these three wells show
information similar to the data given in figure 41.
The graphs for well 849-117-1, 1.7 miles northwest of Sanford, show
little correlation between the changes in chloride content to changes in
the water level. The chloride content increases about 100 ppm after
the water flows for a long period which suggests that salty water may
be moving up from deeper formations. An inspection of the water-
temperature graph indicates an annual fluctuation of about 3F. How-
ever, the variation reflects soil temperature because the well outlet is
offset and the water travels through a horizontal pipe located about 1
foot below the surface. The water level in well 841-111-1, 1.8 miles north-
east of Oviedo, has fluctuated as much as 15 feet during 1937-56 and as
much as 11 feet during December 1953 to February 1954. The chloride
content has remained almost constant during 1937-56. The water level
in well 841-110-1, 2.6 miles northeast of Oviedo, has declined about 3
feet during 1951-56 while the chloride content has increased slightly
during the period.
QUANTITATIVE STUDIES
The principal hydraulic properties of an aquifer are its capacities to
transmit and store water, for all aquifers serve as both reservoirs and
conduits. The Floridan artesian aquifer acts primarily as a conduit, trans-
mitting water from recharge areas toward discharge areas; however,
some of the water is yielded by compression of the aquifer material and
the water.
The coefficient of transmissibility is a measure of the ability of an
aquifer to transmit water. It is the quantity of water, in gallons per day,
that will flow through a vertical section of the aquifer 1 foot wide and
extending the full saturated height of the aquifer, under a unit hydraulic
gradient, at the prevailing temperature of the water. The coefficient of
storage is a measure of the capacity of an aquifer to store water, and is
defined as the volume of water released from or taken into storage per
unit surface area of the aquifer per unit change in head normal to that
surface.
The withdrawal of water from an aquifer creates a depression of the
water level in the vicinity of the point of withdrawal. This depression








REPORT OF INVESTIGATIONS No. 27


Figure 42. Data from wells 841-110-1, 841-111-1, and 849-117-1.


119

13
,Joo

S1,000

24
d
I. 23
I' 22






S00


0 10
hi





U 18
2uj 204





32

4U)



W2
^S 16





OUL 90c





A 33



31C
I-

W Z




0




































Figure 43. Flow-measuring apparatus (a, well valve with 4-inch discharge pipe; b,
4-inch dresser coupling; c, 9-inch fitting to measure; d, quick-closing
valve; e, 4-inch pipe, 4 feet long; f, l-inch piezometer tube; g, 4-inch
by 2U-inch orifice; h, staff gage and tube to measure artesian pressure).






REPORT OF INVESTIGATIONS No. 27


has the approximate form of an inverted cone and is referred to as the
cone of depression. The distance the water level is lowered at any given
point within this cone is known as the drawdown at that point. The size,
shape, and rate of growth of the cone of depression depend on several
factors, including (1) the rate of pumping, (2) the transmissibility and
storage capacities of the aquifer, (3) the increase in recharge resulting
from the lowering of the water level, and (4) the decrease in natural
discharge due to the lowering of the water level.
A portable apparatus was constructed to measure the discharge of
flowing wells and is shown in figure 43. This apparatus consisted of a
4-foot length of 4-inch diameter pipe, threaded at both ends, having a
calibrated orifice fitting at one end of the pipe. The other end of the
pipe was attached to a 3-inch valve by a 4-inch reducing coupling and
a 3-inch nipple. "Dresser" couplings in 2-, 3-, and 4-inch sizes, together
with appropriate pipe fittings, were used to connect the equipment to
the discharge pipe of a flowing well.
In order to cover different ranges of flow two calibrated orifices were
made from a 4-inch pipe coupling that was cut in half, and a plate of
stainless steel was welded to each of the two pieces. A sharp-edge orifice
opening was machined from the plates to exact diameters of 2D and
3 inches. The 22-inch orifice was used to measure flows ranging from
50 to 180 gpm and the 3-inch orifice was used to measure flows ranging
from 100 to 300 gpm.
In order to open or close the flow rapidly a gate valve was machined
and changed to a quick-closing valve operated by a lever. A %-inch hole
was tapped in the center of the pipe, 2 feet from the orifice, and a
piezometer tube consisting of a 5-foot length of clear plastic hose was
connected to the hole. Another l-inch hole was tapped in the nipple
used between the valve and dresser coupling, to measure the artesian
pressure in the well when the valve was closed. A long piece of clear
plastic hose was connected to this opening.
The results of eight recovery tests made by using this portable appa-
ratus are shown on table 7. The table shows that the coefficients of
transmissibility differ considerably throughout the county. The average
of the coefficients of transmissibility determined from the 8 tests was
164,000 gpd per foot. If the transmissibility determined from the test
at well 841-110-9 is not used, the average coefficient of transmissibility
is 185,000 gpd per foot. Well 841-110-9 penetrates only a few feet of the
aquifer, which accounts for the very low coefficient of transmissibility.
A sample plot of the recovery data for well 841-113-8 is shown in






FLORIDA GEOLOGICAL SURVEY


TAaBL 7. Data From Recovery Tests of Artesian Wells in Seminole County
Transmis- Specific
sibility- Yield of Diameter Time of capacity
Well (gpd per well of well test (gpm per
number foot) (gpm) (inches) (minutes) foot) T/Sp.C.
838-114-8 253,000 96 4 60 22 12,000
841-110-9 9,100 40 4 60 8 1,100
841-113-3 98,000 26 2 90 3 33,000
842-110-7 223,000 50 3 90 8 29,000
843-118-4 315,000 68 3 120 13 24,000.
845-113-1 82,000 68 3 75 8 11,000
847-112-7 193,000 44 2 20 4 47,000
849-118-5 134,000 71 4 40 12 11,000


figure 44. The formula used to determine the coefficient of transmissibil-
ity was the time-drawdown method of Cooper and Jacob (1946, p. 526-
264 Q
535), stated as T = where:
aS
T=coefficient of transmissibility in gpd per foot
Q=yield in gpm
AS--difference in drawdown (or recovery) over one logarithmic cycle


A short aquifer test was made in August 1955 of well 845-113-15.
The well was allowed to flow at 60 gpm for a period of 18 hours.
Measurements of the artesian pressure were made periodically on well
845-113-16,25 feet from the flowing well during the test.
The observed data for well 845-113-15 were analyzed by the Theis






-










a l .A O a go ) to AM SPMoo MW so 0MO
1MU, I P MO ePt..
Figure 44. Semilog plot of recovery versus time in well 841-113-3.






REPORT OF INVESTIGATIONS No. 27


graphical method, as described by Wenzel (1942, p. 87-89). This method
involves the following formula, which relates the drawdowns in the
vicinity of a discharging well to the rate and duration of discharge:
0o
114.6Q e-u du 114.6Q W(u)
s \-- du= W(u)
T u T

u
-U

where u = 1.87rS
where u
Tt
s = drawdown, in feet, at distance r and time t
r = distance, in feet, from pumped well
Q = pumping rate, in gpm
t = time since pumping began, in days
T = coefficient of transmissibility, in gpd per foot
S = coefficient of storage, a dimensionless ratio
The formula is based on certain assumptions, which include the
assumptions that the aquifer is of uniform thickness, of infinite area
extent, and is homogeneous and isotropic (transmits water with equal
ease in all directions). It is assumed also that there is no recharge to
the formation or discharge other than that from the one well within
the area of influence of the well, and that water may enter the well
throughout the full thickness of the aquifer.
114.6 Q
Inserting the values in the formulas T= 1 6 W(u) and S =
uTt
7 gives a transmissibility of 51,000 gpd per foot and a storage
1.87r2
coefficient of 0.000004. Data collected and analyzed from well 845-113-1
(table 7), located 150 feet away from well 845-113-15, show a value of
82,000 gpd per foot for the transmissibility. This value was calculated
using the time-drawdown method. These values do not represent the
transmissibility of the entire artesian aquifer as they are drilled only a
relatively short distance into the artesian aquifer. Deeper wells would
draw from a greater thickness of the aquifer and would, consequently,
show higher values.
Values of coefficients of storage for artesian conditions in other areas
range from about 10-4 to about 10-3. The value of 4 x 10-6 obtained in
this test is very small. However, Jacob and others (1940, p. 44) state
that when the ratio of the lateral distance between the observation well
and the pumped well to the depth of aquifer is small, the value of the
computed, storage coefficient is likewise small. Also, it is known that
the values of storage coefficient obtained during short periods of pumping
are comparatively small and that: during prolonged pumping the






FLORIDA GEOLOGICAL SURVEY


computed storage coefficient increases in value. Both of the above condi-
tions applied at the test site and a higher value of the storage coefficient
for artesian conditions is believed to apply in Seminole County.
The selected average coefficient of transmissibility of the upper part
of the Floridan aquifer in Seminole County is about 185,000 gpd per foot
and an assumed value for the storage coefficient is about 0.0005 (a
value halfway between 10-4 and 10-3 in the preceding paragraph).
As the coefficients of transmissibility and storage may differ considerably
from place to place, it is not practicable to predict drawdowns in one
place on the basis of information collected in another place. However,
in order to illustrate how water levels are affected in the vicinity of a
pumped well, figure 45 was constructed. The figure shows theoretical
TIME, IN SECONDS
10 50 100 500 tPQOO I5,00 10 l



'a1
I--

SI log cycle
>-1 As=O.07 ____________ _____ __________ ____
19Ss= 0.07 ..---"




0.07
7 T= 98,000 gpd /ft

I 1 1 I 1 1
Figure 45. Theoretical drawdowns in the vicinity of a well being pumped at a rate
of 1,000 gpm for selected periods of time.

drawdowns in the vicinity of a well pumping at a rate of 1,000 gpm
from an aquifer having a coefficient of transmissibility of 185,000 gpd
per foot and a storage coefficient of 0.0005.
As the drawdowns outside the pumped well vary directly with the
discharge, drawdowns for greater or lesser rates of discharge can be
computed from these curves. For example, under the assumed conditions
the drawdown 100 feet from a well discharging at 1,000 gpm would
be 8.6 feet after 100 days of discharge. If the well had discharged at
100 gpm for the same length of time, the drawdown at the same distance
would have been only one-tenth as much, or 0.86 feet.






REPORT OF INVESTIGATIONS No. 27


SUMMARY AND CONCLUSIONS
The principal source of ground water in Seminole County is the
Floridan aquifer, which is a thick section of limestone that underlies
the entire county. The upper surface of this aquifer ranges from 75 to
about 150 feet below the land surface. The limestone is overlain by
deposits of clay which-differ in thickness, from place to place. The clay
is relatively impermeable and partially confines the water in the lime-
stone. A deposit of sand, 10 to 75 feet thick, overlies the clay. Small
supplies of water are obtained in almost all parts of the county from
screened wells that penetrate only the deposits of sand.
Most of the ground water in Seminole county is probably derived
from rain that falls on the recharge areas in Polk and Orange counties,
although some is derived from rainfall in Seminole County. The areas
of recharge in Seminole County are near the towns of Lake Mary,
Geneva, Chuluota, Oviedo, Altamonte Springs, and Paola.
Natural discharge of ground water in Seminole County is through
large artesian springs such as that at Sanlando, and through springs
and seeps in the bottom of Lake Jessup, and the St. Johns and Wekiva
rivers.
Records of the seasonal fluctuations of artesian pressure show that
the piezometric surface is lowered as much as 12 feet in the Oviedo area
during the periods of heaviest withdrawal. The maximum seasonal
fluctuation in the Sanford area is about 7 feet, and the minimum seasonal
fluctuation is about 5 feet.
Water-level measurements made in the 1930's, by Stringfield, Stubbs,
and Feinberg were compared with measurements made during the pres-
ent investigation-to determine long-term changes of water level. When
similar rainfall periods are compared, the long-term trends of the water
level usually reflect changes in pumpage other than variations in rainfall.
In the area around Sanford, the average long-term decline of the water
level in 14 wells was slightly greater than 1 foot. The trend of the water
levels in these 14 wells ranged from a rise of about 1 foot in one well to
a decline of about 4 feet in another.
The average long-term decline of the water level in five wells near
Oviedo was about 338 feet. The water level in one well did not show
any decline but in another well it showed a decline of about 8 feet.
T...-he water level in a well at Wagner rose about 1 foot during the period
of record, while in a well at Slavia it declined about 3 feet. The decline
of water level in Seminole County was probably caused by an increase
in the use of water in several areas. The seasonal fluctuations of water
level are much greater than the long-term fluctuations.





FLORIDA GEOLOGICAL SURVEY


Stubbs (1937, p. 33) stated that the minimum permanent loss of
head within the flowing-well area ranged from 4 to 10 feet during the
period 1912-37.
The chloride content of water from artesian wells in Seminole County
ranges from 4.0 ppm near the recharge areas to more than 7,500 ppm
near Mullet Lake. In most of the Sanford-Oviedo farming area, the
chloride content ranges from about 10 ppm to slightly more than 1,500
ppm. The seasonal variation of the chloride content in the farming areas
near Sanford was only 35 ppm in one well and as much as 265 ppm in
another well. The seasonal change in the chloride content of water
from wells near Oviedo is only 16 ppm in one well and as much as
180 ppm in another well. Analyses of water samples from wells of dif-
ferent depths show that the chloride content increases with depth in
many areas.
Comparisons of chloride analyses made in the 1930's, by Stringfield,
Stubbs, and Feinberg, with analyses made during the present investi-
gation were used to determine the long-term trend of the chloride
content. In the Sanford area, the average long-term increase in the
chloride content of water from eight wells was about 30 ppm;
the water from three of these wells showed an increase of about 150 ppm,
the water from three other wells did not show any appreciable change,
and the water from two wells indicated a decrease of about 100 ppm.
The water from three wells near Oviedo did not show any appreciable
change in chloride content during the period of record.
The data collected on chemical quality of water show that the ground
water ranges from excellent in some parts of the county to unusable for
most purposes in other parts of the county. The most highly mineralized
water comes from the lowland areas of the county. The chloride content
of the water generally serves as a good indication of the dissolved-solids
content of the water.
Field determinations of the coefficient of transmissibility ranged from
9,100 to 315,000 gpd per foot; however, the lowest value was determined
at a well that penetrates only a few feet of the aquifer. The average
transmissibility coefficient determined from seven recovery tests was
185,000 gpd per foot. The transmissibility and storage coefficients deter-
mined by an aquifer test made of well 845-118-15 were 51,000 gpd per
foot and 0.000004, respectively. However, the true value for the storage
coefficient in the upper part of the Floridan aquifer in Seminole County
is believed to be about 0.0005. The tests show that the coefficients differ
considerably throughout the county.







REPORT OF INVESTIGATIONS No. 27


REFERENCES
Applin, E. R. (see Applin, P. L.)
Applin, P. L..
1944 (and Applin, E. R.) Regional subsurface stratigraphy and structure of
Florida and southern Georgia: Am. Assoc. Petroleum Geologists Bull.,
v. 28, no. 12, p. 1673-1753:
1951 Preliminary report on buried pre-Mesozoic rocks in Florida and adjacent
states: U. S. Geol. Survey Circ. 91, 28 p.
Barraclough, J. T. (see Heath, R. C.)
Bishop, E. W.
1956 Geology and ground-water resources of Highlands County, Florida:
Florida Geol. Survey Rept. Inv. 15.
Black, A. P.
1951 (and Brown, Eugene) Chemical character of Florida's waters-1951:
Florida State Board Cons., Div. Water Survey and Research Paper 6.
Brown, Eugene (see Black, A. P.)
Clapp, F. G; (see Matson G. C.)
Collins, W. D.
1928 (and Howard, C. S.) Chemical character of waters of Florida: U. S.
Geol. Survey Water-Supply Paper 596-G.
Cooke, C. W.
1926 Geology of Alabama; the Cenozoic formations: Alabama Geol. Survey
Spec. Rept. 14, p. 251-297, 5 pts.
1945 Geology of Florida: Florida Geol. Survey Bull. 29.
Cooke, C. W.
1929 (and Mossom, Stuart) Geology of Florida: Florida Geol. Survey 20th
Ann. Rept., p. 29-227, 29 pls.
Cooper, H. H., Jr. (see also Jacob, C. E.)
1946 (and Jacob, C. E.) A generalized graphical method for evaluating for-
mation constants and summarizing well-field history: Am. Geophys.
Union Trans., v. 27, no. 4.
Dall, W. H.
1887 Notes on the geology of Florida: Am. Jour. Sci., ser. 3, v. 34, p. 161-170.
1892 (and Harris, G. D.) The Neocene of North America: U. S. Geol. Survey
Bull. 84, 349 p., 8 pls.
Ferguson, G. E. (see also Parker, G. G.)
1947 (and Lingham, C. W., Love, S. K., and Vernon, R. O.) Springs of
Florida: Florida Geol. Survey Bull. 31.
Gunter, Herman (see Sellards, E. H.).
Harris, G. D. (see Dall, W. H.)
Hatchett, J. L. (see Krieger, R. A.)
Heath, R. C.
1954 (and Barraclough, J. T.) Interim report on the ground-water resources
of Seminole County, Florida: Florida Geol. Survey Inf. Circ. 5.
Heilprin, Angelo
1887 Explorations on the west coast of Florida and in the Okeechobee wilder-
ness: Wagner Free Inst. Sci. Trans., v. 1, 134 p.
Howard, C. S. (see Collins, W. D.)






FLORIDA GEOLOGICAL SURVEY


Jacob, C. E. (see also Cooper, H. H., Jr.)
1940 (and Cooper, H. H., Jr.) Report on the ground-water resources of the
Pensacola area, Escambia County, Florida, with a section on the geology
by S. A. Stubbs: U. S. Geol. Survey open-file report.
Krieger, R. A.
1957 (and Hatchett, J. L., and Poole, J. L.) Preliminary survey of the saline-
water resources of the United States: U. S. Geol. Survey Water-Supply
Paper 1374, 172 p. 2 pls., 3 figs.
Leutze, W. P. (see Wyrick, G. G.)
Lingham, C. W. (see Ferguson, G. E.)
Love, S- K. (see Ferguson, G. E.; Parker, G. G.)
Matson, G. C.
1909 (and Clapp, F. G.) A preliminary report on the geology of Florida with
special reference to the stratigraphy: Florida Geol. Survey 2d Ann.
Rept., 1908-09, p. 25-173.
1913 (and Sanford, Samuel) Geology and ground waters of Florida: U. S.
Geol. Survey Water-Supply Paper 319.
Mossom, Stuart (see Cooke, C. W.)
Parker, G. G.
1955 (and Ferguson, G. E., and Love, S. K., and others) Water resources of
southeastern Florida with special reference to the geology and ground
water of the Miami area: U. S. Geol. Survey Water-Supply Paper 1255.
Poole, J. L. (see Krieger, R. A.)
Puri, Harbans, S.
1953 Zonation of the Ocala group in peninsular Florida (abstract): Jour. Sed.
Petrology, v. 23, p. 130.
Rainwater, F. H.
1960 (and Thatcher, L. L.) Methods for collection and analysis of water sam-
ples: U. S. Geol. Survey Water-Supply Paper 1454.
Sanford, Samuel (see Matson, G. C.)
Scarborough, E. F. (see Scruggs, F. H.)
Scruggs, F. H.
1953 (and Scarborough, E. F.) Annual fruit and vegetable report; production,
transportation, and marketing analysis: Florida State Marketing Bur.,
Jacksonville, Florida.
Sellards, E. H.
1913 (and Gunter, Herman) The artesian water supply of eastern and southern
Florida: Florida Geol. Survey 5th Ann. Rept.
Stringfield, V. T.
1934 Ground water in Seminole County, Florida: Florida Geol. Survey Rept.
Inv. 1.
1936 Artesian water in the Florida peninsula: U. S. Geol. Survey Water-Supply
Paper 773-C.
Stubbs, S. A.
1937 A study of the artesian water supply of Seminole County, Florida: Florida
Acad. Sci. Proc, v. 2.
Thatcher, L. L. (see Rainwater, F. H.)
Unklesbay, A. G.
1944 Ground-water conditions in Orlando and vicinity, Florida: Florida Geol.
Survey Rept. Inv. 5.
Vernon, R. 0. (see also Ferguson, G. E.)
1951 Geology of Citrus and Levy counties, Florida: Florida Geol. Survey
Bull. 33.






REPORT OF INVESTIGATIONS No. 27 91

Wenzell, L. K.
1942 Methods for determining permeability of water-bearing materials, with
special reference to discharging well methods, with a section on direct
laboratory methods and bibliography on permeability and laminar flow,
by V. C. Fishel: U. S. Geol. Survey Water-Supply Paper 887.
Westgate, P. J.
1950 Effects of soluble soil salts on vegetable production at Sanford: Florida
State Hort. Soc. Proc., Oct.-Nov. 1950.
Wyrick, G. G.
1956 (and Leutze, W. P.) Interim report on ground-water resources of the
northeastern part of Volusia County, Florida: Florida Geol. Survey Inf.
Circ. 8.
1960 The ground-water resources of Volusia County, Florida: Florida Geol.
Survey Rept. Inv. 22.












',ED STATES DEPARTMENT OF INTERIOR FLORIDA GEOLOGICAL SURVEY REPORT OF INVESTIGATIONS NO. 27
GEOLOGICAL SURVEY R. O. Vernon, Director
R 29 E R 30 E R 31 E R 32 E R 33 E

8125' 8120' 81015' 81101 8105' 8100'
EXPLANATION A A'
0 6
29 Line of geologic section
Well (Upper number is well number; lower
number is altitude of the top of the Note: Missing well number indicates that
V O Eocene limestone, in feet, below mean the ///iude of the top of the
sea level.) Eocene limestone was token from
SeS geologic logs Interpreted by Sidney A
e/ 25 Stubbs. (1937)
TU D LAK KE MONROE Contour line represents altitude of the top of T
,- 28050' / -"B MONROE 0- -- -_ "- O the Eocene limestone, in feet, below VOl/ 28050'-19
t__ Ic , 8115 8 881 0'
80 mean sea levei S/4

o I E I 25-3 EO | R
i c 055 Fault
toI SANFORD 415 D= Down CODpp

i 4. Contour interval 25ft.
PAOLA 05 D D























25 42 40
20 I










OO LAKE MARY COU
10 LARNEY

T !55
0NGENEVA2COUN
425
















825 820 805' 80 815' 81000'
Z I 5101o






















R 29 E R 30 E R 31 E I R 32 E R 33 E


1se o3nf from maps ofG
-r c Se Rod Deportment Geology by Jck Brrcough

Figure 4. Configuration and altitude of the top of the Eocene limestones.
Figure 4. Configuration and altitude of the top of the Eocene limestones.












S-E 5-TES DEPARTMENT OF INTERIOR FLORIDA GEOLOGICAL SURVEY REPORT OF INVESTIGATIONS NO. 27
ECOLOGICAL SURVEY R.O. Vernon, Director

R 29 E R 30 E R 31 E R 32 E R 33 E

81025' 81020' 81015' 81010' 81005' 8100'
EXPLANATION
5
27
SWell(Upper number is well number; lower
^ number is altitude of the top of the Note- Missing well number indicates that
J v O o 1 Avon Pork limestone, in feet, below the altitude of the top of the
0 mean sea level. Avon Pork limestone was token
C 2- from geologic logs interpreted by
/ 25 Sidney A. Stubbs. (1937)
SL IKE MONROE O Contour line represents altitude of the top 5
-_=09I 0 of the Avon Pork limestone, in feet, '0Ll 2850-
.- tE below mean sea level. S C

25 81201 85 NFoP8101 8505- 800
Fault
'- ,D=Down
9 8 D U=Up














































I-------- -- I I I I 1 I -- --- I I--- I I---- L -I---------------------!-

c u'ru o Geology by Jack T. Brraclough.
PAOL Deprtment





















Figure 5. Configuration and altitude of the top of the Avon Park Limestone.
104 8


LAKE MARY

/00 HARNEY
427/ 28045'- T
0 20









125
150 wOO







/000 OVIEDO 75 C00


AO 200



17 0 0 426 a. gooe0d0prnn

434
2E32MILES 225
L - ------
O R ANGE CO U NTY
81025' 81"20' 81015' 81010' 81005' 81000'

R 29 E R 30 E R 31 E R 32 E R 33 E

e we 'ram mavs of Geology by Jack T.Borraciough
_s ue Rocd Department.

Figure 5. Configuration and altitude of the top of the Avon Park Limestone.









S:STATES DEPARTMENT OF INTERIOR
GEOLOGICAL SURVEY


FLORIDA GEOLOGICAL SURVEY
R.O. Vernon. Director


REPORT OF INVESTIGATIONS NO. 27


R 29 E

81025'


R 30 E


R 31 E


R 32 E


R 33 E


81010'


EXPLANATION


Well (Upper number is well number; lower
number is altitude of the piezometric
surface in feet above mean sea level.)


-25
0 Contour line showing the altitude of the piezometric
surface in feet above mean sea level

. Contour interval 5 ft.


a 2S
SCALE


R 31 F


3ase r:'en rrom maps or
'orda State Road DepOrtment


Hydmilogy by Jck T. Borroclough-


Figure 7. The Piezometric surface of the Floridan aquifer in January 1954.


29 E


R 30 E


R AP C


I I I I-II I I -- I---~ II~L


lot rT3 C


:3,












'ED STATES DEPARTMENT OF INTERIOR FLORIDA GEOLOGICAL SURVEY REPORT OF INVESTIGATIONS NO. 27
GEOLOGICAL SURVEY RO.Vernon, Director
R 29 E R 30 E R 31 E R 32 E R 33 E
1II I -iI I~l

81"25' 81020 81 15' 81010' 81005' 81000'

EXPLANATION

*9
N) 1/0 Well(Upper number is well number; lower
number is altitude of the piezometric
(I surface, in feet, above mean sea level

v204 .AKE MONROE 0 25 T
-2S050' 25 0O Contour line showing the altitude of the piezometric 1O[ 0 280 50'- 9
-2S50' zs--. VbuI
8KE surface, in feet, above mean seoa level Sl4
E 0S
30,Z contour interval 5 ft
46.1
31 0 Z8 27
4 7
-17-L, 0 -LHARNEY


-~T2 21- -
T- -1 -1 JOHIVS

.7 9 2/9-__ .T I-





/2o5/ 28o45'- T
?4*79-- LAKE













OR2*
02 FE2Lo
























436 LTAMONTE PARK/
I 7 I 1~--3 21












28~~2 40 A. 9'O o4
-21 0 C21 10
















11' ,9 -
Il
















0 6-,,Ds Nt.\21

_ALE L ,S

















ORANGE COUNTY
LMLA





































R 29 ER 30 E R 1 E I R 32 E R 33 E


acse tonen from maps of Hydrology by Jack T. Borraclough
MAc f H N





















-r a State Ro0d Depar6tment


















Figure 8. The Piezometric surface of the Floridan aquifer in June 1956.
VER425 2-

4 4
2 *3'
L~twOODo4




4_4 19 19 2
CD, a 15
-50 FERN r
4 &I~hONTE PA~RK a:
9 A PRINGS
2804d4 OVIEDO 4d -0


a~~ 419
4

43 40 8 0111J. -
E3 ~449 3
45 \ J9

0 1 2 3 MIlLES Il I
SCILE

0 R A\ N G E C 0 U N T Y
81025' 81020' W615 81010, 81005' 81"000'

R 29 E R 30 E R 31 E R 32 E R 33 E

:Icsa 'axen from maps of Hdooyb okT arcog
sa State Road Department Hdooyb Jc arc
Figure 8. The Piezometric surface of the Floridan aquifer in June 1956.









MTED STATES DEPARTMENT OF INTERIOR FLORIDA GEOLOGICAL SURVEY REPORT OF INVESTIGATIONS NO. 27
GEOLOGICAL SURVEY R 0. Vernon- Director

R 29 E R 30 E R 31 E R 32 E R 33 E

81025 8120' 8115' 8110' 810051 81000'

EXPLANATION



Area of artesian flow

T E, KE MONROE in Line of equal height of the piezometric, in feet
2- 2850' 2805 o0bove or below land surface vO 2850'-
o 0 LAK EGInterval 10 feet S





oro. ,,sPAOLA -R D






LAKE

MAR IToHGRENEY

F-2 45's o 45 T0



















.. .oe to Sr
422





























29 E R 30 EIR 31 R 32 E R 33 E.




referred to land surface in 1954.
ase hen from map of ydrlogy by ack B rrac4ug
or d Stte Rad eparmen

Fiue .Ara o rtsanfowad h eih o hepezmtrcsufce1n0et
zeere tVan urae n194









_FITED STATES DEPARTMENT OF INTERIOR FLORIDA GEOLOGICAL SURVEY REPORT OF INVESTIGATIONS NO. 27
GEOLOGICAL SURVEY R. O. Vernon, Director
R 29 E R 30 E R 31 E R 32 E R 33 E

810256I 81o20' 81 05' 8110o' 8005' 81000'
EXPLANATION


Well (Upper number is well number. Lower number is dissolved
3 O T 1 solids content in parts per million).
:1 -DISSOLVED SOLIDS
(ports per million)


-28050 {K0O 28050

5 8 1ONROE SPRNGS900C4


_SANFOR 4



,/50 I.\
/-0 PAOLA 10-HAS
0 5





a-*o L1 LAKE
e MARY

.-845o HARNEY

ORA G CO U N




S450









R 263 E563OA 32 R V
Sa Ro DepNGSOVIEDO 4te

F2h1h
I 4264




450.9- 10














o3so MUESox
0 E15E8 160 NO S











-L E ALTAMO NTE 490-

O7RSANGE COUNTY
8425' 8P20' 8o5' 8Io' 8O5' 8ooo





1R 29 E R 30 E R 31 E R 32 E R 33 E

rase take1 from mo2s of Hydrology by Jack I Barroc6ough
-aa1 2 3 Stole Roa8 Department
3asetaien fom aps f Hdrolgy y Jak TBarrclo
or~d Stoe Rad Dpartent
Fiue.1 Tedsovd-oiscnen fwtrfrmteFoidnaufr







UF7TED STATES DEPARTMENT OF INTERIOR FLORIDA GEOLOGICAL SURVEY REPORT OF INVESTIGATIONS NO. 27
GEDLOGICAL SURVEY R. O. Vernon, Director
R 29 E I R 30 E R 31 E I R 32 E R 33 E

8P25' 8120' 81 15' 810 0' 8105'. 81000'
EXPLANATION


Well (Upper number is well number. Lower number is dissolved
O` O solids content in parts per million).


S 2850, AKE2850







//"i PAOLA 9

M E NROOE,







S28045
OR- P,480 'A _
M56I 1,001- More than 3,0000










1 67 27o

4 PAOLA 9 4--



__0 50





0201-A2 1 f48"



"no 20 L4 1
240j 4Z? 28045'0















70 0/o0 620. .-












O RANGE COUNTY
81025' 8120' 81l5' 81o10' 81005' 81000
R 29 E I R 30 E I R 31 E I R 32 E R 33 E


1ase tohen from maps of Hydrology by Jock T Borroclough.
Aoda StYle Rood Deprtment.
Figure 31. The dissolved-solids content of water from the Floridan aquifer.
3m okntrmmage 3 olg b oc Brcluh
z~and StosRoadDeparFen6
FiueS1 h isovdso150 9n f ae ro h Foia aufr








UNITED STATES DEPARTMENT OF INTERIOR FLORIDA GEOLOGICAL SURVEY REPORT OF INVESTIGATIONS NO. 27
GEOLOGICAL SURVEY R.O. Vernon, Director

R 29 E R 30 E R 3[ E R 32 E R 33 E

81"25 81"20' 81 15' 81' 8105' 8100'
EXPLANATION


Well (Upper number is well number. Ldwer number
0`V0 C : is hardness in parts per million).
HARDNESS
Sports per million)




MoNR I I IT T








-00
81 2=8=0=8 0 58 0201-500 M ore th8n 5 0 0 '81 0 0



.90 4 A I I I I I I I
PAOLA 3 JOHNS
993


2 W3 o
6*99 344
3 99 5

*- ,
ELAKE


2845 HARNEY
-5 o / 2845 1
2T 4-0o 2s s 0
S440 1ENEVA 6R S



O/2 8024 ?,050
1 4\

5 /

LOGOD 0 LONGWOOD*514
44 1E8O168 i45 2



4 aERN PARK s3
17 ALTAMONTE e
28040 SPRINGS
32 OVIEDO 4


2 E16 419 1752 33 72

CHULUOTA 104

S / -- Im so


o 0 1 2 3 nILES 26 01






:acse uken from maps of
landa State Road Department Hydrology by Jack T Barroclough

Figure 82. Showing the hardness of water from the Floridan aquifer.








UNITED STATES DEPARTMENT OF INTERIOR


FLORIDA GEOLOGICAL SURVEY
R.O. Vernon, Director


81"25'


81"10'


REPORT OF INVESTIGATIONS NO. 27


81005'


EXPLANATION
Area in which the land surface is less than 30
feet above mean sea level.


Area in which the artesian water has a chloride
S content of more than 250 parts per million


1 0 I 2 3 MILES


COUNTY


Base taxen from maps of
'or:du State Road Department


Hydrology by Jock T. Borroclough.


Figure 35. The relationship of the chloride content of artesian water to the land-
surface altitude.


28"50'


81"25







'%ITED STATES DEPARTMENT OF INTERIOR FLORIDA GEOLOGICAL SURVEY REPORT OF INVESTIGATIONS NO. 27
GEOLOGICAL SURVEY R. O. Vernon, Director
R 29 E R 30 E R '31 E R 32 E R 33 E

81W25' 81020' 81015' 81010' 81005' 81000'
EXPLANATION
CHLORIDE CONTENT Note:
(parts per million) Control based on chloride analyses of
water from 763 wells but only 139
VO wells are shown on map.
SLess than 25 26 250

29050 1.860
250OL285019
5 I E. t 251 1,000 1,001-5,000oo1S
S__ { _8'





CO NT
R 2 I
A m or More than 5,000 b
19-415


























F 3 h oa o t Florid aquifer.
PLOLANT LI 750 JOHNs








160

0NEVA 2 28045'

C! o







02551 20IO 8
151




E IiE 1 -447-c
FERN RO







R 29 R 0ALTAMONTE E R 31 E R 32 E R 33 E90
Iand S eSPRINGS pment










Figure 36. The chloride content of water fiom the upper part of the Floridan aquifer.





e;- : 5-TES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY


FLORIDA GEOLOGICAL SURVEY
WA r M- 4-


K.U.Vernon, D i rec o
293 F I0 I


81,020


C .


t I-L--~ I- +o 1 4 4. 1


Al


(


4gj7
3...


4 O


, L


S7


SL
*5 U-24`
*ST


KE WO(NRC
513 z
9f7~


'/
/LAKL


S MOPNROE


I.
I:I


r 31 t_


I I J-


29 I R M F0 721'
S29 E I LT~m iu i~ nJnjnn I Li ',


81015' 81010' 81005


1 I 100
8100'


EXPLANATION


Well


m. .7


C7
-'
1-

Z '

A~~~6
' rL


INSET "A"
81013'


28z4-;- -, 28-4B
903] 4
S 23 0 mile
INSET SCALE

L2 0
33 S


K1^ h


UL UNs


C3-,
'I
",.'/ ,


_ _ ~ .85IISE 1 2r/ .3 1*71 _ _ _
I J.

7 I II




-;~~~~ NE A5 55 .IaI
1 4 9.." .1

6.! __ 2







*. -3U
434








'4
li X p l rw.
(!::r_ rd Io










2 3 -
Z-6 CRE4T Cr' ~ / 4 3.
15. ,195..
LIL











* r r~ 7 2*
I c) _/_i.V_ 4,

L .3 ii(25
ID ..2'
.7 GENEn
7- rrF



1.7 3. 2 I
RESL WAGNER 4 .3.
=:G .
i? n OOD
/ : 5 '.5
a9.,.r
434
i I -1I II I "w '2


S3 2 MILES
-`I ,


SCALE


81020'


GOLDENROD


k65
V32/" .!


LA lA


--4


I .HUL


rF


JOTA


I~ ~ ~ ~~ I K III lnl.~


7 1ft t, 1 t -R 4 1


- 1-
81015'


\IGE


-I-i
81010n


- I-COUNTY
COUNTY


FiuR e12 Ec I R of E
Figure 10. Locations of Wells.


I- O1 I-


8125'


S280 50-


i'r


K' R


____ 11 1


81025'


Li


i'


i .A -, I I .


4%1N


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Ground-water resources of Seminole County, Florida ( FGS: Report of investigations 27 )
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 Material Information
Title: Ground-water resources of Seminole County, Florida ( FGS: Report of investigations 27 )
Series Title: ( FGS: Report of investigations 27 )
Physical Description: viii, 91 p. : illus., maps (part fold. in pocket) diagrs., tables. ; 23 cm.
Language: English
Creator: Barraclough, Jack T
Geological Survey (U.S.)
Florida Geological Survey
Publisher: s.n.
Place of Publication: Tallahassee
Publication Date: 1962
 Subjects
Subjects / Keywords: Groundwater -- Florida -- Seminole County   ( lcsh )
Water-supply -- Florida -- Seminole County   ( lcsh )
Water supply -- Seminole County
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: "References": p. 89-91.
General Note: "Prepared by the United States Geological Survey, in cooperation with the Florida Geological Survey, the Board of County Commissioners of Seminole County, and the city of Sanford."
 Record Information
Source Institution: University of Florida
Rights Management:
The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: aleph - 000958536
oclc - 01732630
notis - AES1346
lccn - a 63007029
System ID: UF00001214:00001

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Table of Contents
    Front Cover
        Page i
    Florida State Board of Conservation
        Page ii
    Transmittal letter
        Page iii
        Page iv
    Contents
        Page v
        Page vi
        Page vii
        Page viii
    Abstract
        Page 1
        Page 2
    Introduction
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
    Geography
        Page 7
        Page 8
        Page 9
        Page 6
    Geology
        Page 10
        Page 11
        Page 9
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
    Ground water
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 18
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
    Surface water
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 34
    Well exploration
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 44
        Page 54
        Page 55
    Quality of water
        Page 56
        Page 57
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 55
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
    Salt-water contamination
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
        Page 79
        Page 80
    Quantitative studies
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
        Page 80
    Summary and conclusions
        Page 87
        Page 88
    References
        Page 89
        Page 90
        Page 91
    Figures
        Page 92
        Page 93
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
        Page 100
        Page 101
        Page 102
        Copyright
            Copyright
Full Text


STATE OF FLORIDA

STATE BOARD OF CONSERVATION

DIVISION OF GEOLOGY



FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director



REPORT OF INVESTIGATIONS NO. 27



GROUND-WATER RESOURCES

OF

SEMINOLE COUNTY, FLORIDA


By
Jack T. Barraclough
U. S. Geological Survey


THE BOARD


Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
FLORIDA GEOLOGICAL SURVEY,
OF COUNTY COMMISSIONERS OF SEMINOLE COUNTY
and the
CITY OF SANFORD


TALLAHASSEE
1962










AGIU.
CULTURAL
LBRARy

FLORIDA STATE BOARD

OF

CONSERVATION


FARRIS BRYANT
Governor


TOM ADAMS
Secretary of State



J. EDWIN LARSON
Treasurer



THOMAS D. BAILEY
Superintendent of Public Instruction


RICHARD ERVIN
Attorney General



RAY E. GREEN
Comptroller



DOYLE CONNER
Commissioner of Agriculture


W. RANDOLPH HODGES
Director








LETTER OF TRANSMITTAL


)^/{fcdi i ealoyd cai & tavey

Tallahassee
November 1, 1961



Honorable Farris Bryant, Chairman
Florida State Board of Conservation
Tallahassee, Florida
Dear Governor Bryant:
The Division of Geology is pleased to publish, as Florida Geological
Survey Report of Investigations No. 27, a study of the "Ground-Water
Resources of Seminole County, Florida." The study was made by Jack
T. Barraclough, engineer with the U. S. Geological Survey, in coopera-
tion with the Division of Geology, Seminole County commissioners, and
the city of Sanford.
The limestones of the principal artesian aquifer underlie all of
Seminole County and provide the water required for the extensive
farming and industry of the county. This water probably originates in the
recharge area of Polk and Orange counties and from local rainfall. The
report has determined the long-range changes of water levels, provided
seasonal fluctuations and related these to quality-of-water changes.
The study will provide the data required for expansion of pumping,
location of well fields, and treatment of water.

Respectfully yours
Robert O. Vernon, Director
and State Geologist






























Complete manuscript received
July 14, 1961

Published for the Florida Geological Survey by
Rose Printing Company, Inc.
Tallahassee
November 1, 1961










Abstract
Introduction
Purpose 'and scope of investigation
Location and extent of area
Previous investigations
Acknowledgments
Well-numbering system
Geography
Topography and drainage
Climate -
Population and development
Geology
Stratigraphy
Pre-Mesozoic rocks
Eocene series
Lake City limestone
Avon Park limestone
Ocala group
Miocene series
Hawthorn formation
Pliocene or upper Miocene deposits
Pleistocene and Recent deposits
Structure


Ground water
Nonartesian aquifer
Artesian aquifer
Piezometric surface in
Piezometric surface in
Area of artesian flow
Wells
Subirrigation
Water-level records


Florida _
Seminole County


Surface water
Springs
Artesian springs
Water-table springs
Lakes


Well exploration
Electric logs
Resistivity, flow, salinity,


and temperature measurements ___


Quality of water
Color
Specific conductance
Silica
Iron
Calcium
Magnesium
Sodium and potassium
Bicarbonate


CONTENTS


Page
1
2
2
3
3
5
6


18
19
19
20
22
23
23
26
28


- ----- ---- -


- -- - -. --


____ I__~_~_






Sulfate 64
Chloride 64
Fnuoride 67
Nitrate 67
Dissolved solids 67
Hardness 68
Hydrogen sulfide 69
Hydrogen-ion concentration 69
Chemical character of ground water 69
Salt-water contamination 71
Quantitative studies ______---- --- 80
Summary and conclusions 87
References -- 89






ILLUSTRATIONS -
Figure Page
1. Location of Seminole County --____ 4
2. Monthly distribution of rainfall at Sanford 8
3. Geologic units penetrated by water wells in Seminole County 11
4. Configuration and altitude of the top of the Eocene limestones In pocket
5. Configuration and altitude of the top of the Avon Park Limestone In pocket
6. The piezometric surface of the Floridan aquifer 21
7. The piezometric surface of the Floridan aquifer in January 1954 In pocket
8. The piezometric surface of the Floridan aquifer in June 1956 __ In pocket
9. Areas of artesian flow and the height of the piezometric
surface, in feet, referred to land surface in 1954 In pocket
10. Location of wells In pocket
11. Relation between the static head and the yield of four flowing artesian
wells in the area around Sanford 25
12. Relation between the static head and the yield of four flowing artesian
wells in the eastern part of Seminole County 27
13. Hydrographs of the daily high water levels in wells 841-121-1 and 847-
113-6 and the monthly rainfall at Sanford 29
14. Hydrographs of wells 841-113-1, 842-117-2, 843-118-2, 844-117-2, 846-
116-11, and the monthly rainfall at Sanford ___________ 31
15. Hydrographs of wells 838-113-2, 839-113-1, 840-112-1, 844-115-8, 848-
119-4, and 849-118-5 32
16. Hydrographs of wells 846-123-2 and 847-123-2, about 1% miles ,west of
Paola. ___. 34
17. Sweet Water Spring:
a. View of spring and surrounding area 36
b. Closeup view of spring 37
18. Heath Spring, 0.7 mile northwest of Geneva 38
19. Temperature and chloride content of Heath Spring 39
20. Hydrographs of five lakes in. Seminole County 40
21. Lake Geneva showing the low water level on August 13, 1957. __ 42
22. Hydrographs of wells 839-122-1, 840-120-2, and Lake Orienta 43
23. Electric log, current-meter traverse, and chloride content of water from
well 845-117-10, 3.6 miles south of Sanford 45
24. Electric log, current-meter traverse, and chloride content of water from
well 840-107-2, 2.1 miles north of Chuluota. 47
25. Electric log and chloride content of water from well 848-116-12, 0.5 mile
southwest of Sanford. 48
26. Electric log, current-meter traverse, and chloride content of water from
well 841-110-12, 2.7 miles northeast of Oviedo ______ 49
27. Electric log and current-meter traverse in well 838-113-3, 2.5 miles south
east of Oviedo. 50


vii






28. Electric log, current-meter traverse, chloride content, temperature, and
yield of water from well 842-111-6, 2.3 miles northeast of Oviedo -- 51
29. Electric log and chloride content of water from well 847-113-31, 3.0
miles southeast of Sanford. ___- 53
30. Current-meter traverse and chloride content of water from wells 842-
112-2, 2.3 miles northeast of Oviedo, and 842-111-7, 2.3 miles northeast
of Oviedo. 54
31. The dissolved-solids content of water from the Floridan aquifer. In pocket
32. The hardness of water from the Floridan aquifer. In pocket
33. Bar graphs of the chemical analyses of water from 20 artesian wells and
3 springs. 70
34. The relationship of the chemical constituents in ground water to the
distance of the wells from a recharge area centered near Golden and
Silver lakes. 71
35. The relationship of the chloride content of artesian water to the land-
surface altitude ___ In pocket
36. The chloride content of water from the upper part of the
Floridan aquifer. In pocket
37. Hydrographs and chloride content of water from wells 844-114-1, 844-
116-1, and 845-113-1. 74
38. Hydrographs and chloride content of water from wells 848-116-2, 848-
117-8, and 849-119-3. 76
39. Hydrographs and chloride content of water from wells 841-110-9 and
841-110-12. 77
40- Hydrographs and chloride content of water from wells 842-112-1 and
846-112-5. --- 78
41. Data from wells 842-110-2, 843-103-4, 845-113-10, and 848-113-1. -__ 79
42. Data from wells 841-110-1, 841-111-1, and 849-117-1. 81
43. Flow-measuring apparatus 82
44. Semilog plot of recovery versus time in well 841-113-3. ----------- 84
45. Theoretical drawdowns in the vicinity of a well being pumped at a rate
of 1,000 gpm for selected periods of time ------------ -- 86

TABLES
Table Page
1. Geologic units in Seminole County 10
2. Use of inventoried wells 24
3. Diameter of inventoried wells _____ 24
4. Chemical analyses of water from wells in Seminole County 57
5. Chloride content of water samples collected at various depths in wells 65
6. Chloride content of water that was collected as wells were being drilled 66
7. Data from recovery tests of artesian wells in Seminole County __ 84






GROUND-WATER RESOURCES OF
SEMINOLE COUNTY, FLORIDA
By
JACK T. BARRACLOUGH

ABSTRACT

Seminole County is in the east-central part of the Florida Peninsula.
The climate is subtropical and the average annual rainfall is more than
50 inches. The area is well suited for the growing of winter vegetables,
even though most of the rain falls during the summer months and the
vegetables must be irrigated.
The surface deposits consist of sand of Pleistocene and Recent Age,
which ranges in thickness from 10 to 75 feet. Beneath this sand are depos-
its of clay and shell beds, which are believed to be of late Miocene or
Pliocene Age. The Hawthorn Formation of middle Miocene Age under-
lies the surface sand where the deposits of clay and shells are absent.
A thick section of limestone of Eocene Age underlies the Hawthorn For-
mation, and, where the Hawthorn is absent, the limestone underlies the
clay and shells of late Miocene or Pliocene Age. The sedimentary rocks
extend to about 6,000 feet below sea level in Seminole County.
The upper part of the limestone section is composed, in descending
order, of the Ocala Group' of late Eocene Age, the Avon Park Limestone
of late middle Eocene Age, and the Lake City Limestone of early mid-
dle Eocene Age.
The section of limestone formations described above and the lower
part of the Hawthorn Formation make up part of the Floridan aquifer,
which is the most important source of ground water in Seminole County.
Water in the Floridan aquifer is under artesian pressure, and wells that
penetrate this aquifer flow at the surface in most of the lowland areas.
The water in the Floridan aquifer in Seminole County is recharged in
Polk, Orange, and Seminole counties.
Fluctuations of artesian pressure in Seminole County result mainly
from differences in rainfall and variations in the rate of withdrawal of
water from wells. In the Oviedo area the seasonal fluctuations of artesian
pressures cause the water level to fluctuate as much as 12 feet. In the
Sanford area, the maximum seasonal fluctuation of water level was about
7 feet. The minimum seasonal fluctuation of water level in the county
was generally between 5 and 6 feet.

'The stratigraphic nomenclature used in this report conforms to the usage of
the Florida Geological Survey.






FLORIDA GEOLOGICAL SURVEY


Comparisons of water-level measurements made during the period
1983-39 with measurements made during the period 1951-56 show that
the average decline of the water level in the Sanford area, in the interval
between those two periods, was about 1 foot. During the same interval,
the average decline of the water level in the Oviedo area was about 3
feet.
The chloride content of water from artesian wells in Seminole County
ranges generally from 5 ppm (parts per million) in the recharge areas
near the towns of Lake Mary, Paola, Longwood, Oviedo, Chuluota, and
Geneva to 7,500 ppm in the area near Mullet Lake. In most of the two
truck farming areas of Sanford and Oviedo, the chloride content of the
water from artesian wells ranges in different areas from about 10 ppm to
slightly more than 1,500 ppm. The minimum observed seasonal variation
of the chloride content of the artesian water in one well near Sanford was
35 ppm and the maximum observed seasonal variation in one well was
265 ppm. The minimum observed seasonal variation of the chloride con-
tent of the artesian water in one well near Oviedo was 16 ppm and the
maximum observed seasonal variation in one well was 180 ppm. Com-
parisons of analyses made in 1933 and 1956 indicate that there has been
little long-term change in the chloride content of the artesian water in
Seminole County.
Chemical analyses show that ground water in parts of Seminole Coun-
tv would be classed as excellent for most uses, and ground water in other
parts of the county would be classed as unusable for almost all purposes.
The artesian aquifer has an average coefficient of transmissibility of
about 185,000 gpd (gallons per day) per foot.

INTRODUCTION
PURPOSE AND SCOPE OF INVESTIGATION
Salt-water encroachment is a problem of great concern to most users
of ground water in Florida. In many coastal areas the lowering of water
levels by heavy pumping contributes to lateral encroachment of salt
water from the ocean. In some inland areas the water-bearing forma-
tions contain salty water at a moderate depth and excessive lowering
of water levels causes upward encroachment of the salty water. Exam-
ples of inland areas with salt-water problems can be found. along most
of the St. Johns River.
An important part of the economy of Seminole County is the growing
and marketing of winter vegetables. The most important farming areas
are in the level lowlands adjacent to Lake Monroe and Lake Jessup,
where adequate supplies of water for irrigation are available from the






FLORIDA GEOLOGICAL SURVEY


Comparisons of water-level measurements made during the period
1983-39 with measurements made during the period 1951-56 show that
the average decline of the water level in the Sanford area, in the interval
between those two periods, was about 1 foot. During the same interval,
the average decline of the water level in the Oviedo area was about 3
feet.
The chloride content of water from artesian wells in Seminole County
ranges generally from 5 ppm (parts per million) in the recharge areas
near the towns of Lake Mary, Paola, Longwood, Oviedo, Chuluota, and
Geneva to 7,500 ppm in the area near Mullet Lake. In most of the two
truck farming areas of Sanford and Oviedo, the chloride content of the
water from artesian wells ranges in different areas from about 10 ppm to
slightly more than 1,500 ppm. The minimum observed seasonal variation
of the chloride content of the artesian water in one well near Sanford was
35 ppm and the maximum observed seasonal variation in one well was
265 ppm. The minimum observed seasonal variation of the chloride con-
tent of the artesian water in one well near Oviedo was 16 ppm and the
maximum observed seasonal variation in one well was 180 ppm. Com-
parisons of analyses made in 1933 and 1956 indicate that there has been
little long-term change in the chloride content of the artesian water in
Seminole County.
Chemical analyses show that ground water in parts of Seminole Coun-
tv would be classed as excellent for most uses, and ground water in other
parts of the county would be classed as unusable for almost all purposes.
The artesian aquifer has an average coefficient of transmissibility of
about 185,000 gpd (gallons per day) per foot.

INTRODUCTION
PURPOSE AND SCOPE OF INVESTIGATION
Salt-water encroachment is a problem of great concern to most users
of ground water in Florida. In many coastal areas the lowering of water
levels by heavy pumping contributes to lateral encroachment of salt
water from the ocean. In some inland areas the water-bearing forma-
tions contain salty water at a moderate depth and excessive lowering
of water levels causes upward encroachment of the salty water. Exam-
ples of inland areas with salt-water problems can be found. along most
of the St. Johns River.
An important part of the economy of Seminole County is the growing
and marketing of winter vegetables. The most important farming areas
are in the level lowlands adjacent to Lake Monroe and Lake Jessup,
where adequate supplies of water for irrigation are available from the






REPORT OF INVESTIGATIONS No. 27


natural flow of artesian wells. In parts of the farming areas wells yield
relatively salty water and, locally, the artesian pressure has declined
excessively as a result of heavy withdrawal of water for irrigation and
for vegetable processing. This decline in artesian pressure has resulted
in a decrease in the size of the area of artesian flow and, in some places,
has necessitated the use of pumps on wells that formerly produced an
adequate supply of water by natural flow. The decline of artesian pres-
sure may lead also to contamination of the existing supplies by causing
encroachment of salty water from the formations that underlie the pro-
ducing aquifer.
Recognizing these possibilities, the Board of County Commissioners
of Seminole County requested the U. S. Geological Survey and the Florida
Geological Survey to make an investigation of the ground-water resources
of the county. An investigation was begun in October 1951 by the U. S.
Geological Survey in cooperation with the Florida Geological Survey and
the Board of County Commissioners of Seminole County. The city of
Sanford shared in the cooperation from 1953 through 1955.
The principal purpose of the investigation was to collect and inter-
pret basic information for the safe and efficient development of ground-
water supplies of Seminole County. Special emphasis was placed on the
problems associated with salt-water contamination and declining water
levels.
The field work was begun in 1951 by Ralph C. Health, geologist, under
the direct supervision of H. H. Cooper, Jr., district engineer. The author
was assigned to the project in 1953, under the direct supervision of Mr.
Heath, who was then acting district geologist of the Federal Survey. Dur-
ing the period 1955-58, the investigation was under the direct supervision
of M. I. Rorabaugh, district engineer.

LOCATION AND EXTENT OF AREA
Seminole County comprises an area of about 821 square miles in the
east-central part of the Florida Peninsula (fig. 1). Prior to 1913 the area
in this report was part of Orange County. Sanford, the county seat, is in
the northern part of Seminole County, along the St. Johns River.

PREVIOUS INVESTIGATIONS
The geology and ground-water resources of Seminole County are
described in several reports published by the Florida Geological Survey,
the Florida Academy of Sciences, and the U. S. Geological Survey.
A report by Matson and Sanford (1913, p. 876-881) contains a brief
discussion of the geology and ground-water resources of Orange County,
which at that time included the area that is now Seminole County. A






4 FLORIDA GEOLOGICAL SURVEY


Figure 1. Location of Seminole County.







REPORT OF INVESTIGATIONS No. 27


report by Sellards and Gunter (1913, p. 113) contains information on
wells in Seminole County.
V. T. Stringfield (1984) made a brief investigation of the ground-
water resources of Seminole County as part of a general investigation
of the ground-water resources of the Florida Peninsula. The geology and
ground water of Seminole County are also discussed by Stringfield (1936,
p. 135-136, 162, 174, 188) in a report on the artesian water in the Florida
Peninsula. This report includes a map showing the areas of artesian flow,
a map showing the areas in which the artesian water contains more than
100 ppm of chloride, and the first published map of the piezometric
surface of the principal artesian (Floridan) aquifer. A report on the
geology and artesian-water supply of Seminole County by Stubbs (1937,
p. 24-36) includes two maps of the piezometric surface, a map showing
the areas of artesian flow, and a discussion of the geologic formations
that underlie the county. As a part of his work in the county, Stubbs
periodically measured the water levels in selected wells and analysed
the chloride content of water samples collected from selected wells
(S. A. Stubbs and Irving Feinberg, unpublished records in the files of
H. James Gut, Sanford, Florida).
A report by Unklesbay (1944), describing ground-water conditions
in Orlando and vicinity, includes records of 3 wells and 1 spring in Sem-
inole County. The geology of the State, including formations in Seminole
County, is described in a report by Cooke (1945, p. 225).
A report by Ferguson and others (1947, p. 149-154) contains de-
scriptions of three of the largest springs in the county and chemical
analyses of their waters. Chemical analyses of water from wells in Sem-
inole County are contained in reports by Collins and Howard (1928,
p. 228) and Black and Brown (1951, p. 104).
Heath and Barraclough (1954) prepared an interim report on the
ground-water resources of Seminole County as a part of this investi-
gation.
ACKNOWLEDGMENTS
The author wishes to express appreciation to the many residents of
the county who readily gave information regarding their wells, and to
those who permitted frequent measurements of water levels in their
wells.
Mr. H. James Gut, former mayor and former city commissioner of
Sanford, was chiefly responsible for the initiation of the investigation.
In addition, Mr. Gut thoughtfully saved valuable information collected
by Sidney A. Stubbs in 1937 and furnished these data and other informa-
tion from his files for use during the investigation.







FLORIDA GEOLOGICAL SURVEY


Thanks are extended to others in the county who have been especially
helpful. These men include: Mr. C. S. Lee, Oviedo; Dr. Phillip Westgate,
Central Florida Experiment Station, Sanford; Mr. Benjamin Wiggins, Soil
Conservation Service, Sanford; Mr. Randall Chase, Sanford; and Mr.
LeRoy Hennessey, Longwood. Mr. R. W. Estes (deceased) was also
very helpful.
Appreciation is expressed for the support and cooperation of
many well drilling contractors in the area. Mr. Ernest Hamilton,
Lake Monroe, was especially helpful and cooperative during the
investigation. Other drillers who helped by collecting rock cuttings
included the following: Mr. M. G. Hodges, Paola; Mr. H. C. Long,
Sanford; Mr. F. F. French, Longwood; the Libby and Freeman
Drilling Company, Orlando; and the Layne-Atlantic Company,
Orlando.
Dr. Herman Gunter, former director of the Florida Geological
Survey, and Dr. Robert Vernon, director of the Florida Geological
Survey, furnished much valuable information concerning the geology
of the county.
WELL-NUMBERING SYSTEM
The well-numbering system used in this report is based on latitude
and longitude coordinates. The well number was assigned by
first locating each well on a map that is divided into 1-minute
quadrangles of latitude and longitude, then numbering, consecutively,
each inventoried well in a quadrangle. The well number is a
composite of three numbers separated by hyphens: The first number
is composed of the last digit of the degree and the two digits of
the minute of the meridian of latitude on the south side of a 1-minute
quadrangle; the second number is composed of the last digit of the
degree and the two digits of the minute of the parallel of longitude
on the east side of a 1-minute quadrangle; and the third number
gives the order in which the well was inventoried in the 1-minute
quadrangle. For example, well number 844-114-1 was the first well
inventoried in the 1-minute quadrangle north of 28044' parallel of
latitude and west of the 81014' meridian of longitude. Wells re-
ferred to in the text can be located on figure 10 by this system.
Complete well descriptions, locations, and other data are to be
published as Florida Geological Survey Information Circular No. 34,
and may be obtained for $1.00 per copy.
GEOGRAPHY
TOPOGRAPHY AND DRAINAGE
The topography of Seminole County may be divided into two







REPORT OF INVESTIGATIONS No. 27


types: a flat lowland, characteristic of the area adjacent to Lake
Monroe; and hilly uplands, characteristic of the area in the vicinity
of Lake Mary.
The level lowland includes the area ranging from a few hundred
feet to more than 2 miles wide adjacent to the Wekiva, St. Johns,
and Econlockhatchee rivers and Lake Jessup. The land-surface
altitude within this area ranges from about 5 feet above mean sea
level near the St. Johns River to about 30 feet above sea level where
the lowland area merges into the hilly upland.
The hilly upland includes the remainder of the county. The
surface features of this area include many sandhills and lakes and
some level areas. Many of the lakes probably were formed by the
collapse of the surface sand and clay into caverns formed by the
solution and removal of the underlying limestone by circulating ground
water. The land surface in this area ranges from about 30 feet
above sea level where the area adjoins the level lowlands to about
105 feet above sea level in the vicinity of Altamonte Springs.
The level lowlands and small areas of the hilly uplands are
drained by the St. Johns River and its tributaries, which include
Lake Jessup, the Wekiva River, and the Econlockhatchee River. The
remainder of the hilly uplands drains into closed depressions. Many
of these depressions are probably drained through permeable material
into the underlying limestone aquifers.
CLIMATE
The climate of Seminole County is subtropical. The average annual
precipitation at Sanford for the 49 years of record (1883-87 and
1913-56) is 52.89 inches, according to the records of the U. S.
Weather Bureau. The maximum annual precipitation was 74.06 inches
in 1953, and the minimum annual precipitation was 35.54 inches in
1938. The monthly distribution of rainfall at Sanford and the maximum
and minimum rainfall of record are shown in figure 2. About 70
percent of the precipitation falls during the months of May through
October.
Temperature records at Sanford have been collected by the
weather bureau for 43 years. The mean annual temperature at
Sanford is 72.20F. The lowest mean monthly temperature is 61.4F. in
January; the highest mean monthly temperature is 82.20F. in August.
The average growing season is about 330 days.
POPULATION AND DEVELOPMENT
The 1950 census listed the population of Seminole County as
26,883. Sanford, the largest town and the county seat, had a population






FLORIDA GEOLOGICAL SURVEY


EXPLANATION


Maximum rainfall
(1913 1956)
14-
Average rainfall
(1913 1956)
12-
Minimum rainfall
(1913 1956)


10

8

6

4

2

0


r


7


7
?X


I


/


r


JAN FEB MAR APR MAY JUNE JULY AUG SE OCT NOV DEC
Figure 2. Monthly distribution of rainfall at Sanford.


-1^-^-


77i~







REPORT OF INVESTIGATIONS NO. 27


of 11,935. The populations of the largest towns were as follows:
Oviedo, 1,601; Altamonte Springs, 858; Longwood, 717; and Lake
Mary, about 800.
Sanford is at the site of Camp Monroe, which was established in
1836 by -troops of the U. S. Army to protect the settlers from the
Seminole Indians. Fort Mellon, a more permanent base named to
honor Captain Charles Mellon, soon replaced Camp Monroe. In 1870,
General Henry S. Sanford purchased 12,535 acres of land west of
Fort Mellon and laid out the town named for him. Sanford was
incorporated in 1877 and included Fort Mellon.
Orange groves were set out in about 1840 and served as a main
source of income. Other crops were grown until the "big freeze" of
1895 blackened most of the agriculture of the State. This freeze caused
the settlers to depend on other crops because it was several years
before the citrus trees would again bear fruit. Shortly after the "big
freeze," a method of subirrigation of crops was developed for use in
the level lowlands. This method of irrigation enabled the area to
maintain an agricultural economy balanced between citrus crops and
winter vegetables According to the Florida State Marketing Bureau's
annual fruit and vegetable report for the 1952-53 season (Scruggs
and Scar rough, 1953), Seminole County had a total of 8,575 acres
under cultivation and an additional 7,829 acres planted in citrus groves.

GEOLOGY
STRATIGRAPHY
The only geologic units exposed in Seminole County are deposits
of Pleistocene and Recent Age, which cover the entire county. Infor-
mation about the subsurface geology in the county was obtained from
well cuttings from 69 wells, well logs studied by Sidney A. Stubbs
in the late thirties, and well logs from surrounding counties. Most of
the cuttings from the 69 wells were collected during this investigation
and the remainder were obtained from the files of the Florida
Geological Survey, Tallahassee, Florida.
The geologic formations and .their water-bearing properties are
described in detail in the following pages and described briefly in
table 1. Two cross sections showing the formations penetrated by water
wells are given in figure 3.
PRE-MESOZOIC ROCKS
The top of the pre-Mesozoic rocks in Seminole County is given by
Applin (1951, fig. 2) as about 6,000 feet below sea level. Applin has
classified these crystalline rocks as granite, diorite, and metamorphic







FLORIDA GEOLOGICAL SURVEY


Thanks are extended to others in the county who have been especially
helpful. These men include: Mr. C. S. Lee, Oviedo; Dr. Phillip Westgate,
Central Florida Experiment Station, Sanford; Mr. Benjamin Wiggins, Soil
Conservation Service, Sanford; Mr. Randall Chase, Sanford; and Mr.
LeRoy Hennessey, Longwood. Mr. R. W. Estes (deceased) was also
very helpful.
Appreciation is expressed for the support and cooperation of
many well drilling contractors in the area. Mr. Ernest Hamilton,
Lake Monroe, was especially helpful and cooperative during the
investigation. Other drillers who helped by collecting rock cuttings
included the following: Mr. M. G. Hodges, Paola; Mr. H. C. Long,
Sanford; Mr. F. F. French, Longwood; the Libby and Freeman
Drilling Company, Orlando; and the Layne-Atlantic Company,
Orlando.
Dr. Herman Gunter, former director of the Florida Geological
Survey, and Dr. Robert Vernon, director of the Florida Geological
Survey, furnished much valuable information concerning the geology
of the county.
WELL-NUMBERING SYSTEM
The well-numbering system used in this report is based on latitude
and longitude coordinates. The well number was assigned by
first locating each well on a map that is divided into 1-minute
quadrangles of latitude and longitude, then numbering, consecutively,
each inventoried well in a quadrangle. The well number is a
composite of three numbers separated by hyphens: The first number
is composed of the last digit of the degree and the two digits of
the minute of the meridian of latitude on the south side of a 1-minute
quadrangle; the second number is composed of the last digit of the
degree and the two digits of the minute of the parallel of longitude
on the east side of a 1-minute quadrangle; and the third number
gives the order in which the well was inventoried in the 1-minute
quadrangle. For example, well number 844-114-1 was the first well
inventoried in the 1-minute quadrangle north of 28044' parallel of
latitude and west of the 81014' meridian of longitude. Wells re-
ferred to in the text can be located on figure 10 by this system.
Complete well descriptions, locations, and other data are to be
published as Florida Geological Survey Information Circular No. 34,
and may be obtained for $1.00 per copy.
GEOGRAPHY
TOPOGRAPHY AND DRAINAGE
The topography of Seminole County may be divided into two











'I14ULI 1 8o.ol UnIts II 801I1ol4)I County


Age


Unit


Pleistocene and Recent. .. .. Undlfferentiated deposits,...



Late Miocene or I'loceno. Undifforentiated deposits, ,..


Miocene ............... Hawthorn Formation .......


Eocene ................ .. Ocala Group ................


Eocene ............ ..,,. I Avon Park Limnetono, ......


Eocene . .. .. ... Lake City .... ........


Thicknuies
(feet)


10- 75



0- 83


0-150



0-190





500 --





Over 400


Physical Charactur


Said, u0ntaining some shells and clay..



Sticky blue clay and shell beds., .....


Blue to gray calcareous clay; cream to
gray sandy limestone' containing
grains of cream to black phosphate
rook and fragments of chert,, .. .. ,, .
Cream to tan-gray, soft to hard, gran-
ular, porous foraminiferal marine
limestone .......................



Light-gray to brown, soft to hard, por.
ous to dense, granular to chalky
limestone and dolomitic limestone ,,




Hard, brown porous, crystalline dolo-
mite; hard, cream to tan chalky
limestone and dolomitic limestone...


,.,_,,~_..,.,- .-.,-,,~-~,~,__. _...-,,,.,_,1.,.~,,,., -.I,


Wator-Ilearing Character

Furnishes water to shallow wells equipped with
screens. Usually adequate for lawn irrigation,
domestic and stock use. The water Is softer
and more corrosive than water from the Mio-
cone and Eocene deposits,
The shell beds yield small to moderate quantities
of water to wells. Water from wells that tap
these beds flow in most of the lower lands. The
clay beds confine water under artesian pressure,
The beds of sandy limestone yield substantial
nuantities of water to wells drilled for Irriga.
tion or domestic uses. The clay beds serve as
an aqulolude.
The second most productive formation in the
county. The Ooala furnishes large quantities of
water to many wells which tap it only and
contributes considerable water to wells that
tap both overlying or underlying formations
also. It is the first limestone penetrated in most
of the county.
The most productive' formation in Seminule
County. Yields water to all the deeper wells in
the county and is the only part of the Floridan
aquifer tapped by many wells. Very few wells
draw water from the lower part of the Avon
Park and very substantial additional supplies
could be developed from that part of the for-
mation.
A highly productive formation in the southwest-
ern part of the county but tapped by only a
few wells. No information is available about
the hydraulic properties or the chemical qual-
ity of the water from this formation elsewhere
in the county.



































Figure 3. Geologic units penetrated by water wells in Seminole County.







REPORT OF INVESTIGATIONS NO. 27


of 11,935. The populations of the largest towns were as follows:
Oviedo, 1,601; Altamonte Springs, 858; Longwood, 717; and Lake
Mary, about 800.
Sanford is at the site of Camp Monroe, which was established in
1836 by -troops of the U. S. Army to protect the settlers from the
Seminole Indians. Fort Mellon, a more permanent base named to
honor Captain Charles Mellon, soon replaced Camp Monroe. In 1870,
General Henry S. Sanford purchased 12,535 acres of land west of
Fort Mellon and laid out the town named for him. Sanford was
incorporated in 1877 and included Fort Mellon.
Orange groves were set out in about 1840 and served as a main
source of income. Other crops were grown until the "big freeze" of
1895 blackened most of the agriculture of the State. This freeze caused
the settlers to depend on other crops because it was several years
before the citrus trees would again bear fruit. Shortly after the "big
freeze," a method of subirrigation of crops was developed for use in
the level lowlands. This method of irrigation enabled the area to
maintain an agricultural economy balanced between citrus crops and
winter vegetables According to the Florida State Marketing Bureau's
annual fruit and vegetable report for the 1952-53 season (Scruggs
and Scar rough, 1953), Seminole County had a total of 8,575 acres
under cultivation and an additional 7,829 acres planted in citrus groves.

GEOLOGY
STRATIGRAPHY
The only geologic units exposed in Seminole County are deposits
of Pleistocene and Recent Age, which cover the entire county. Infor-
mation about the subsurface geology in the county was obtained from
well cuttings from 69 wells, well logs studied by Sidney A. Stubbs
in the late thirties, and well logs from surrounding counties. Most of
the cuttings from the 69 wells were collected during this investigation
and the remainder were obtained from the files of the Florida
Geological Survey, Tallahassee, Florida.
The geologic formations and .their water-bearing properties are
described in detail in the following pages and described briefly in
table 1. Two cross sections showing the formations penetrated by water
wells are given in figure 3.
PRE-MESOZOIC ROCKS
The top of the pre-Mesozoic rocks in Seminole County is given by
Applin (1951, fig. 2) as about 6,000 feet below sea level. Applin has
classified these crystalline rocks as granite, diorite, and metamorphic






FLORIDA GEOLOGICAL SURVEY


rocks. They have been termed basement rocks in some publications on
the Florida Peninsula. The depth to the crystalline rocks was deter-
mined from oil test wells in Volusia, Lake, and Osceola counties. The
formations that overlie these crystalline rocks consist of shallow-water
marine deposits, most of which are limestone.
EOCENE SERIES
The upper part of the Eocene Series in Seminole County consist of
the Lake City Limestone, the Avon Park Limestone, and the Ocala
Group (fig. 3, 4).
Figure 4 shows contours in altitude in feet below sea level of the
top of the Eocene limestones in Seminole County. The amount of casing
required to case a well to the uppermost limestone formation can be
determined approximately from this map if the land-surface elevation is
known. The upper surface of the Eocene Limestone ranges from 75 to
about 190 feet below the land surface.
Lake City Limestone
Name: The name Lake City Limestone was given by Applin and
Applin (1944, p. 1680) to a limestone of Claiborne (middle Eocene)
Age penetrated in a well at Lake City, Florida.
Lithology: The Lake City Limestone consists of alternating layers of
hard, brown, porous crystalline dolomite and hard, cream to tan chalky
limestone and dolomitic limestone.
Distribution and thickness: Cooke (1945, p. 45-46) states that the
Lake City Limestone underlies all of Florida except the northwestern
part, where the limestone grades laterally into a plastic facies related
to the Cook Mountain Formation of Claiborne Age.
According to Applin and Applin (1944), the Lake City Limestone
ranges in thickness from 400 to 500 feet in the northern part of Florida
and from 200 to 250 feet in the southern part. The Lake City is more
than 400 feet thick in the southwestern part of Seminole County.
Stratigraphic relations: In most of the Florida Peninsula, the Lake
City Limestone unconformably overlies the Oldsmar Limestone. In Sem-
inole County, the Lake City is overlain by the Avon Park Limestone. In
the southwestern part of Seminole County, the top of the Lake City Lime-
stone was penetrated about 600 feet below sea level in well 839-125-2
(fig. 3).
Water-bearing characteristics: The Lake City Limestone is the oldest
formation penetrated by water wells in Seminole County. Only a few wells
have been drilled into this formation because adequate supplies of water
can generally be obtained from the overlying deposits, although the Lake






REPORT OF INVESTIGATIONS No. 27


City Limestone appears to be highly productive in Seminole County.
The largest yield pumped from a well in Seminole County was reported
to be 8,100 gpm (gallons per minute) and this was obtained from a well
that penetrates more than 400 feet of Lake City Limestone and less than
200 feet of Avon Park Limestone.
Water from the Lake City is somewhat less mineralized than water
from the overlying formations in the southwestern part of Seminole
County and northern Orange County. This is probably not true where
the overlying formations contain salt water. The good quality of the
water from the Lake City Limestone may be due to the fact that the
formation contains a considerable percentage of dolomite or dolomitic
limestone which is less soluble in water than is limestone. No informa-
tion is available concerning the chemical quality of the water in this
formation in any area where the overlying formations contain salty
water.
The Lake City Limestone could become an important aquifer in some
areas of Seminole County if large quantities of ground water are required.
In order to fully appraise the Lake City Limestone as an aquifer, it
would be necessary to drill several wells into the formation in different
parts of the county. The hydraulic properties of the formation and the
chemical quality of the water could then be determined.
Avon Park Limestone
Name: The name Avon Park Limestone was given by Applin and
Applin (1944, p. 1680) to a limestone of Claiborne (middle Eocene) Age
penetrated in a well at the Avon Park Bombing Range in Polk County,
Florida.
Lithology: The Avon Park Limestone consists of layers of light gray
to brown, soft to hard, porous to dense, granular to chalky limestone.
The formation has been irregularly dolomitized since deposition, but the
original structures of the rock generally have been preserved.
Distribution and thickness: The Avon Park Limestone underlies most
of the Florida Peninsula. It is exposed in parts of Citrus and Levy counties
and is the oldest formation that crops out in Florida.
According to Applin and Applin (1944), the thickness of the Avon
Park Limestone ranges from 50 feet or less in northeast Florida to 650
feet in the southern part of the Florida Peninsula. In the southwestern part
of Seminole County, the Avon Park Limestone is more than 500 feet thick.
Stratigraphic relations: The Avon Park Limestone rests -conformably
upon the Lake City Limestone. In Seminole County, the Avon Park is
unconformably overlain by the Ocala Group except where the Ocala is






FLORIDA GEOLOGICAL SURVEY


absent in the north-central part of the county. Here the Avon Park is
overlain by the Hawthorn Formation or younger deposits.
Structure: Subsurface contours on the top of the Avon Park Limestone
are shown in figure 5. This figure shows the top of the Avon Park Lime-
stone to be 27 to about 100 feet below sea level in the area around
Sanford and about 250 feet below sea level in the southeastern part of
the county. The eroded surface of the Avon Park Limestone slopes south-
southeast about 25 feet per mile in the area from Lake Jessup south and
southeast toward Orange County. West of Sanford the surface of the Avon
Park slopes west, toward the Wekiva River, about 20 feet to the mile.
Water-bearing characteristics: The Avon Park Limestone yields more
ground water in Seminole County than any other formation. This is due
principally to its wide areal extent, thickness, and high permeability.
The Avon Park is the shallowest limestone formation that underlies all
of Seminole County, and supplies water to most of the deeper wells. The
large amount of water obtained from this limestone demonstrates its high
permeability. Well 840-107-2, 2.1 miles north of Chuluota, flows about
350 gpm from the Avon Park (fig. 24).
Most of the existing wells penetrate only the upper part of the Avon
Park Limestone; however, the lower part of the formation could become
important if even larger quantities of water are needed.

Ocala Group
Name: The Ocala Limestone was named for limestone outcrops near
Ocala, Marion County, by Dall and Harris (1892, p. 103), who believed
that it was Eocene or Oligocene in age. Cooke (1926, p. 251-297) con-
cluded that the limestone was of Jackson Age (late Eocene). Cooke and
Mossom (1929, p. 47-48) defined the name Ocala as including all rocks
of Eocene Age exposed in Florida. Applin and Applin (1944, p. 1683-
1684) stated that it was possible to separate the Ocala Limestone into
an upper and lower member, and listed some characteristic Foraminifera.
On the basis of differences in lithology and fossil content of the Ocala
Limestone, Vernon (1951, p. 156-171) restricted the name Ocala Lime-
stone to the upper part and named the lower part the Moodys Branch
Formation. He further subdivided the Moodys Branch Formation into the
Williston Member at the top and the Inglis Member at the bottom.
Recently, Puri (1953, p. 130) changed the name of the Ocala Limestone
(restricted) to Crystal River Formation and raised the Williston and
Ingis members of the Moodys Branch to the rank of formations. These
three formations, the Crystal River, Williston, and Inglis, are now collec-
tively referred to as the Ocala Group by the Florida Geological Survey.






REPORT OF INVESTIGATION NO. 27


Lithology: The Ocala Group consists of white-cream to tan-gray soft
to hard, granular, porous foraminiferal marine limestones. In most places
the Crystal River Formation is white to cream and parts of it are com-
posed almost entirely of remains of large foraminifers. The Williston and
Inglis Formations generally are harder, more granular and contain fewer
large Foraminifera than the overlying Crystal River.
Distribution and thickness: The Ocala Group underlies most of Flor-
ida except the east-central part of the peninsula (Applin and Applin,
1944, p. 1685). It is thin or missing in the northern part and in a small
area in the southwestern part of Seminole County. The thickness of the
Ocala Group ranges generally from 0 to 190 feet. Vernon (1951, p. 57)
states that the Ocala Group has been thinned by erosion along the flanks
of a structural high near Sanford and removed from the crest of the
high. The Sanford high is described by Vernon (1951, p. 57) as the up-
thrown side of a closed fold that has been faulted.
Stratigraphic relations: The Ocala Group lies unconformably on the
Avon Park Limestone in the Florida Peninsula, and is overlain uncon-
formably by the Hawthorn Formation. In places in the northern part of
the county where the Ocala Group is present and the Hawthorn is absent,
the Ocala is overlain unconformably by deposits of Pliocene or late
Miocene Age.
Structure: The altitude of the top of the Ocala Group ranges from
near sea level near the town of Lake Mary to about 113 feet below sea
level near the village of Lake Monroe.
Water-bearing characteristics: The Ocala Group is a very productive
part of the Floridan aquifer and next to the Avon Park Limestone is the
most productive source of ground water in Seminole County. Hundreds
of wells in the county tap only the Ocala Group. Wells penetrating the
Ocala yield from a few gallons per minute to more than 500 gpm. Figure
27 shows that well 838-113-3, 2.5 miles southeast of Oviedo, flows 170
gpm from the Ocala. The Ocala yields about 200 gpm to well 842-111-6,
2.3 miles northeast of Oviedo, as illustrated in figure 28.
MIOCENE SERIES
Hawthorn Formation
Name: The name Hawthorn Formation was first applied by Dall and
Harris (1892, p. 107) to rocks of early and middle Miocene Age that are
exposed near Hawthorn in Alachua County, Florida.
Lithology: The Hawthorn Formation in Seminole County consists of
beds of blue to gray, calcareous clay, alternating with beds of cream
to gray sandy limestone containing numerous grains of black to cream
phosphate rock and fragments of chert.






FLORIDA GEOLOGICAL SURVEY


Distribution and thickness: The Hawthorn Formation apparently un-
derlies the entire Florida Peninsula except in parts of the Ocala uplift
and the Sanford high, where it has been eroded. It is present throughout
Seminole County except in the northern part, along the St. Johns River,
where it has been removed by erosion.
According to Bishop (1956, p. 27), the Hawthorn Formation has a
maximum thickness of 650 feet in Highlands County, Florida. Cooke
(1945, p. 145) states that the Hawthorn is about 400 feet thick in Nas-
sau County, Florida. In Seminole County, the maximum observed thick-
ness of the Hawthorn Formation was 150 feet in a well at the south-
western part of the county.
Stratigraphic relations: The Hawthorn Formation unconformably
overlies the Ocala Group in most places. Where the Ocala is absent, the
Hawthorn rests unconformly upon the Avon Park Limestone. The Haw-
thorn Formation is unconformably overlain by deposits of Pliocene or
late Miocene Age or by deposits of Pleistocene Age. The study of well
cuttings in Seminole County has not revealed any rocks representing the
time interval between the Ocala Group and the Hawthorn Formation.
Water-bearing characteristics: The beds of sandy limestone in the
Hawthorn Formation yield substantial quantities of water to some wells
and are an important source of water for domestic and irrigation supplies.
Well 842-111-6, 2.3 miles northeast of Oviedo (fig. 28), obtains at least
500 gpm of water from the Hawthorn Formation. However, the Haw-
thorn Formation includes clay beds of low permeability, which confine
the water in the underlying limestones.
PLIOCENE OR UPPER MIOCENE DEPOSITS
Name: The beds of Pliocene Age exposed along the Caloosahatchee
River in the vicinity of La Belle, Hendry County, Florida, were first
recognized by Heilprin (1887). Dall (1887) described them as the
Caloosahatchie beds. Matson and Clapp (1909) used the term Caloosa-
hatchee marl for the deposits of Pliocene Age in the vicinity of the
Caloosahatchee River but proposed the term Nashua Marl for the depos-
its of Pliocene Age they found in the valley of the St. Johns River. Cooke
and Mossom (1929, p. 152) included the Nashua in the Caloosahatchee
Marl.
Vernon (1951, fig. 13, 33) considered the Caloosahatchee Marl to
be of late Miocene Age. As the correct age of these deposits has not been
determined, they are referred to in this report as Pliocene or upper
Miocene deposits.
Lithology: The Pliocene or upper Miocene deposits consist of sticky
blue clay and shell beds.






REPORT OF INVESTIGATIONS No. 27


Distribution and thickness: The deposits of Pliocene or late Miocene
Age are found in wells in the northern part of Seminole County, especially
along the St. Johns River valley, but do not crop out in Seminole County.
Stubbs (1987, p. 30) gives the maximum measured thickness of the
Pliocene or upper Miocene deposits as about 70 feet in the St. Johns River
valley, although he states that they may be thicker. Information from
well cuttings examined during the present study shows the maximum
thickness of these beds to be 83 feet.
Stratigraphic relations: The Pliocene or upper Miocene deposits lie
unconformably upon the Hawthorn Formation where it is present, and
upon the limestones of Eocene Age where the Hawthorn is absent. The
Pliocene or upper Miocene deposits are overlain unconformably by
deposits of Pleistocene Age.
Water-bearing characteristics: The shell beds yield small to moderate
quantities of water to wells. Of the wells .that penetrate the shell beds,
some draw entirely from them, but most also are open to the underlying
limestone and obtain water from both sources.
PLEISTOCENE AND RECENT DEPOSITS
Lithology: The Pleistocene and Recent deposits in Seminole County
consist of clear to frosted, fine to coarse quartz sand. In areas near the
St. Johns River, the deposits also include some shells and thin beds of
clay. Beneath the level lowlands of Seminole County, thin layers of hard-
pan have been formed at a depth of 3 to 5 feet through cementation
of sand by iron oxide.
Distribution and thickness: The Pleistocene and Recent deposits
mantle the entire county. They range in thickness from 10 to 75 feet.
Stratigraphic relations: In Seminole County, the Pleistocene and Re-
cent deposits rest unconformably upon deposits of Pliocene or late Mio-
cene Age, and upon the Hawthorn Formation where the beds of Pliocene
or late Miocene Age are absent.
Water-bearing characteristics: The Pleistocene and Recent deposits
furnish water to shallow driven wells that are equipped with screens.
The deposits will yield sufficient quantities of water to most wells for
domestic use and lawn irrigation. Most of the wells screened in these
deposits yield soft water that is more acid than water from the limestone
formations. The water from many of the wells contains objectionable
amounts of iron.
STRUCTURE
The contours in figure 4 show the configuration of the surface of
the limestones of Eocene Age. The contours represent the surface of






FLORIDA GEOLOGICAL SURVEY


ihe Avon Park Limestone in the Sanford area and in an area south of
AItamonte Springs where post-Eocene erosion removed all the
Ocala Group. In the remainder of Seminole County, the contours
represent the surface of the Ocala Group. This surface (fig. 4) has
many irregularities because it has been eroded and because many
sinkholes exist in the area. Some geologic evidence suggests that several
of the irregularities actually may be faults.
Geologic data in Seminole and Volusia counties (Wyrick, 1960)
suggest the presence of a downthrown fault block along the north edge
of Seminole County and south edge of Volusia County. This fault
block underlies part of the St. Johns River valley and most of Lake
Monroe. A surface expression of this fault block is probably shown by
the westerly offset of the St. Johns River along the northern part of
the county. The upper part of the St. Johns River generally flows
north-northwest until it reaches the northeast corner of Seminole
County. The river turns at that point and flows in a westerly direction
for about 18 miles. Then the river turns and continues in the original
northerly direction.

GROUND WATER
Ground water is the subsurface water in the zone of saturation,
the zone in which all pore spaces are filled with water under
pressure greater than atmospheric. Ground water is derived almost
entirely from precipitation. Part of the precipitation returns to the
atmosphere by evaporation and the transpiration of plants and part
drains from the land surface into lakes and streams; the remainder seeps
into the soil zone where some is retained and some continues downward
to the zone of saturation to become ground water. Ground water moves
laterally, under the influence of gravity, toward places of discharge such
as wells, springs, surface streams, lakes, or the ocean.
Ground water may occur under either nonartesian or artesian
conditions. Where it is not confined its upper surface, the water table,
is free to rise and fall and it is said to be under nonartesian or
water-table conditions. Where the water is confined in a permeable
bed that is overlain by a less permeable bed, so that its upper sur-
face is not free to rise and fall, it is said to be under artesian conditions.
The term "artesian" is applied to ground water that is confined
under sufficient pressure to rise in wells above the top of the
permeable bed that contains it, though not necessarily to or above
the land surface. The height to which water will rise in an artesian
well is called the artesian pressure head. The piezometric surface is
an imaginary surface to which water from an artesian aquifer will






REPORT OF INVESTIGATIONS No. 27


rise in tightly cased wells that penetrate the aquifer. Where the
piezometric surface is above the land surface, artesian wells will
flow under natural pressure.
An aquifer is a formation, group of formations, or part of a
formation-in the zone of saturation-that is permeable enough to
transmit usable quantities of water to wells. Areas in which water
enters the aquifers are called recharge areas and areas in which
water is lost from aquifers are called discharge areas.

NONARTESIAN AQUIFER
Ground water in Seminole County occurs under either non-
artesian or artesian conditions. The water in the surficial sands of
Pleistocene and Recent Age is under nonartesian conditions in all
parts of the county except a few small areas where the sands are
overlain by thick beds of peat or clay.
Wells drawing water from these sands are used mainly for domestic
supplies, although many of these wells are used for lawn and garden
irrigation. Generally, these wells are equipped with hand pumps,
but many of the hand pumps are being replaced with electric pumps.
Probably not more than 400 wells draw water from the sands of
Pleistocene and Recent Age in Seminole County.
The nonartesian aquifer is replenished by local precipitation. In
addition to this recharge, some of the water discharged from the
aquifer by pumping is returned to the aquifer by downward infiltration
of irrigation water. Water is lost from the aquifer by natural discharge
through springs into lakes and streams, by downward percolation into
the artesian aquifer in areas where the piezometric surface is below
the water table, and by withdrawal from wells. Water from the
aquifer generally contains about 50 ppm of dissolved solids in those
areas where the water in the aquifer has not been contaminated by
highly mineralized artesian water. In many areas of the county, water
from the nonartesian aquifer contains an excessive amount of iron,
which can stain clothes, fixtures, and utensils.

ARTESIAN AQUIFER
The principal sources of water in Seminole County are deposits
that form a part of the principal artesian aquifer of the Florida
Peninsula and adjacent area. This aquifer in Seminole County is
composed of beds of sand and shell in the lower part of the deposits
of Pliocene and late Miocene Age, the permeable parts of the Hawthorn
Formation, and limestone formations of middle and late Eocene Age.






FLORIDA GEOLOGICAL SURVEY


Stringfield (1936) first described the principal artesian aquifer
in Florida. The name Floridan aquifer, which will be used in this
report, was proposed by Parker (Parker, et al., 1955, p. 188-189) to
include "parts or all of the middle Eocene (Avon Park and Lake
City limestones), upper Eocene (Ocala Limestone), Oligocene
(Suwannee Limestone), and Miocene (Tampa Limestone, and per-
meable parts of the Hawthorn Formation that are in hydrologic
contact with the rest of the aquifer)." The artesian water is confined
by relatively impermeable layers in the limestones and by the
overlying clay of Miocene Age which extends over most of the State.
Differences in static head, chloride content, and temperatures of water
at different depths in some parts of Seminole County suggest that
relatively impermeable beds may be continuous over large areas,
and that the Eocene limestones consist of several relatively thin
aquifers rather than one thick aquifer.
The height to which water will rise in an artesian well is called
the artesian pressure head. The head at any place in the artesian
aquifer is controlled in part by the head in the recharge area, which
in turn is determined by the amount of replenishment that reaches
the aquifer from rainfall. Periodic measurements of the pressure head
and the water levels in wells are an important part of a ground-water
investigation. Stringfield (1936, p. 195) made a series of water-level
measurements in selected wells in Seminole County. In 1937, Stubbs
resumed measurements in several of the wells measured by Stringfield.
and also began measurements in other selected wells (S. A. Stubbs
and Irving Feinberg, unpublished records in the files of H. James Gut,
Sanford, Florida). Stubbs (1937, p. 33) stated that the minimum
permanent loss of head within the flowing-well area ranged from 4
to 10 feet during the period 1912-37. During the current investigation
measurements were resumed in many of the wells measured by
Stringfield and Stubbs, to determine if there had been any progressive
decline of artesian head. In addition, periodic measurements were
made in 40 other wells to determine the seasonal fluctuations of the
water level in different parts of the county.
PIEZOMETRIC SURFACE IN FLORIDA
The piezometric surface of the Floridan aquifer in Florida is
shown by the contour lines in figure 6. The first map of the piezometric
surface of the principal artesian aquifer in Florida was compiled
by Stringfield (1936, pI. 12). The contours on the piezometric surface
indicate the direction of movement of the artesian water. Water enters
the aquifer in the areas in which the piezometric surface is high and










REPORT OF INVESTIGATIONS No. 27


Figure 6. The piezometric surface of the Floridan aquifer, 1949.
moves in a direction approximately perpendicular to the contour lines
toward the areas in which the piezometric surface is low. One of the
most notable features of the piezometric surface in Florida is the dome
centered in Polk County, which indicates that considerable recharge
enters the Floridan aquifer in Polk County and some surrounding
counties.
In Polk County, the western part of Orange County, and some
parts of Seminole County, water enters the Floridan aquifer through
numerous sinkholes that penetrate the Hawthorn and younger for-
mations. The contours on figure 6 show that the artesian water flows
northeast from the recharge area centered in Polk County toward
Seminole County and the adjacent area. This map shows the principal
recharge areas for the Floridan aquifer, but the map is not detailed
enough to show the many small recharge areas that are known to
exist.


95 0. -t W .7 100 MeS I
0oproaUme Scott






FLORIDA GEOLOGICAL SURVEY


PIEZOMETRIC SURFACE IN SEMINOLE COUNTY
The first published maps of the piezometric surface in Seminole
County (Stubbs, 1937, p. 25-26) show in considerable detail the
direction of ground-water flow in the county. Maps of the piezometric
surface drawn during the current investigation generally agree with
those drawn by Stubbs. One difference occurs in the area northeast of
Oviedo where Stubbs' map shows a recharge area in an area of
flowing wells. This discrepancy is believed to be due to an error in
leveling by Stubbs or to using an incorrect benchmark elevation.
Figure 7 shows the piezometric surface of the Floridan aquifer
in Seminole County during near record-high water levels in January
1954. The annual rainfall at Sanford in 1953 was 74.06 inches, which
is the highest on record. Most of this rain, or 51.60 inches, fell during
the period July 1 to December 31, 1953. The maximum artesian
pressure measured in January 1954 was 66 feet above sea level in a
well 6 miles southwest of Oviedo and the minimum pressure measured
was 11 feet above sea level in a well 6 miles north of Geneva in the
St. Johns River valley.
The piezometric map shows that in general the flow of water in
the county is toward the northeast. The effect of ground-water dis-
charge near Sanlando Springs, and in areas 2 miles south of Lake
Mary and 2 miles northeast of Oviedo is shown by depressions in the
piezometric surface (fig. 7). The effect of ground-water recharge in
the areas near Geneva, south of Oviedo, near Chuluota, south of
Sanford, and south of Paola is shown by mounds in the piezometric
surface (fig. 7). The contours also indicate discharge into the St.
Johns and Wekiva rivers and into the southwest part of Lake Jessup.
Figure 8 shows the piezometric surface of the Floridan aquifer at
near record-low conditions in June 1956. The total rainfall at Sanford
was only 16.45 inches for the 8-month period from October 1, 1955
to May 31, 1956. The difference in artesian pressure from the high
level shown on figure 7 to the low level shown on figure 8 is
generally about 5 feet, although one well showed a decline of 10 feet.
Figure 8 shows a piezometric high near Golden and Silver lakes,
:3J. miles south of Sanford, which indicates that this is a recharge area.
The highest water level measured in Seminole County during June
1956 was 53 feet above sea level in two wells located near Altamonte
Springs. The lowest water level measured during this dry period was
7 feet above sea level in a well located 6 miles north of Geneva in the
St. Johns River valley. As figures 7 and 8 show approximately
the maximum and minimum conditions, respectively, the piezometric
surface would usually be somewhere between these two extremes.






REPORT OF INVESTIGATIONS No. 27


AREA OF ARTESIAN FLOW
Whenever the piezometric surface stands higher than the land
surface, artesian wells will flow. The approximate areas of artesian
flow in 1954 in Seminole County are shown in figure 9. The principal
area of flow extends in an unbroken band along the Wekiva River
to the St. Johns River and continues along the St. Johns River to
a point about 4 miles east of Lake Jessup. The band includes
both sides of Lake Jessup and the farming area southwest of Oviedo.
East of Oviedo the area of flow extends down the valley of the
Econlockhatchee River to the St. Johns River.
The area of artesian flow was probably larger prior to the agricul-
tural development of the county. In fact, in parts of the farming
area in the vicinity of Sanford, the boundary was probably more than
half a mile farther south than it was in 1956. In most of the farming
areas the boundary of the area of flow has receded onto the level
lowlands, where a decline in artesian pressure of 1 foot results in a
decrease of several hundred feet in the width of the area of flow.
Figure 9 shows also contours which represent the height, in feet,
referred to land surface, to which water will rise in artesian wells
penetrating the limestone aquifer. It shows that the maximum depth
to water is more than 50 feet below land surface in an area near
the southwest corner of the county and at Geneva. The artesian pres-
sure head is more than 20 feet above the land surface in an area
adjacent to the Little Wekiva River, the east edge of Lake Monroe,
and around most of Lake Jessup. Along Howell Creek, at the south
side of Lake Jessup, water from tightly cased wells drilled into the
limestone aquifer will rise more than 30 feet above the land surface.

WELLS
One important phase of any ground-water investigation is the
well inventory, or collection of data on wells. Figure 10 shows the
location and distribution of 874 wells, which were inventoried during
the investigation, and which represent 18 percent of the total number
of wells in the county. Of this number, 50 wells draw water from
the nonartesian aquifer and 824 wells, of which 424 flow, draw
water from the Floridan aquifer. The following table shows a division
of the wells according to their use.
The relative percentage of the wells of each diameter would probably
remain about the same if all the wells in the county were inventoried.
Table 3 shows that almost 47 percent of the inventoried wells are 2
inches in diameter.







FLORIDA GEOLOGICAL SURVEY


TABLE 2. Use of Inventoried Wells
Use of well Number
Domestic 322
Irrigation 312
Unused 137
Industrial and Public Supply 62
Stock 39
Other uses 2
Total 874
The following table shows a classification of the wells according to
their diameter.
TABLE 3. Diameter of Inventoried Wells.
Well diameter Number of Percent of
(inches) wells total
1Y 49 5.6
2 407 46.6
2Js 28 3.2
3 173 19.8
4 123 14.1
5 9 1.0
6 47 5.4
8 21 2.4
over 8 17 1.9
Total 874 100.0
Artesian wells in the county range in depth from 33 to 1,122 feet
but more than 90 percent of them are between 75 and 250 feet deep.
More than 4,500 wells are believed to draw water from the artesian
aquifer in Seminole County.
The relation between the height of the static head above the well
outlet and the yield of four wells in the Sanford farming area is shown
in figure 11. The measurements of yield in gallons per minute and'arte-
sian pressure in feet above sea level are shown as solid dots. Each graph
is drawn as a wedge to cover the variations in the accuracy of the meas-
urements.
The yield of a flowing well depends primarily upon the water-
transmitting capacity of the formations penetrated by the well, the friction
losses within the well, the thickness of aquifer penetrated by the well,
and the height of the static head. The yield of different wells may be
compared by using the specific capacity, which is the yield in. gallons
per minute per foot of drawdown. In flowing wells, the drawdown is
approximately equal to the height of the static head above the well out-
let Therefore, the approximate specific capacity of these wells may be
determined by dividing the yield of the wells in gallons per minute by
the static head in feet.






REPORT OF INVESTIGATIONS No. 27


Well 1849-117-1 **
2iri.diameter .






18

17

16- -

15
16 -- ///- -- -




14

13

12
//


10 -
Elevation of discharge )ipe

0 5 10 15 20 2!

25 1 I
Well 847-113-21
3ir diameter reduced /
t24 _iO meter /

23

levation of discharge pipe
oo I--- -- I -- I i


YIELD IN GALLONS


25 I
Well 848-113-1
2in. diameter.


23/

22

21 /

20 /


Elevation of di harge pipe
180 5 10 15 20 2


PER MINUTE


Figure 11. Relation between the static head and the yield of four flowing artesian
wells in the area around Sanford.


20 25


1


'-0 5 10 15






FLORIDA GEOLOGICAL SURVEY


The specific capacity of well 849-117-1 was only 1.7 gpm per
foot of drawdown and the yield of the well ranged from 14 to 21 gpm as
the artesian pressure increased 3.5 feet. Well 848-113-1 had a specific
capacity of 2.5 gpm per foot of drawdown and the yield of the well
ranged from 4.5 to 12.5 gpm as the artesian pressure increased 4 feet.
Well 845-113-10 had a specific capacity of 6.6 gpm per foot of drawdown
and the yield of the well ranged from 0.5 to 22 gpm as the artesian
pressure increased 3 feet. Well 847-113-21, which is a 3-inch well reduced
to a 2-inch outlet, had a specific capacity of 11.1 gpm per foot of draw-
down and the yield ranged from 0 to 20 gpm as the artesian pressure
increased 1.8 feet. The average specific capacity for the 2-inch wells for
which data were available is 3.9 gpm per foot of drawdown.
Figure 12 is similar to figure 11 as it shows data on the specific capa-
city of three wells, 2 inches in diameter, which are located northeast of
Oviedo and one well, 3 inches in diameter, which is located south of Lake
Harney. The three wells northeast of Oviedo had specific capacities of
5.5, 7.2, and 10.1 gpm per foot of drawdown. The average specific
capacity of the 2-inch wells was 7.6 gpm per foot of drawdown. The
-3-inch well, south of Lake Harney, had a specific capacity of 15.8
gptm per foot of drawdown, and the yield rose from 7 to 65 gpm as
the artesian pressure increased 3.1 feet.
The measurements of the yield of these selected wells show that
the wells in the Oviedo area have a higher specific capacity than the
wells in the Sanford area. The graphs show also the reduction in the
vield of a well with each foot reduction in the static head. Thus, when
the artesian pressure is lowered in an area of flowing wells by excessive
draft or by dry weather conditions, some wells cease to flow and all
wells vield less water.

SUBIRRIGATION
Subirrigation is the main method of irrigation used in Seminole County.
This method is made possible because of several factors including: rela-
tively level land, a layer of cemented sand (hardpan) from 3 to 5 feet
below the land surface, and a layer of sand above the hardpan which
absorbs and distributes the water.
Subirrigation is used to control the moisture in the soil so that the
plants will have adequate available water. An advantage to subirriga-
tion is that water in the soil can be effectively controlled so that soluble
fertilizers are not washed beyond the reach of the plants. Another ad-
vantage is that during periods of excessive rainfall the ditches used for
subirrigation can be used to drain the excess water from the ground and






FLORIDA GEOLOGICAL SURVEY


ihe Avon Park Limestone in the Sanford area and in an area south of
AItamonte Springs where post-Eocene erosion removed all the
Ocala Group. In the remainder of Seminole County, the contours
represent the surface of the Ocala Group. This surface (fig. 4) has
many irregularities because it has been eroded and because many
sinkholes exist in the area. Some geologic evidence suggests that several
of the irregularities actually may be faults.
Geologic data in Seminole and Volusia counties (Wyrick, 1960)
suggest the presence of a downthrown fault block along the north edge
of Seminole County and south edge of Volusia County. This fault
block underlies part of the St. Johns River valley and most of Lake
Monroe. A surface expression of this fault block is probably shown by
the westerly offset of the St. Johns River along the northern part of
the county. The upper part of the St. Johns River generally flows
north-northwest until it reaches the northeast corner of Seminole
County. The river turns at that point and flows in a westerly direction
for about 18 miles. Then the river turns and continues in the original
northerly direction.

GROUND WATER
Ground water is the subsurface water in the zone of saturation,
the zone in which all pore spaces are filled with water under
pressure greater than atmospheric. Ground water is derived almost
entirely from precipitation. Part of the precipitation returns to the
atmosphere by evaporation and the transpiration of plants and part
drains from the land surface into lakes and streams; the remainder seeps
into the soil zone where some is retained and some continues downward
to the zone of saturation to become ground water. Ground water moves
laterally, under the influence of gravity, toward places of discharge such
as wells, springs, surface streams, lakes, or the ocean.
Ground water may occur under either nonartesian or artesian
conditions. Where it is not confined its upper surface, the water table,
is free to rise and fall and it is said to be under nonartesian or
water-table conditions. Where the water is confined in a permeable
bed that is overlain by a less permeable bed, so that its upper sur-
face is not free to rise and fall, it is said to be under artesian conditions.
The term "artesian" is applied to ground water that is confined
under sufficient pressure to rise in wells above the top of the
permeable bed that contains it, though not necessarily to or above
the land surface. The height to which water will rise in an artesian
well is called the artesian pressure head. The piezometric surface is
an imaginary surface to which water from an artesian aquifer will















REPORT OF INVESTIGATIONS No. 27


Z ell 841-It11 t
l. diameter
27 -- -

26 --



24


-J /
22- -



<^ -- --6 -----
2 9

L / *



1J 7
IL 16 ---- --------

S'Elevotion of dischrge pi
S 10 20 30 40 50 6C


I
3 Well 841-110-1 /
21st diameter







26 I I
/o

27 t/ -- -- -

26 le on of discharge p pe
.. I ~~Ipe___


Well 143-183-4
in. diameter




II
Eleo Ion ot discharge pipe
0 O. 10 20 30 40 50 60 70 80 90


0 10 -20 30 40 50 60 0 10 20 30 40 50 u0 tfo uf
YIELD IN GALLONS PER MINUTE
Figure 12. Relation between the static head and the yield of four flowing artesian
wells in the eastern part of Seminole County.






FLORIDA GEOLOGICAL SURVEY


prevent waterlogging of the soil, which destroys some beneficial soil
bacteria and has other harmful effects.
The land is prepared for subirrigation by clearing and leveling. An
artesian well is drilled at the highest point, and the water from the well
flows into a concrete or terra cotta standpipe (supply pocket) that is
connected to a tile main. Lines of tile laterals 18 to 24 feet apart are
also connected to this tile main. A stop pocket is placed at the end
of each lateral, opposite the main. A short tile line connects this pocket
to an open drainage ditch or a large sewer tile which is used to drain
the water from the field. The level of the water in the field can be
controlled by the amount of water taken from the well, by plugging or
partially unplugging the heads of the laterals, or by controlling the
amount of water that is drained from the field. Additional information
on subirrigation can be obtained from the Agricultural Extension Service,
Gainesville, Florida. This method of irrigation uses very large quantities
of water.
WATER-LEVEL RECORDS
A total of more than 4,500 water-level measurements were made of
563 wells during the investigation. Most of these measurements and the
dates on which they were made are presented in table 1 of Florida
Geological Survey Information Circular no. 34.
Fluctuations of the water level are caused principally by pumping,
rainfall, and changes in atmospheric pressure. In order to obtain contin-
uous records of the changes in the artesian pressure head in Seminole
County, a water-level recorder was installed in 1952 on well 841-121-1,
about 1.25 miles west-southwest of Longwood, in an area of little ground-
water use. Another recorder was installed in 1952 on a flowing well
(well 847-113-6), about 2.8 miles southeast of Sanford, in an area of
extensive ground-water use.
Hydrographs for the two wells equipped with automatic water-level
recorders, and the monthly rainfall at Sanford, are shown in figure 13.
The most noticeable features on both hydrographs (fig. 13) are the high
water levels during the fall and winter of 1953 and the low water levels
during the spring of 1956. These features show near maximum and
minimum water-level conditions. The hydrographs of the two wells shown
in figure 13 correlate generally; however, after the high water levels
during the period of September to December 1953, the water level in
well 847-118-6 had reached the bottom of its sharp decline by the mid-
die of February 1954, but the water level in well 841-121-1 did not
reach a similar stage until the end of May. The hydrograph for well
847-113-6 shows more rapid fluctuations than the other hydrograph,








REPORT OF INVESTIGATIONS NO. 27


>48
_J
<47

z46

2 45

M44
' 27
I-

u 26
z


15
*z TOTAL= 47.62 TOTAL
O(W

-- 5

a-


TOTAL = 45.60 TOTAL= 53.05 TO


-119511 1952 I 1953 1954 I 1955 1956

Figure 13. Hydrographs of the daily high water levels in wells 841-121-1 and
847-113-6 and the monthly rainfall at Sanford.


SI I i.


'AL= 42.4f


4.06






FLORIDA GEOLOGICAL SURVEY


principally because of the large changes in the amount of ground water
used near well 847-113-6. Water levels in well 847-113-6 ranged from a
low of 19.58 feet above sea level to a high of 26.45 feet above sea level,
or a fluctuation of almost 7 feet. Water levels in well 841-121-1 ranged
from a low of 44.55 feet above sea level to a high of 52.49 feet above
sea level, or a fluctuation of almost 8 feet. These hydrographs show the
general trend of the water level during the period from 1951 through
1956, and they show also the relationship between rainfall and water
levels.
An important part of the investigation in Seminole County involved
comparison of current water levels with past water levels, to see if a
progressive decline in water levels had occurred. All the water-level
measurements were referred to mean sea level as a common datum for
comparison. When evaluating rainfall records to detect progressive
trends, it is essential to compare periods of similar rainfall. An inspection
of rainfall records at Sanford shows that the rainfall a few years prior to
1938 might be compared to the rainfall prior to 1955. Thus, the average
water levels on the hydrographs for the years 1937 and 1954 can be
compared. Most of the difference in water levels between these 2 years
can be attributed to factors other than rainfall differences.
Figure 14 shows the hydrographs of five wells and the monthly rain-
fall at Sanford. These hydrographs include measurements made in 1933
and 1935 by V. T. Stringfield, in 1937 by S. A. Stubbs, and in 1939 by
Irving Feinberg. Well 846-116-11 is 2.9 miles south of Sanford near the
north edge of Lake Ada and near the city of Sanford well field. The hydro-
graph shows a fluctuation of about 6 feet for the period of record. The
data on the graph show that the water level has probably declined about
1 or 2 feet since 1937. Some of this decline might be the result of an
increase in pumpage by the city of Sanford from an average of 0.67 mgd
(million gallons per day) in 1938 to an average of 1.54 mgd in 1956.
Well 844-117-2 is 4.9 miles southwest of Sanford, near Elder Spring.
This well shows water-level fluctuations similar to those of well 846-116-
II. Well 843-118-2 is 5.9 miles southwest of Sanford and about one-fourth
mile south of Five Point.?, or the junction of U. S. Highways 17 and 92
and State Highway 419. The hydrograph for this well shows a general
decline in water level of 2 or 3 feet between 1935 and 1956. The 1935
water levels in both 844-117-2 and 843-118-2 are less than 1 foot below the
water levels measured in the fall and winter of 1953, the highest water
levels of record.
The hydrograph of well 842-117-2, at Wagner (south of Lake Jessup),
shows the 1933 and 1935 water levels to be approximately the same as








REPORT OF INVESTIGATIONS No. 27


3- ---


331 MILES 01-P OF OVrEO

TOTAL TOTAL TOTAL TUI.L OTAL| TOTAL TOAL
S4MB 5e 4L" T 9W S a7 t 4T7AR 4S 5M0 4ft"

14









Figure 14. Hydrographs of wells 841-113-1, 842-117-2, 843-118-2, 844-117-2,
846-116-11, and the monthly rainfall at Sanford.








FLORIDA GEOLOGICAL SURVEY


30 ---

28

26


24 --r-
22

2
38

3-

34
-J
L.32
,L, /
LJ
_J 3C---

< 2--
LLI3
z )
Z34-

W032-
30:------
42


.4
w
Lii
U-



4--
<4 2------1







4- 4
4C


34-

6_
34-
34 ---


II__ __H WELL 849-118-5 ll'
3.0 MILES NORTHWEST OF SANFORD
I I I I







-- -WELL 848-119-4,-
L2 MILES SOUTH OF LAKE MONROE








__ _WELL 844-115-8,
5.2 MILES SOUTH OF SANFORD






WELL 840-112-1 1"
0.3 MILE NORTH OF OVIEDO











WELL 839-113-1,
1.2 MILES SOUTHWEST OF OVIEDO


Figure






REPORT OF INVESTIGATIONS No. 27


those of 1955 and 1956. The hydrograph of well 841-113-1, 1.6 miles
northwest of Oviedo, shows a water-level decline of 2 or 3 feet between
1937 and 1956. The water levels in 1937 are only about 1 foot lower than
the high water levels during 1953. The 2- or 3-foot decline might be
caused by the increased number of wells and the corresponding increased
use of ground water in the farming area north of Oviedo.
Hydrographs of six wells are shown in figure 15. Well 849-118-5, 3.0
miles northwest of Sanford, and well 848-119-4, 1.2 miles south of Lake
Monroe, both show water-level fluctuations of almost 8 feet. The hydro-
graphs do not show any significant trend of water level over the period
1933-56.
The water level in well 844-115-8, 5.2 miles south of Sanford, fluctu-
ated less than 6 feet during the period of record and declined about 4
feet between 1983 and 1956. This decline is probably due to increased
use of water in the vicinity. The hydrograph of well 844-115-8 shows that
the water level during 1937, a year with nearly normal rainfall, was
almost 2 feet higher than the highest water level measured in 1953, the
year of the highest rainfall ever recorded at Sanford.
Another well that shows. a general water-level decline of about 3 or 4
feet for the period of record is well 840-112-1, 0.3 mile north of Oviedo.
The hydrograph of this well and the hydrographs of wells .839-113-1
and 838-113-2 show evidence of increased use of water around Oviedo
since 1937. Well 839-113-1, 1.2 miles southwest of Oviedo, is in an area
of extensive ground-water use and has water-level fluctuations. as large
as 9 feet within short periods of time. These rapid changes in water level
tend to mask out any general trend in the water level. Well 838-113-2,
at Slavia, shows a water-level decline similar to that shown by well
840-112-1.
Hydrographs of 10 other wells that show past records of water levels
are included in the section of this report entitled "Salt-Water Contami-
nation."
An illustration of the relationship of the water level in an artesian
well to the water level in a nearby nonartesian well is shown on figure
16. These wells are about 1X% miles west of Paola, in an area of very
little ground-water use. Most of the water-level changes, therefore, are
due to variations in the amount of rainfall. The artesian well obtains
water from the Hawthorn Formation and the nonartesian well obtains
water from the Pleistocene sands..
The hydrographs for the two wells show similar fluctuations. The
elevation of the water level in the nonartesian well varies from 3.5 to 6
feet above the water level in the artesian well. Therefore, the shallow







FLORIDA GEOLOGICAL SURVEY


0i 50
iL.
< 48

4 46

u.L 44
o
42
I-
Ul
- 40

14t
> 3E


Figure 16. Hydrographs of wells 846-123-2 and 847-123-2, about 1% miles
west of Paola.

sand aquifer probably recharges the Hawthorn Formation in this area.
The shallow well had a maximum water-level fluctuation of 8 feet and the
deep well had a maximum water-level fluctuation of 6 feet during the
period of record shown in figure 16.

SURFACE WATER
SPRINGS
Seminole County has several large artesian springs and several small
nonartesian (water-table) springs. Most of the artesian springs are along
the Little Wekiva or Wekiva rivers. These include Sanlando Springs, Palm
Springs, and Sheppard Spring, all about 8 miles west of Longwood and
along the Little Wekiva River.
ARTESIAN SPRINGS
Sanlando Springs is in the NESE3 sec. 3, T. 21 S., R. 29 E., on
the east bank of the Little Wekiva River. The springhead forms an
irregularly shaped pool about 50 feet in diameter. Ferguson, et al.,
(1947, p. 149-153) gives descriptions and data about Sanlando, Palm,
and Sheppard springs. The temperature of the water from Sanlando
Springs was 74F, and the maximum depth of the water at the spring-
head was 13.2 feet on April 23, 1946. The average of three discharge
measurements of the spring is 18.4 mgd. Table 4 and figure 33 show an
analysis of the water from Sanlando Springs. The water is moderately
hard and similar to water found in most artesian wells in the southwest


V WELL 847-123-2
S-- Nonortesian well, -
V 8 feet deep




WELL 846-123-2
Artesian well,
70 feet deep

1953 1954 1955 1956


I






REPORT OF INVESTIGATIONS No. 27


section of Seminole County. It is classed as a calcium bicarbonate
water and the total hardness (as CaCO3) was 105 ppm.
Sheppard Spring is in the SWNW, sec. 2, T. 21 S., R. 29 E., 0.2
mile north of Sanlando Springs. The spring forms a pool about 70 to 80
feet in diameter. The temperature of the water was 74F. and the
yield was 11 mgd on July 25, 1944. Chemical analysis of the spring
water collected on the above date shows the water to be very similar
to the water from Sanlando Springs, having a mineral content only
slightly higher. The spring is used as a private swimming pool by the
owner.
Palm Springs is in the SWKNW, sec. 2, T. 21 S., R. 29 E., 0.3 mile
north of Sanlando Springs. The pool, formed by concrete retaining walls,
is rectangular. The flow of the spring was 6.3 mgd on November 12,
1941, and 6.7 mgd on August 25, 1954. The spring is used for swimming.
Miami Springs is in the NWhNWl sec. 32, T. 20 S., R. 29 E., 0.25
mile south of the Wekiva River. The spring forms an oblong pool which
is used as a private swimming pool. Florida Geological Survey Bulletin
No. 31 (Ferguson, et al., 1947, p. 179, table 4) gives data on Miami
Springs but incorrectly lists the spring in Orange County. The flow
of the spring was 3.7 mgd on August 8, 1945.
In the spring of 1957 land-clearing operations helped develop a
new artesian spring in Seminole County. The spring is 0.4 mile southeast
of Miami Springs and is called Sweet Water Spring. The spring, shown
in figure 17, is in the NW, sec. 32, T. 20 S., R. 29 E., 100 feet north of
the Wekiva Spring Road and about 25 feet west of Sweet Water Creek.
Figure 17a shows the springhead pool and the short run into Sweet
Water Creek, and figure 17b shows a closeup of the spring pool, which
is about 8 to 10 feet in diameter, and the turbulence of the boil. The
total flow of the main spring and several much smaller springs is estimated
to be about 100 gpm.
A similar spring developed in the NENE,4 sec. 36, T. 20 S., R. 30 E.,
about 100 feet south of Lake Jessup, in the spring of 1952. This
spring, which was developed by dredging a small boat basin on prop-
erty owned by William Crook, flowed about 2 mgd shortly after it
formed. An attempt was made to measure the flow on November 4,
1952, but no measureable flow could be detected.
The water level in well 842-116-4, 700 feet south of the spring, was
39.78 feet above sea level on May 14, 1952. The well was measured on
May 28, 1952, 3 days-after the spring began flowing, at which time the
water level was 35.62 feet above sea level. Most of the 4-foot decline of
water level was probably caused by pressure relief due to flow of the









FLORIDA GEOLOGICAL SURVEY


1- 'yr I S'~ t \\ak'r Spring a view of ~priIP' mci SlIrrOIifldlfl(' ir


s
or









REPORT OF INVESTIGATIONS No. 27


b, closeup view of spring.


r







FLORIDA GEOLOGICAL SURVEY


Figure 18. Heath Spring, 0.7 mile northwest of Geneva.







REPORT OF INVESTIGATIONS No. 27


spring. At well 842-116-1, 0.65 mile southwest of the spring, the water
level declined 3 feet from April 4, 1952, to May 28, 1952.

WATER-TABLE SPRINGS
Elder Spring is in the NEO NW, sec. 23, T. -20 S., R. 30 E., about
5 miles south of Sanford. The flow of the spring is rather small, and a
small pump and motor delivers the water to a building where it is
bottled for sale. The chemical analysis of Elder Spring water is shown
in figure 33 and table 3. The water is very soft, as the total hardness
(as CaCo3) is only 29 ppm and is classed as a calcium bicarbonate type.
Heath Spring is in the SW4 sec. 16, T. 20 S., R. 32 E., 0.7 mile north-
west of Geneva. The yield of the spring ranges from 5 to 10 gpm, and
the water is occasionally used for drinking purposes and in storage
batteries. Figure 18 shows a view of the main spring pool. A chemical
analysis of the water, which is classed as a sodium chloride type, is
shown in table 3 and figure 33. The water is very soft, the total hardness
(as CaCo3) being only 7 ppm. Figure 19 shows the temperature and the

z- _



I--^-- 1 ---
o 50






- 70

o 68----

66 1952 1953 1 954 | 1955 3 1956

Figure 19. Temperature and chloride content of Heath Spring.
chloride content of water from Heath Spring. The water temperature
ranges from 66 to 74F. and varies according to the seasonal temperature
changes. The chloride content ranges from 12 to 26 ppm and is probably
influenced by the amount of rainfall and the direction of winds, which
carry salt spray from the ocean.
LAKES
Water-level measurements of five lakes in Seminole County (fig. 20)
were made for comparison with rainfall records, norartesian water levels,
and artesian water levels.
Lake Geneva, half a mile east of Geneva, had the largest fluctuations







FLORIDA GEOLOGICAL SURVEY


.Ile PRAIRIE LAKE
87



85 -

0.A ______________________ _____________________ __________


-1
Lii
L11


Ld






Lii
0



Li1
LIi
LL-

z


LLI
LIL
-1

ILU


57 ________
57

5G


43" LAKE MARY

4*2 -,

41




38-
LAKE JENNIE



35---------------------w


34 !

29
LAKE GENEVA






23
27------ ^-----









22-

( 1 9 I I tI I I 1 1 1 1 1 1 1 I I I lll 1 1 1l I I I I 11I I 1I I I I I I I I I
1952 1953 1954 1955 1956
Figure 20. Hydrographs of five lakes in Seminole County.






REPORT OF INVESTIGATIONS No. 27


of any lake measured. Measurements begun in the fall of 1953 and
continued through 1956, indicate a fluctuation of almost 7 feet during
this period. The lake levels ranged from a high of 28.2 feet above sea
level to a low of 21.5 feet above sea level. During the period of record,
the lake level was from 2 to 6 feet higher than the water level in nearby
artesian wells, indicating that the water of Lake Geneva is obtained
mostly from the nonartesian aquifer and in part directly from rainfall
that falls on the lake. Figure 21, a photograph of Lake Geneva taken
on August 13, 1957, shows a small boat dock that was unusable owing
to the low water level at that time.
Lake Jennie, about 2 miles south of Sanford, had a fluctuation of less
than 2M feet during the period 1952-56 (fig. 20). The lake level usually
stands from 4 to 7, feet higher than the water level in well 847-116-1,
an artesian well half a mile north of the lake. The water level in the
lake stands from 7 to 10 feet higher than the water level in well
847-116-2, an artesian well 0.8 mile northeast of the lake, and from
0.8 foot below to 3.5 feet above the water level in well 846-116-11,
an artesian well 0.3 mile south of the lake. The artesian pressure head
in well 846-116-11 was. higher than the lake level for only a few months
during the fall of 1953. Most of the time, the lake level stands above
the piezometric surface.
Lake Mary, about 0.2 mile southeast of the town of Lake Mary,
fluctuated more than 4 feet during the period of record. At different
times, the lake level stood either above or below the water level in
well 845-119-1, an artesian well 0.25 miles northwest of Lake Mary.
During wet periods the lake level was as much as 3 feet lower than
the piezometric surface, and during dry periods, the lake level was as
much as 2 feet above the piezometric surface. During dry periods, there-
fore, the lake is a potential source of recharge to the artesian aquifer,
and during wet periods the artesian aquifer could contribute water to
Lake Mary.
Lake Orienta, half a mile west of Altamonte Springs, fluctuated less
than 4 feet during the period of record. Figure 22 shows a comparison
of the lake level with the water level in artesian well 840-120-2, 1.6 miles
east of the lake, and the water level in nonartesian well 839-122-1, 650
feet northwest of the lake. The lake level is generally about 2 to 4 feet
higher than the water level in the artesian well, except during very wet
periods when the water-level altitudes are about the same. However, in
an artesian well (839-121-5) 400 feet north of Lake Orienta, the water
level was below the lake level during both wet and dry periods. The
lake level was generally 2 to 4 feet above the water level in the non-
artesian well (839-122-1).






iI


Figure 21. Lake Geneva showing the low water level on August 13, 1957.


s::l:







REPORT OF INVESTIGATIONS No. 27

61

60-

59

58 LAKE ORIENTA,
Q5 MILE. WEST OF ALTAMONTE SPRINGS
57-

56
51 --- i ------------ --- ---
61

60

59 /LL
/
58

57 -- 7i i

56 /
Ariesian well
55 ______ ____________

54

53
WELL 840-120-2, 1.5 MILES FROM LAKE
ORIENTA AND 0.5 MILE SOUTHWEST OF FERN PARK
52
59

58

57 1

56

55 -
Nonartesian well
54

53
WELL 839-122-1, 700ft FROM LAKE ORIENTA AND
0.8 MILE WEST OF ALTAMONTE SPRINGS
52 1937 1951 1 1952 I 1953 | 1954 1955 1956
Figure 22. Hydrographs of wells 839-122-1, 840-120-2, and Lake Orienta.


I






FLORIDA GEOLOGICAL SURVEY


Prairie Lake, 0.3 mile southeast of Altamonte Springs, fluctuated
about 3 feet during the period of record. The lake level is about 30
feet higher than the piezometric surface in the vicinity.
WELL EXPLORATION
ELECTRIC LOGS
The electric log is a very useful aid in the identification of formations
penetrated by a well and of fluids these formations contain. However,
in limestone formations of the Floridan aquifer, electric logs preferably
should be interpreted in conjunction with other aids such as well cut-
tings or drilling time logs. The electric log is a graph of the electrical
properties of the rocks and fluids penetrated by the well. The electrical
resistivity and self-potential are recorded with the depth as the abscissa
of the graph.
Electrical resistivity is a measure of the resistance of material to
the flow of an electric current. The term "relative resistivity" is used in
this report because the electric logging equipment used was the single-
electrode type which does not yield precise results.
Water is the main fluid that fills the void spaces in the limestone
sediments and conducts electricity. Pure water has a very high resistivity
but ground water has a much lower resistivity because of its dissolved
mineral content. In general, in Seminole County, high relative resistivity
indicates dense sediments that yield little water.
In Volusia County, Wyrick and Leutz (1956, p. 23) found a cor-
relation between the dense layers of limestone, high relative-resistivity
readings, and increased drilling time. These dense layers of limestone
generally restrict the vertical movement of water. The application of the
resistivity curve of electric logs made of limestone aquifers in Seminole
County has been limited to the location of porous and dense sections in
the limestone and to the determination of other lithologic changes.
The self (spontaneous) potential measures the difference in voltage
between an electrode in the well and a ground at the surface. The
potential differs according to the nature of the beds traversed. The self
potential log is used to distinguish between permeable and impermeable
deposits. In some wells the self-potential curve shows a difference be-
tween fresh and salty water. As the open-hole part of the wells logged in
Seminole County was in limestone, the self-potential curves yielded
little information.
RESISTIVITY, FLOW, SALINITY, AND TEMPERATURE MEASUREMENTS
Figure 23 shows an electric log, a current-meter traverse, and salinity
measurements in well 845-117-10, about 3.6 miles south of Sanford. The







FLORIDA GEOLOGICAL SURVEY


0i 50
iL.
< 48

4 46

u.L 44
o
42
I-
Ul
- 40

14t
> 3E


Figure 16. Hydrographs of wells 846-123-2 and 847-123-2, about 1% miles
west of Paola.

sand aquifer probably recharges the Hawthorn Formation in this area.
The shallow well had a maximum water-level fluctuation of 8 feet and the
deep well had a maximum water-level fluctuation of 6 feet during the
period of record shown in figure 16.

SURFACE WATER
SPRINGS
Seminole County has several large artesian springs and several small
nonartesian (water-table) springs. Most of the artesian springs are along
the Little Wekiva or Wekiva rivers. These include Sanlando Springs, Palm
Springs, and Sheppard Spring, all about 8 miles west of Longwood and
along the Little Wekiva River.
ARTESIAN SPRINGS
Sanlando Springs is in the NESE3 sec. 3, T. 21 S., R. 29 E., on
the east bank of the Little Wekiva River. The springhead forms an
irregularly shaped pool about 50 feet in diameter. Ferguson, et al.,
(1947, p. 149-153) gives descriptions and data about Sanlando, Palm,
and Sheppard springs. The temperature of the water from Sanlando
Springs was 74F, and the maximum depth of the water at the spring-
head was 13.2 feet on April 23, 1946. The average of three discharge
measurements of the spring is 18.4 mgd. Table 4 and figure 33 show an
analysis of the water from Sanlando Springs. The water is moderately
hard and similar to water found in most artesian wells in the southwest


V WELL 847-123-2
S-- Nonortesian well, -
V 8 feet deep




WELL 846-123-2
Artesian well,
70 feet deep

1953 1954 1955 1956


I







REPORT OF INVESTIGATIONS No. 27 45


1 Z RELATIVE RESISTIVITY E ON
SELF POTENTIAL Ohm-melers rren meter) (ppm)
40 Ov 0 0 20 30 4 50 0

20-

0-

-20-

J -40 -

J -60 ? _

.i -80

-100-

o -120-





220
-140- 0





< -260-

-280
z_
- -220-

240





34 "Well 845-17-10
-280-

-300- >


-Obstruction.
-4 Well 845-117-10

Figure 23. Electric log, current-meter traverse, and chloride content of water from
well 845-117-10, 3.6 miles south of Sanford.






FLORIDA GEOLOGICAL StUVEY


most noticeable feature of the relative-resistivity graph is the highly
resistant zone at 290-300 feet below sea level, which represents a dense
layer of limestone. This dense layer probably is relatively impervious,
and restricts the vertical movement of water. The relative-resistivity
graph was useful to the city of Sanford, as it contributed to the decision
to deepen some city wells in the spring of 1956 when additional quanti-
ties of water were required. The Sanford well field is about half a mile
east of well 845-117-10. Before 1956, the wells were not deeperied be-
cause of the possibility of obtaining salty water. After exploring well
845-117-10, it appeared that the city wells could be deepened to about
280 feet below sea level without increasing the chloride content of the
water. The confining layer would prevent salty water, if present at a
lower depth, from moving upward and contaminating the water in the
producing zone. Four wells in the field were deepened as much as 100
feet without any increase in the chloride content of the water. Thb
bottom of the deepest city well is 180 feet below sea level.
The flow graph in figure 23 shows a slight flow in the well, although
the well was not flowing at the surface. The current-meter revolutions
were so slow that it was not possible to determine whether the flow was
upward or downward. The chloride content of water samples collected
at various depths in the well was relatively constant.
Similar information from well 840-107-2, about 2.1 miles north of
Chuluota, is given in figure 24. It shows a layer of very dense limestone
at about 340 to 365 feet below sea level. This dense limestone acts as
a confining layer for the salty water below. The chloride content of water
from the limestone below this dense layer is much higher than the
chloride content of water from the limestone above the layer, presumably
because the lower aquifer has not been flushed as completely as the
upper aquifer.
The velocity graph shows that most of the water was coming from
a very productive zone just below the dense layer. Even if the flow
of water is constant within the well, variations in the velocity graph
can be due to irregularities in the well diameter. Such irregularities
are probably responsible for the apparent differences in flow. The velocity
is more uniform in the cased part of the well, where the diameter of
the well bore is constant; however, the diameter of the rest of the
well bore differs because of caving of some of the relatively unconsolidated
rocks penetrated by the well. However, the velocity declines as the
water moves up the cased part of the well. This may be due to loss of
head by pipe friction and as a result of lifting the water to the surface
or small leaks in the casings. The chloride content of the water collected







iREPOIT OF INVESTIGATIONS No. 27 47





o. -- --- WM---- IV

l..,w .eu. "__.l /





-0 o-
0

-20

-40c


-60













-1000
Swell 840-107-2, 2.1 miles north of Chuluota,




-- -200

.220 -

S-240 --- ] -- -- -- ^ -- -H -
I-
260 '- -


-300. U

-320 lie

.340 IL


0 befrucelon
-3600

Well 840-M17-2

Figure 24. Electric log, current-meter traverse, and chloride content of water fioni
well 840-107-2, 2.1 miles north of Chuluota.



at the surface was lower than the chloride content of water samples
collected within the well. This may be due to a small error in the field
determination of the chloride content of the water sample collected at
the surface.
The graph of the relative resistivity in well 848-116-12 (fig. 25),
about half a mile southwest of Sanford, indicates a dense layer of lime-
stone at about 250 feet below sea level. 'This may be the same hard
layer that is 40. to 50 feet lower in well 845-117-10 (fig. 23). The well
was not flowing at. the time of exploration and the current meter did not







FLORIDA GEOLOGICAL SURVEY


SELF POTENTIAL
10 my


RELATIVE RESISTIVITY
Ohm-meters
09 p 15


CHLORIDE
CONTENT
(ports per million)
50 400 4!


20



0-

-20-


______________________ II


Well 848-116-12


Figure 25. Electric log and chloride content of water from well 848-116-12, 0.5 miles
southwest of Sanford.


i <


0 u I

i!





















oi


z
0



IL



0
a


z
0

hi4
M ~ -----"

0 4 --------------- 1 C ___ ---
CL ______________^ -- =

az --------------~ [ -------- --


-1

LU
-60
_:
-80










U-I
: -160


LU -180-


LU -200-


z -220"


1 -240-
1.-
-260-


-280-


-300-


-320-


-340-


-36C


L


I







REPORT OF INVESTIGATIONS No. 27


indicate any movement of water within the well. The chloride content
of the water collected within the well did not show any significant
change at various depths in the uncased part of the well. The electric
log contained some unusual graphs in the cased portion of the well. As
the well is old and unused, the graphs might represent corroded zones
or holes in the casing. Water leaking through these holes might explain
the higher chloride content in the cased portion of the well.

A combination graph of well 841-110-12, about 2.7 miles northeast


of Oviedo, is shown in


20
ww






o -40-




-12





I-00
0 -14
Li
c-120-


U.

z -160
w

I-


,


SELF POTENTIAL
IOmv


figure 26. The graph of


RELATIVE RESISTIVITY
S Ohm-meters
S 5 10 15 20


the relative resistivity


VELOCITY
rev/sec of current meter j
0.5 1.0 15


Well 841-110-12
Figure 26. Electric log, current-meter traverse, and chloride content of water from
well 841-110-12, 2.7 miles northeast of Oviedo.


indicates that the resistivity of the rocks increases generally with depth.
The velocity graph shows that most of the flow apparently comes from
the uppermost 20 feet of limestone below the bottom of the casing.
The lower part of the well contributes only a very small amount of water
and the bottom 40 feet of the well apparently contributes none. The
chloride content of the water collected at various depths within the well


CHLOR
CO7TEN


E
__ _____ ___
M
0
7=



4 1!
13t

It -



.-- ,-"" ------ n
Lii0- j -________ = -)





I / z^
0.0
2-
U 1Z ______ ) ___ __ ^ _________I ___ __






50 FLORIDA GEOLOGICAL SURVEY


showed no difference except in the sample from the bottom of the well,
which contained about 55 ppm less chloride than the four shallower
samples. This bottom sample was collected in the zone of no measurable
flow.
The graphs for well 838-113-3, about 2.5 miles southeast of Oviedo
(fig. 27), show that almost all the water is obtained from the uppermost


_j 20-
LJ
LJ 0-
--

S-20-


z -40-
4
U1
M -:60-
0
-80
0
LI
g!-loo-
LU
^-420


Li -140-
Li
LL
Z -160-

0 -180-
I-
4^


Iz
20
cc,


SELF POTENTIAL
I l Onw


RELATIVE RESISTIVITY
Ohm -meters
25 50 75 100


VELOCITY
rev/sec of current meter)
) 0.5 i.0 LF


hi
IU


0Z.
Ob t ru, !

-s .____.___. _________ __-0
_j



til _?.------- -.________ -______________ ____ _- _
w- 0'



-a tt ___________ ___ __ ___________________ f___^_

42 -) ______ _





iii -- "-r --
r- .__
04






0 -
.2

-g -_______________ bstrution ____ ____ ____

4O obstruction n


WELL 838-113-3
Figure 27. Electric log and current-meter traverse in well 838-113-3, 2.5 miles
southeast of Oviedo.

80 feet of limestone below the bottom of the casing. The graph of the
relative resistivity shows that many thin, dense layers are present in the
limestone. Most of the flow seems to be obtained from the areas of low
resistivity.
The combination graph of well 842-111-6, about 2.3 miles northeast
of Oviedo (fig. 28), shows that most of the water is obtained from


















S__________ '"" De ith wll Dfptiof wll
Kat -ot iatlre n X


I0
--o fro I I Iment de m en a
comi ltUd will.





















WELL 842- 111-6

Figure 28. Electric log, current-meter traverse, chloride content, temperature, and
yield of water from well 842-111-6, 2.8 miles northeast of Oviedo.

Ux
I^





FLORIDA GEOLOGICAL SURVEY


the Hawthorn Formation. The rest of the water is obtained from the lime-
stones of the Ocala Group. Below the bottom of the casing, the points of
higher velocity correspond with the layers of higher relative resistivity.
These more resistant layers are hard and they are affected very little by
caving; the well diameter, therefore, is generally smaller at these layers.
The smaller diameter of the well bore restricts the flow and increases
the velocity of the water.
A study of the current-meter traverse in the cased part of the well
indicates that the casing may be leaking somewhere in the zone from 30 -
to 45 feet below sea level. The current-meter revolutions decreased from
3.2 per second at 45 feet below sea level to 2.0 revolutions per second
at 30 feet below sea level. The velocity measurements within the casing
were more uniform in the other wells that were explored.
Measurements of the chloride content of the water were taken at
various depths within well 842-111-6 by two different methods. One set
of water samples was collected from the bottom of the well with a bailer
while the well was being drilled. The chloride content of these bottom-
water samples increased from 450 ppm in a sample collected at 55 feet
below sea level to 755 ppm in a sample collected at 190 feet below sea
level. These samples were collected during the period January 12-27,
1963. On December 3, 1956, water samples were collected at various
depths within the well. The chloride content of these samples ranged
from 900 to 960 ppm. The composite sample of the chloride content of
water collected at the surface was about 200 ppm above the highest
chloride content measured while the well was being drilled in 1953.
The discharge temperature of the water, while the well was being
drilled, increased from 74.5 to 76.50F. from the bottom of the casing
to the bottom of the well. This amounts to an increase of about 1F. in
the temperature of the water discharged for every 60 feet increase in
well depth. However, these temperature measurements were made of
the water discharged at the surface and .do not represent the actual
temperature of the water at depth in the well.
The graph of the increase in yield shows that the first flow of water
was 50 gpm when the bottom of the well was 53 feet below sea level.
The yield increased to almost 400 gpm during the next 12 feet of drilling.
The well yield at the surface was 670 gpm when the well was completed.
Almost 4 years later, the well yield was 700 gpm.
The graph of the relative resistivity of the rocks at well 847-113-31
(fig. 29), about 3.0 miles southeast of Sanford, indicates many thin resis-
tant (dense) layers in the Avon Park Limestone. The graph of .the
chloride content of water samples collected within the well shows an






REPORT OF INVESTIGATIONS No. 27


WELL. 847-113-31

Figure 29. Electric log and chloride content of water from well 847-113-31, 3.0
miles southeast of Sanford.


-IJ
LJ
>
LU
_2

LU
(I)
* Z




0
I--

W
W-
Cr
Ld
W
LL-
LU


LJ
LJ
b_
LU-
Z

C
Li
0
D
III
Q
-J






FLORIDA GEOLOGICAL SURVEY


Prairie Lake, 0.3 mile southeast of Altamonte Springs, fluctuated
about 3 feet during the period of record. The lake level is about 30
feet higher than the piezometric surface in the vicinity.
WELL EXPLORATION
ELECTRIC LOGS
The electric log is a very useful aid in the identification of formations
penetrated by a well and of fluids these formations contain. However,
in limestone formations of the Floridan aquifer, electric logs preferably
should be interpreted in conjunction with other aids such as well cut-
tings or drilling time logs. The electric log is a graph of the electrical
properties of the rocks and fluids penetrated by the well. The electrical
resistivity and self-potential are recorded with the depth as the abscissa
of the graph.
Electrical resistivity is a measure of the resistance of material to
the flow of an electric current. The term "relative resistivity" is used in
this report because the electric logging equipment used was the single-
electrode type which does not yield precise results.
Water is the main fluid that fills the void spaces in the limestone
sediments and conducts electricity. Pure water has a very high resistivity
but ground water has a much lower resistivity because of its dissolved
mineral content. In general, in Seminole County, high relative resistivity
indicates dense sediments that yield little water.
In Volusia County, Wyrick and Leutz (1956, p. 23) found a cor-
relation between the dense layers of limestone, high relative-resistivity
readings, and increased drilling time. These dense layers of limestone
generally restrict the vertical movement of water. The application of the
resistivity curve of electric logs made of limestone aquifers in Seminole
County has been limited to the location of porous and dense sections in
the limestone and to the determination of other lithologic changes.
The self (spontaneous) potential measures the difference in voltage
between an electrode in the well and a ground at the surface. The
potential differs according to the nature of the beds traversed. The self
potential log is used to distinguish between permeable and impermeable
deposits. In some wells the self-potential curve shows a difference be-
tween fresh and salty water. As the open-hole part of the wells logged in
Seminole County was in limestone, the self-potential curves yielded
little information.
RESISTIVITY, FLOW, SALINITY, AND TEMPERATURE MEASUREMENTS
Figure 23 shows an electric log, a current-meter traverse, and salinity
measurements in well 845-117-10, about 3.6 miles south of Sanford. The





FLORIDA GEOLOGICAL SURVEY


increase of chloride content from 650 to 675 ppm as the depth increased
about 90 feet. The well was not flowing at the surface when the water
samples were collected. An attempt was made to determine if the well
had any internal movement of water but an obstruction prevented the
current meter from being lowered more than 23 feet below the surface.
Figure 30 shows the amount of casing, the depth, and current-meter
traverses for two wells near Oviedo. Well 842-112-2, about 2.3 miles


WELL 842-112-2 WELL 842-111-7
Figure 30. Current-meter traverse and chloride content of water from wells 842-112-2,
2.3 miles northeast of Oviedo, and 842-111-7, 2.3 miles northeast of Oviedo.

northeast of Oviedo, has about 65 feet of open hole in the Floridan
aquifer below the bottom of the casing. The bottom measurement of
the current meter in this well indicated a substantial flow which
increased upward to the bottom of the casing.
The graph of the velocity in well 842-111-7, about 2.3 miles northeast
of Oviedo, shows a small flow in the bottom 25 feet of the well. Most
of the flow, however, is obtained from the zone between 100 and 180 feet
below sea level. The chloride content of the water discharging at the
surface was 1,300 ppm. The chloride content of water samples collected
within the well ranged from 1,270 to 1,345 ppm. The sample at the





REPORT OF INVESTIGATIONS No. 27


surface represents a composite of the chloride content of water
obtained from all the producing zones within the well.

QUALITY OF WATER.
The wide range in the chemical composition of ground water in Semi-
nole County is shown by analyses of samples of the water. Some of the
ground water is excellent for ordinary use and some cannot be made
suitable for general use by any practical treatment.
The amount of dissolved mineral matter in water from the Floridan
aquifer ranges from low in the recharge areas of the hilly uplands to high
in the discharge areas of the lowlands. Stubbs (1937, p. 27) concluded
that the highly mineralized water in Seminole County was coming from
the Coskinolina Zone (Avon Park Limestone). Information collected
during this investigation has shown that the area in which the well is lo-
cated is more important in regard to the dissolved solids content of water
than the geologic formation that the well penetrates.
Samples of ground water for chemical analyses were collected in every
section of the county, but the most intensive sampling was done in
the areas. in which the water is highly mineralized. These areas gener-
ally include most of the areas of artesian flow. The chemical analyses were
made by the Quality of Water Branch of the U. S. Geological Survey.
The dissolved chemical constituents of water are reported in parts per
million (ppm). A part per million is a unit weight of a constitutent in a
million unit weights of water. Thus, a water sample containing 1 ppm of
iron (Fe) contains 1 pound of iron in a million pounds of the water sam-
pled. In order to show water analyses graphically, the cations and anions
may be expressed in chemically equivalent weights or equivalents per mil-
lion (epm); parts per million may be converted to equivalents per million
by dividing the parts per million by the combining weight of the respec-
tive cation or anion. Specific conductance is reported in reciprocal ohms
mhoss); pH is reported in standard pH units; and color is reported in
dimensionless units defined by the standard platinum cobalt scale.
The mineral constituents of natural waters generally reflect the com-
position and solubility of the rock materials with which the waters have
been in contact. In Seminole County, the minerals found in ground water
are not obtained entirely from rocks and soils. Some of the mineralization
of ground water in Seminole County probably comes either from sea
water that entered the rocks during the interglacial periods of the
Pleistocene Epoch, or from sea water that was trapped in the rocks when
they were deposited.





FLORDA GEOLOGICAL SURVEY


COLOR
Color in water may be of natural mineral, animal, or vegetable origin.
It may be caused by metallic substances, humus material, peat, algae,
weeds or protozoa. Industrial wastes may also cause color; color may
range from zero to several hundred units. Although color is not harmful
to people, it is objectionable when present in noticeable amounts. Color
begins to become undesirable in quantities above 20. All except 2 of
the 22 samples on which color determinations were made had a color of
less than 10. Color determinations of 22 ground-water samples in Seminole
County ranged from 1 to 25 (table 4).

SPECIFIC CONDUCTANCE
The specific conductance is a measure of the ability of the water to
conduct an electric current. The more dissolved mineral matter in the
water, the better it will conduct an electric current. Thus, specific con-
ductance indicates in a general way the relative mineralization of the
water. The specific conductance of 179 ground-water samples in Seminole
County was found to range from 135 to 21,900 micromhos at 250C.
(table 4).
SILICA
Most silica (SiO2) in water is probably derived from silicate minerals
other than quartz. Silica is of little significance in the range normally
found except when the water is used for boiler feed water. A recom-
mended upper limit of silica for boilers operating at 400 pounds per
square inch or above is 1.0 ppm (Rainwater and Thatcher, 1960, p. 259).
Silica in 20 ground-water samples in Seminole County was found to range
from 7 to 21 ppm.
IRON
Iron (Fe) is dissolved from almost all rocks and soils by rainwater
and ground water during the process of weathering. In addition, some of
the iron detected in ground water may have been dissolved from the well
casing and pipes. A concentration of more than about 0.3 ppm of iron in
water is objectionable, as it stains porcelain, plumbing fixtures, and
clothing. It imparts an undesirable taste, and oxidation of the iron forms
a reddish brown sediment. Excess iron can usually be removed by aeration
and filtration but some waters require more elaborate treatment.
The concentration of iron in the ground waters of Seminole County
differs considerably from place to place. The highest iron concentrations
are in artesian water from wells drilled in the lake regions. The presence
of a considerable amount of iron is usually associated with the presence
of a nearby recharge area. The total iron content in 38 ground-water
samples in this area ranged from 0.00 to 5.9 ppm. Many of the shallow






TABLm 4. Chemical Analyses of Water from Wells in Seminole County
(Analyses in parts per million, except specific conductance, color, and pH, by U.S. Geological Survey)

Hardness
Dis- as CaC03 Specific
solved con- Hy-
Date of Cal- Mag- Potas- Bicar- Sul- Chlor- Flu- Ni- solids duct- drogen
Well No. collection Silica Iron cium nesium Sodium sium bonate fate ide oride trate (residue Cal- ance Color pH sulfide
(iO02) (Fe) (Ca) (Mg) (Na) (K) (HC03) (804) (Cl) (F) (NOa) at cium Non- (mi- (HaS)
180C.) mag- car- cromhos
nesium bonate et250C.)


1 1 2


836-102-1
836-107-1
836-113-1
836-117-1
887-101-1
837-102-1
837-102-8
837-102-3
837-103-1
837-103-2
837-109-1
837-114-1
887-115-1
837-119-2
888-103-1
838-106-1
838-106-2
838-107-1
838-113-3
838-113-3
838-115-2
838-116-2
838-120-1
888-121-4
838-123-1,
838-125-1
8838-126-1
839-102-1
839-104-1
839-109-1


2- 3-55
3- 1-54
2- 7-55
3- 1-54
11- 4-53
3- 1-54
2- 3-55
6-23-56
6-23-56
6-23-56
2- 7-55
8- 1-54
3- 1-54
2- 5-55
3- 1-54
3- 1-54
2- 7-55
11- 5-53
11- 5-53
6-23-56
2- 5-55
2- 5-55
6-25-56
2-26-54
2- 3-55
2-24-54
2-24-54
2- 2-54
2- 2-55
3- 1-54


3



......

15














......


4

...'..,


0.21



.46
.14







.....45
.12
..,.',















,...,.


5

148
58
43
29
164
97
100



50
34
26
43
134
53
39
46
36

36
56
44
45
30
22
148
84
49


6 7 8 9


66
1.7
9
11
71
29
43



8
7.3
1
7.4
75
5.1
1.8
2.6
8.8

8.3
3.4
5.1
12
16
11
86
33
16


..ii...
13
1,. ,,


,......
....9
.6
.9
,,..


264


153
142
,....,


10

318
1.0
2.0
8.0
348
132
180



6.5
1.0
1.0
2.0
306
4.0
2.0
1.5
8.0

10
2.0
,...,,,
1,0
2.0
2.0
4.0
338
112
25


11

815
8
8
7
930
308
460
.... .
12
80

12
8
6
7
1,010
7
9
18
24

8
8
7
5
6
8
9
1,140
435
185


12 13


0.1




.0



.0




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0.4



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1.1
0....,
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14 15

2,100 650
180 152
170 144
140 116
2,360 701
900 362
1,200 425



190 158
150 115
88 69
170 138
2,400 642
180 153
130 104
164 125
176 126

160 124
190 154.
160 131
200 164
160 140
140 106
1,700 725
1,100 345
530 190


16



,.....
......
547













10
......
.,....
......
,,...,
......
......
,....,
,.....



10o
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17

3,320
303
292
242
3,720
1,520
2,070
494
570
325
251
151
288
3,880
304
231
2906
311

268
324
447
269
351
275
236
4,420
1,860
800


. ....
.,....

......
,o,....
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..,...


. ,. ...,
6
o
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18 19 20


8.0
7.8
7.9
7.6
7.6
7.3
7.7



7.9
7.8
7.8
8.0
7.4
7.8
8.2
7.6
7.6

7.7
8,1
8.1
8.5
7,7
7.9
7.6
7.7
7.9


12
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514












TAWUE 4. (Continued)


7 8 U


13 11


839-113-1
830-116-1
839-120-1
830-120-4
839-125-1

830-125-2
840-103-2
840-107-3
840-108-1
840-110-8

840-112-2
840-115-1
840-117-4
840-118-1
840-119-1

840-120-3
840-124-1
840-125-3
841-106-1
841-109-2

841-110-1
841-110-2
841-110-5
841-110-5
841-110-0

841-110-9
841-110-12
841-110-12
841-111-1
841-112-2

841-113-1
841-114-1
841-118-2
841-120-2
841-120-5

841-122-1
841-125-1
842-106-1
842-106-2
842-107-1


3- 1-54
2-2-654
2-2a-54
11-25-511
(1-25-5(1

4-10-52
3- 1-54
3- 1-54
2- 3-55
2- 5-55

3- 1-54
2- 5-55
6-25-50
2-26-54
2-26-54

11- 5-53
2-24-54
2- 3-55
11- 4-53
2- 5-55

3- 1-54
3- 1-54
2- 5-55
0-23-50
11- 5-53

0-23-50
11- 5-53
0-23-56
2- 5-55
3- 1-54

2- 5-55
2- 5-55
2- 5-55
6-25-50
7- 6-56

2-24-54
2- 3-55
3- 1-54
3- 2-54
3- 1-54


. ., .i. ..
...... 1.7

II .08






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11 .31


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53
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26
143
04
48
58

44
38
29
32

40
31
14
08
104

82
01
90
94
102

04

43
53

43
44
29

28.7

27
33
42
43
78


II
5.5
20


7.8
88
21
14
20

0.1
8.0


10

0.3
9.1
0.0
8.6
91

00
11
72
83
40

08

20
19

15
14
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2.9
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400.

572


334
70

121










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10

28
1.0
1.0


5.0
304
43
20
70

4.0
3.0

5.0
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1.8
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2.0
0.5
220

145
10
170
172
113


172
34
44

33
43
2.0


1.0
2.5
1.0
1.0
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II


142
7
01.5
10
8

7
1,-I)10
243
82
320

20
8.5
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4.5
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5.5
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1,440

038
128
1,100
1,000
705


i,070
1409
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121
92
6.5
11
11

7.5
8.5
10
10
11


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...2
......
,.....,

,,,....
,,,...,


,.....,

.2
,,,..2
,......
.1
....,.,

....,..

..... ,

.1
....
.12I

.....2
......
.,....

..,...
.2
.2

......

......
..,...
......


,,,..


0.2










.5
'",.,
,,,...,


,....,o
,,,o,,
,.....

.5
".... o
..,...



.9
.. 0..

..,...
.,....
....
,9

...,..
3,0
......

,.....
...,...


,.,....
......


......
,...o.
,......


,......
133
127
,......
,o,....


420
150
220


118
3,000
700
340
800

200
100

150

158
140
80
2009
3,100

2,150
430
2,500
2,500
1,720


2,200
440
560

380
340
150
108

150
160
150
150
240


170
120
207


07
722
24(1
1701
250

135
128


123

138
115
02
205
034

452
190
520
570
444

514
2156
210

170
168
108
104'

129
136
117
120
200


,.,..,.
,..,....

...,..
,.....

,,.....
.,.....
.....,.


......
......

......

......
""i6'l

......

,......


......
. .. .

......

......!
"388






..,....
,......


714
'60
385
515
141

204
.1,010
1,130
570
1,320

340
274


254

270
244
135
457
4,940

3,370
723
3,940
3,940
2,790



742
944

649
578
250
234


251
279
251
256
403


...,.,.


3










7
...o..
..,.,..


...... o
,......


......
7
,,....
4
10..,
...,...
...,...



......

,.....


,...,..

,.....

"'i6"
......

,......
,....o.


__ I


I


7.t1
7.41



7,7
7.4
7.5
7.8
7.8

7.0
7.9
8.2
7.0

7.3
8.0
8.1
7.5
7.0

7.4
7.5
7.7
8.2
7.7


7.6

7.8
7.4

7.8
7.9
8.1


7.8
8.0
7.7
7.8
7.3


. o ,


, ,
..,
. ,
.o..
,,,.
....


o....





.. ,

12
1.
,...,
.. ..
.. ..
... .
. .
1.7
....
,.....

.,o


......
......








TABLE 4. (Continued)

1 2 3 4 6 6 7 8 9 10 11 12 13 14 15 10 17 18 19 20


842-110-2
842-110-3
842-111-4
842-111-8
842-112-1

842-112-1
842-115-3
842-116-1
* 842-116-1.
842-117-1

842-117-3
842-121-1
842-123-1
843-103-1
843-103-4
843-103-4
848-104-1
843-104-41
843-104-8
843-104-12

843-106-2
843-106-3
843-106-4
848-106-2
,843-106-7

843-110-1





1,844-104-4
844-111-7
844-116-2
848-118-2
844-1207-1

843-123-1
844-104-3
844-104-4
844-105-1
844-106-1

844-108-2
844-107-1
844-114-4
844-115-8
844-116-1


2- 5-55
3- 1-54
2- 5-55
2- 5-55
3- 1-54

6-23-56
2- 5-55
2-26-54
6-23-56
2-26-54
6-23-56
2-24-54
2-24-54
3- 2-54
2- 2-55

6-25-56
8- 2-54
3- 2-54
2- 2-55
2- 2-55

2- 7-55
3- 2-54
3- 2-54
6-25-56
6-25-56

3- 1-54
2-5-55,
2-23-54,
2-23-54
2-24-54

2-24-54
2- 2-55
2- 2-55
3- 2-54
2- 2-55
3- 2-54
4- 9-52
2- 2-55
2-23-54
2- 8-55


0.18








2.2












.10


94
69
79
96
51


38
. s...


34
60
277
271

71
1358
284
138

48
56
36


106
92
53
33
34
833
128
69
69
88
40
38
98
69
58


75
46
57
73
21

ii"'

9.0

8.8

9.0
17
330
342

7.0'
107
360
120

2.4
1.9
.5


97
74
39
8.1
7.1

8.9
92
5.4
2.4,
45

.5
2.5
47
45
44


......
......
......
......
......

......
......
. . .
......
......

......
......
......
......
......

......
. . .
. . .
......
......

......
......
......
......
......

......
21
......
......
......


0.03


1629





178


182
111
135
172
43

14 '
2.0

1.0

.i....
14,
112
840
1,000

1.....0
240
980
288

1.5
1.0
1.0


237
185
90
1.0
1.0

12
200
3
:3
108

4
3.0
138
117
100


1,160
680
840
1,100
252

18
9
12
8.5

10
9.0
100
5,440
5,450

5,400
60
1,750
5,600
1,910

10
10
10


1,570
1,070
544
18
7

6.5
1,440
38
20
6905

8.5
9
820
693
685


0.1

.0


...o.o


.0





















.0


......
......
.
......
......

......
......
......
.....
.

......
.
.
......
,.....

......
..

.....
......

......
0.1
......
..
......


2,600
1,620
1,880
2,450
600


170
""166'


'150
420
10,500
10,500

"'330'
3,530
10,900
4,100

170
180
120


3,400
2,500
1,280
170
140

140
3,170
300
230
1,620

135
150
1,880
1,680
1,410


54(
36(
43C
54(
21


132

...iii

122
220
2,050
2,080

206
776
2,190
840

130
148
92


664
535
294
116
114

119
685
194
182
.405
102
105
440
386
325


5 ... ... .
o :::; ::;
0 .. .... .

2 .:... .

' ......

!. ... .




! '. : : '
>. ... .


...... i


o......
'.:...':


4,090
2,550
2,960
3,870
1,070

308
290
276
274

274
258
717
16,500
16,600

16,200
561
56,780
17,200
6,520

287
308
205


5,370
3,920
2,010
286
235

239
5,000
804
406
2,540

228
234
2,950
2,480
2,220


7.7 ..
* 7.6 ......
. 8.0 ..
* 7.7 ..
* 7.5 ......

. ...... 15
7.8 ......
S 7.6 ......

.'7' 7 :7 : .

7.7 ....
7.7.
7.4 ..
7.6 ......

...... 14
7.7 ..
7.5 ......
7.8 .....
7.8 ..

7.9 ..
7.7 ......
7.9 ..

7......
...... ......
7.5 ......
7.8 ......
7.7 ......
7.4 ......
7.7 ......

7.4 ......
7.7 ......
7.9 ......
7.1 ......
7.7 ......
8.1 ..
7.7 ......
7.4 ....
7.8 ......


3.6
'".....
.,..,,,


.......
......
......
......
......

......
......
. . .
......
......

......
......
......
......
......

......
. . .
. . .
......
......

......
.. .
.. .
......
......

......
2
......
......
......












TABLE 4. (Continued)


844-116-1
844-117-8
844-117-8
844-120-1
8465-107-1

845-107-3
845-108-3
816-108-3
845-110-1
845-113-1

845-I 13-1
846-113-11
8(6-114-5
845-114-6
845-115-2

845-115-7
8456-117-7
845-117-10
8456-118-3
845-118-3

845-119-1
845-121-2
845-122-1
846-108-1
846-112-5

846-112-6
846-113-3
846-115-0
846-116-5
846-116-11

84&-116-11
846-118-3
846-118-4
846-119-3
846-119-4

846-121-2
846-122-1
846-123-1
847-103-3
847-107-1


2

6-25-568
3- 1-54
8-256-56
2-24.-64
3- 2-54

2- 7-a5
2- 7-55
f-25-58
3- 2-54
2- 2-55

6-2-586
1-30-53
1-30-53
1-31-53
2-25-564

2-25-54
3-18-42
8-28-51
2-25-54
6-26-56
11- 5-53
2- 4-55
2-25-564
3-2-54
2-23-54

2- 2-55
2- 7-55
2-25-54
2-25-54
8-28-51

2- 6-55
6-25-56
2-25-54
2-25-54
6-25-56

6-25-56
2-25-54
2-25-54
3-2-54
2- 2-55


3



....,.









"6:6
11
8.7



..0



14






7.0.
......
....

....

......


7




,.,...
.,,,..,


.4 f

0,37 62
..... 45
.40 .......
...... 4f
..... 37
84

4.0 .
.. 139
.... 114
.. .. 120
.05 108
.04 70
.07 58
...... 855
67
.11 43
.01 50
...... 69
2.8 .......

5.9 88
28
...... 28
46
99
. .. 107

...... 100
9. 9
.. 110
...... 66
0 66

...... 60
1.2 ... ...
...... 61
...... 37


...... 16

...... 37
...... 123


6

48
I 4.6
6.1
1,8

8.7

65.

75

81
71
25
.7
8.8

8.2
8.5
0.0
1.7

7.4
2.9
26
25
54

44
48
12
32
25

30


1.6

..ii...

6.6
1.0
58


905
1.0

1.0
2.0

8.0
2.5

205
188

192
188
64
1.5
2.0

6.0
0.5
8.0
1.0

22
2.0
41.0
60
142
130
118
24
90
68

78
4.0'
1.0


1.0
1.0
4.0
132


14 15 18i~ 17


_eJ-_l-


11


13
13
7
15

25
12

1120=

1,250
1,170
408
16
65

118
58
70
9.5

7
6.5
11
405
960

820
725
131
430
345

330
10 "

7.5
12

8.5
7.0
13
810


12



0.1
.o...,




.. 1




.1
.o....

,....





.1i
.1











.1
...2.
..... 2
....,,,
..,...,

......

.. .... .
,......
......I
......
......
..o...,
......
,......
......
,.....

."1

.2
,,....
......
,......,


13














.7
.2


1,300
170
......
170
148
240
240

2,820

2.850
2,410
950
200
270

430
246
294
222
. .....

204
110
260
1,010
2,110

1,880
1,780
560
950
868

800

120
.......o

140
90
140
2,040


344
131

140
100

196
228
old

594

632
562
278
148
173

218
138
162
180

175
82
221
352
490

430
445
324
298
268

275

99


119
67
99
545


142
154
182
......


,.,,,,

,.,...
,. ,
,.....

o.....
"....3


....,.
......

.,,,...
.....,

......
.. ....
18
......,
....o..

..o...
.o....
...,...
......

.,.....
......
.....o
138


632
227
11


37
41


6.4







....93...


219


...,...


132
...... ......
...... ..1... 46
...... 132....


2.100
284
292
285
250

407
416

4,486'
4,440
4,500
4.060
1,620
331
465

721

3668


351
188
435
1,790
3,330

2,950
2,800
943
1,660

1,360

206
263

224
242
150
236
3,200


14
5.6
.6


2.0


.,....,


18 19.

...... 7.4
...... 7.8

...... 7.7
..... 7.0

...... 7.7
...... 8.0

...... 7.4
7.7

7.4
3 7.4
4 7.6
5 7.4
...... 7.5

...... 7.8
10 7.5
25 7.6
...... 7.5
...... ......

9 7.3
..... 8.1
...... 7.4
...... 7.2
.... .. 7.4

...... 7.7
...... 7.7
...... 7.3
...... 7.8
15 7.7

...... 7.7

7.4

7.7


...... 8.6
...... 6.4
...... 7.5


12



..,...






12






......


,.....
,... .


......







TABLE 4. (Continued)

1 3 4 5 6 7 10 1 12 13 14 1 16 7 18 1 20


847-107-1
847-108-1
847-108-1
847-110-I
847-110-1

847-112-7
847-113-5
847-113-5
847-118-21
, 847-114-8
847-114-3
847-114-6
847-11-5
847-116-2
847-116-6
847-116-111
847-117-2
847-118-7
847-119-2
847-120-38
847-121-2
847-123-1
848-112-2
848-112-2
848-113-5
848-11-58
848-114-4
848-115-3
848-116-3
848-117-8
848-117-8
848-118-2
848-119-2
844-120-2
848-122-1
849-4105-1
849-117-1
849-117-1
849-118-8


6-25-586
2- 2-55
6-25-56
4- 9-52
3-2-54
2-23-54
2-23-54
6-25-56
2-23-54
2-28-54

6-25-86
8- 2-54
2-25-54
2-23-54
2- 7-55
2-23-54
2-4-855
4-9-52
2-25-54
2-25-54
6-25-56
2- 4-55
2-25-54
2-23-54
6-25-56
2- ,7-855
6-25-56
2- 7-55
6-14-51
2- 4-55
2-23-84
6-25-56
2-23-84
2-23-54
2-23-54
2-23-54
2-7-56
2- 4-5
6-25-86
2- 4-55


...... ......

.. .2 .....
...... ......
...... ......
...... ......
...... ......
...... ......
...... ......
...... ......
...... ......
...... ......

11 .11

. ... .
...... ......
...... ......
...... ......
...... .

::::::::::::.




...... ... ...

...... ......


122
326
144
157
107
24
58
84
79
80
77
83
a8
89
65
45
46
42
33

24
22
86

82
113
104
112
101
47
39
a1
27
313
129
"43"


63
441
"80"
70
50
29
37
33
17
22
8.3
16
5.1
12
15
10
6.9
3.4
3.9

7.3
9.2
26

36
32
41
50
48
9.0
6.6
2.2
10
310
64
.9.0


9.2


.6


148
... .


167


145


,i6."


112
1,180
218
220
135,
20
80
90
56
45
90
30
24
29
64
11
4.0
2.0
1.0

1.5
6.0
73

92
98
112
170
171
18
1.0
10
5,0
680
198
1.8Ts


5.0


1,920
13,900

2,660
2,880

1,880
1,230
1,360.
1,220
714


755 .....
7,450 .....
7,700 0.0
1,390 .0
1,420 ....
880 ....
579 ......
579
570
540
836 ......
260
518 ......
163 ......
94 ...
148 ......
249 .....
47 ......
10 .0


10 .1
5.5 ......
435 ......
10 .1
590 ......
582'" ....
700 .1
820 ......
756 ......

10 .....
8
0.5 ......
5,100
1,080 ......
"806 ::


564
2,630
688
678
472
176
296
344
268
290
326
272
166
274
224
154
143
119
99

90
93
320


...... 3,040
......21,900
......20,500
...... 4,950
...... 4,930
...... 3,100
1,940
....... 2,140
...... 2,120
.... 1,250
...... 1,240
2,030
..... 946
..... 600
.... 935
...... 1,130
..... 430
...... 324
.... 259
...... 215
... ... 281
...... 185
...... 197
...... 1,680
.. .. ,.....


720
...... 1,150
...... 6560
550
..... 638
...... 250
.1 188
...... 180
...... 130

...... 110
.... 120
...... 1,050
..... 248
...... 1,330
. ...... . 'i.1,410
.... 635
...... 1,900
...... 1,640
272
...... 145
167
.. .... 123
.... 10,000
...... 2,480
[''''["240'


2,100
'2;,220
2,990
2,690
495,
263
295
232
15,700
3,930
"' 'i6'


...... 7.3
...... 7.6
2 7.3
...... 7.4
.... .. 7.5
8.4
...... 7.3
...... 7.7
7.4
..... 7.5
7.7
..... 7.5
7.6
...... 7.6
7.9
8.3
8.1

.... 7.9
...... 8.0
..... 7.6

..... 7.7

5 7.7
.. 7.7



...... 7.6

7.56
...... 7.8
..... 7.5
... 7.7
''''. 8.1"


......












...*..





..9
.3


355 ......
418
430 300
485 ......
452 ......
184 .
125 .....
136 ......
109 .
2,060 ......
5885 .
"144.,


I











TABLE 4.


iDOC( ntled)


1 2 3 4 5 6 7 8 U 10 1t 1 13 14 16 l1 17 18 10 20

840-110-3 2-23-54 ... .... 4 12 ....... ...... ...... 21 88 ...... ...... 320 103 ...... 534 ...... 7.7 .....
849-111-8 2- 4-55 ..,., .. ... 4. 11 ... .. .. ..... .. .1,5 74 ...... ...... 280 1 0 .... 478 ...... 8 0 ......
849-1M0-2 2- 4-65 ..... ...... 57 17 ....... ...... ...... 48 170 ...... ...... 00 212 840 ...... 8.0 ......
840-121-2 2-23-54 ...... ...... 44 8.3 ....... ...... ...... 3.0 48 . .. 220 144 ...... 3 ...... 7.8 ..
840-123-1 -2 -54 ...... ....... 44 14 ....... ...... ....... 4.0 14 ... ....... 13 108 ...... 345 ...... 7.7 ......
840-124-6 2-2 5-84 ...... ...... 08 32 ....... ...... ...... 103 200 ............. 040 370 ...... 1,630 ...... 7.0 ..

Elder spring .......... 2,8 0.00 8.4 1.0 1.8 ...... 1 1 4.1 8 ...... 4.8 8as 29 11 ..... ...... 0.4 ..
Heath
Spring... 4- 0-52 0.8 .10 .8 1.2 7.0 0.2 6 1.0 12 0.0 .3 40 7 ...... 60 1 5.0 ..
Sanlando
Springs... 4-23-40 13 .09 29 7.9 5.8 .0 125 3.3 8 .2 .1 123 105 ...... 228 0 7.2 ..






REPORT OF INVESTIGATIONS No. 27


wells driven into the Pleistocene sand yield water containing an objec-
tionable amount of iron.
CALCIUM
Calcium (Ca) is. dissolved from limestone, shells, and coral, which are
composed largely of calcium carbonate. Calcium imparts the property of
hardness to waters in the county. The concentrations of calcium in 170
ground-water samples ranged from 14 to 326 ppm.
MAGNESIUM
Magnesium (Mg) is dissolved from most rocks but especially from
dolomite and dolomitic limestone, which contain large amounts of mag-
nesium carbonate. As limestones in central Florida contain small amounts
of magnesium carbonate, magnesium is usually found in much smaller
quantities than calcium. Magnesium and calcium are the two major con-
stitutents causing hardness in natural waters.
Magnesium is one of the principal constituents of sea water and it
is found in relatively large quantities in ground water contaminated with
sea water. The magnesium content of 170 ground-water samples from
Seminole County ranged from 0.5 to 441 ppm.

SODIUM AND POTASSIUM
Sodium (Na) and potassium (K) are dissolved from many rocks, but
because sea water is composed mainly of a solution of common salt (so-
dium chloride), large amounts of sodium are usually associated in Florida
with ground water that has been contaminated with sea water or indus-
trial wastes. The sodium content may be 5 to 20 ppm in ordinary ground
water or more than several hundred ppm in a highly mineralized water.
The potassium content is generally relatively small. Waters that contain
only a few ppm of sodium are likely to contain about equal quantities
of potassium. As the amount of these constituents increases, the propor-
tion of potassium becomes less.
The sodium content in 23 ground-water samples in Seminole County
ranged from 4.7 to 730 ppm, and the potassium content in 17 ground-
water samples ranged from 0.2 to'16 ppm (table 4). This table probably
does not show the highest concentrations because the more highly miner-
alized waters were not analyzed for sodium and potassium.
Sodium is not particularly significant in drinking water except. for
those persons who require sodium-free diets. A concentration of sodium
greater than 100 ppm may cause foaming in steam boilers. Sodium may
have some effect on the permeability of some soils, particularly clayey
soils.





FLORIDA GEOLOGICAL SURVEY


BICARBONATE
Bicarbonates are common to most waters because of the abundance
of carbonate minerals in nature and because carbon dioxide, which helps
dissolve bicarbonates, is readily available. Bicarbonate, in combination
with calcium and magnesium, causes carbonate hardness.
Ground water from the Floridan aquifer in central Florida usually
contains from 100 to 300 ppm of bicarbonate. The bicarbonate content of
36 ground-water samples from Seminole County ranged from 121 of 334
ppm (table 4).
SULFATE
Sulfate (SO4) is dissolved in large quantities from gypsum (calcium
sulfate) in the rocks and soil. Sulfate is also obtained from salts in sea
water or from oxidation of iron sulfides.
Sulfate has little effect on the general use of water. The U. S.
Public Health Service (1946) recommends that the sulfate concentration
not exceed 250 ppm in drinking and culinary water on carriers subject
to Federal quarantine regulations. Sulfate in hard water contributes to
boiler scale and may have a laxative effect if present in quantities around
300 ppm. The sulfate content of 170 ground-water samples from Seminole
County ranged from 1.0 to 1,180 ppm.
CHLORIDE
Chloride (Cl) is abundant in sea water and is dissolved in small
quantities from rocks. The chloride content of ground water is generally
a reliable index of contamination by sea water because about 91 per-
cent of the dissolved solids content of sea water consists of chloride
salts. The chloride content has little effect on the use of water for ordi-
nary purposes unless it is present in large quantities.
Water from the artesian aquifer beneath most of the hilly upland in
Seminole County has a chloride content of less than 25 ppm, which might
be considered normal for this part of central Florida. Water having a
chloride content above 25 ppm suggests mixing with connate salt
water or salt water that entered the formations during higher stands of
the sea during Pleistocene time.
The chloride content of the 2,062 ground-water samples from the
county ranged from 4 to 7,950 ppm (tables 4, 5, 6). Additional chloride
analyses are shown in table 2 of Florida Geological Survey Information
Circular no. 34.
The U. S. Public Health Service (1946) recommends that the concen-
tration of chlorides not exceed 250 ppm in water on carriers subject
to Federal quarantine regulations. Water has a salty taste when the
chloride content exceeds 500 ppm, and water high in chloride is corrosive







REPORT OF INVESTIGATIONS No. 27


TABLE 5. Chloride Content of Water Samples Collected
at Various Depths in Wells

Date of Chlor- Date of Chlor-. Dateof Chlor-
Well measure- Depth ide con- measure- Depth ide con- measure- Depth ide con-
Number meant (feet) tent -ment (feet) tent ment (feet) tent
(ppm) (ppm) (ppm)

840-107-2 11-28-56 0 1,215 11-28-56 250 1,240 11-28-56 350 1,250
11-28-56 175 1,255 11-28-56 275 1,250 389 1,250
11-28-56 200 1,230 11-28-56 300 1,250
11-28-56 225 1,260 11-28-56 325 1,255
840-120-1 7-19-55 25 9 7-19-55 100 9 7-19-55 170 10
7-19-55 50 10 7-19-55 125 10
7-19-55 75 9 7-19-55 150 10
841-110-12 12- 2-56 0 1,080 12- 2-56 100 1,075 12- 2-56 200 1,025
12- 2-56 60 1,080 12- 2-56 150 1,080 12- 2-56 200 1,030
842-111-6 12- 3-56 0 960 12- 3-56 130 945
12- 3-56 75 960 12- 3-56 189 900
842-111-7 12- 3-56 0 1,300 12- 3-56 140 1,300 12- 3-56 216 1,345
12- 3-56 110 1,270 12- 3-56 180 1,275
845-117-10 7-18-55 5 70 7-18-55 150 76 7-18-55 300 73
7-18-55 50 74 7-18-55 200 73 7-18-55 335 75
7-18-55 100 75 7-18-55 250 74 7-18-55 368 75
846-116-11 7-18-55 15 320 7-18-55 50 335 7-18-55 100 335
7-18-55 30 320 7-18-55 75 330
847-113-31 12- 1-56 100 650 12- 1-56 150 650 12- 1-56 200 660
12- 1-56 125 650 12- 1-56 175 660 12- 1-56 240 675
848-116-12 7-19-55 10 415 7-19-55 175 380 7-19-55 300 380
7-19-55 50 415 7-19-55 200 380 7-19-55 325 380
7-19-55 100 390 7-19-55 225 380 7-19-55 350 380
7-19-55 125 380 7-19-55 250 380 7-19-55 380 380
7-19-55 150 380 7-19-55 275 380 .......... ........





REPORT OF INVESTIGATIONS No. 27


surface represents a composite of the chloride content of water
obtained from all the producing zones within the well.

QUALITY OF WATER.
The wide range in the chemical composition of ground water in Semi-
nole County is shown by analyses of samples of the water. Some of the
ground water is excellent for ordinary use and some cannot be made
suitable for general use by any practical treatment.
The amount of dissolved mineral matter in water from the Floridan
aquifer ranges from low in the recharge areas of the hilly uplands to high
in the discharge areas of the lowlands. Stubbs (1937, p. 27) concluded
that the highly mineralized water in Seminole County was coming from
the Coskinolina Zone (Avon Park Limestone). Information collected
during this investigation has shown that the area in which the well is lo-
cated is more important in regard to the dissolved solids content of water
than the geologic formation that the well penetrates.
Samples of ground water for chemical analyses were collected in every
section of the county, but the most intensive sampling was done in
the areas. in which the water is highly mineralized. These areas gener-
ally include most of the areas of artesian flow. The chemical analyses were
made by the Quality of Water Branch of the U. S. Geological Survey.
The dissolved chemical constituents of water are reported in parts per
million (ppm). A part per million is a unit weight of a constitutent in a
million unit weights of water. Thus, a water sample containing 1 ppm of
iron (Fe) contains 1 pound of iron in a million pounds of the water sam-
pled. In order to show water analyses graphically, the cations and anions
may be expressed in chemically equivalent weights or equivalents per mil-
lion (epm); parts per million may be converted to equivalents per million
by dividing the parts per million by the combining weight of the respec-
tive cation or anion. Specific conductance is reported in reciprocal ohms
mhoss); pH is reported in standard pH units; and color is reported in
dimensionless units defined by the standard platinum cobalt scale.
The mineral constituents of natural waters generally reflect the com-
position and solubility of the rock materials with which the waters have
been in contact. In Seminole County, the minerals found in ground water
are not obtained entirely from rocks and soils. Some of the mineralization
of ground water in Seminole County probably comes either from sea
water that entered the rocks during the interglacial periods of the
Pleistocene Epoch, or from sea water that was trapped in the rocks when
they were deposited.






66 FLORIDA GEOLOGICAL SURVEY


TABLE 6. Chloride Content of Water That Was Collected
as Wells Were Being Drilled

Date of Chlor- Date of Chlor- Date of Chlor-
Well measure- Depth ide con- measure- Depth ide con- measure- Depth ide con-
Number ment (feet) tent ment (feet) tent ment (feet) tent
(ppm) (ppm) (ppm)

837-103-1 4- 7-56 90 12 4- 7-56 105 17 4- 9-56 136 13
4- 7-86 95 15 4- 7-56 110 16 4- 9-56 145 13
4- 7-56 100 12 4- 9-56 124 14 4- 9-56 154 13
4- 7-56 103 14 4- 9-56 130 14 4- 9-56 158 15
837-103-2 4-27-56 85 26 5- 7-56 142 78 5-30-56 184 80
4-27-56 90 25 5- 7-56 153 80 5-30-56 186 80
4-27-56 94 27 5- 7-56 157 79 5-30-560 190 80
4-27-56 100 26 5- 7-56 157 78 5-30-56 197 85
4-27-56 104 27 5-30-56 146 69 5-30-56 204 80
4-27-56 104 28 6-30-56 148 65 5-30-56 210 80
4-27-56 104 72 5-30-56 151 73 5-31-56 216 73
4-27-56 105 74 5-30-56 153 73 5-31-56 224 75
4-30-56 105 60 5-30-56 155 74 5-31-56 230 78
4-30-56 105 62 5-30-56 156 74 5-31-56 238 80
4-30-56 105 66 5-30-56 160 77 5-31-56 244 78
4-30-56 105 67 5-30-56 164 73 5-31-56 251 83
4-30-56 106 70 5-30-56 167 77 5-31-56 257 84
4-30-56 106 70 5-30-56 170 74 5-31-56 265 83
5- 7-56 108 75 5-30-56 171 77 5-31-56 270 73
5- 7-56 115 78 5-30-56 172 80 5-31-56 272 72
5- 7-56 124 77 5-30-56 177 80 6- 1-56 273 80
5- 7-56 130 77 5-30-56 181 80
841-11O-9 12-28&-52 106 640 12-31-52 130 645 1- 1-53 156 700
842-111-6 1-12-53 65 450 1-22-53 135 710
1-20-53 80 560 1-27-53 200 755
843-104-13 12- 8-56 60 590 12- 8-56 61 600 12-29-56 62.3 710
12- &-5e 60 600 12-29-56 62 705 12-29-56 62.5 715
12- 8-56 61 600 12-29-56 62.2 700
845-117-8 5- 8-56 159 50 5- 8-56 164 48 5-9-56 180 49
5- 8-56 160 48 5- 8-56 172 48 5- 9-56 187 51
5- 8-56 161 48 5- 8-56 177 49 5- 9-56 190 49
5- 8-56 163 51 5- 8-56 178 49 5- 9-56 191 47
846-115-15 6-25-56 115 26 6-26-56 145 30 6-26-56 165 90
6-25-56 130 30 6-26-56 155 27 6-26-56 185 31
847-116-8 5-12-52 93 280 5-12-52 120 275 5-13-52 160 280
5-12-52 104 280 5-13-52 160 280
847-116-9 5-19-52 84 290 5-20-52 155 300 5-20-52 206 310
5-19-52 107 295 5-20-52 187 310
847-117-14 11-16-55 84 370 11-17-55 109 480 11-17-55 144 480
11-16-55 90 370 11-17-55 119 480 11-17-55 144 460
11-17-55 91 480 11-17-55 130 480 11-18-55 147 480
11-16-55 92 470 11-17-55 140 470 11-18-55 151 470
11-17-55 100 500 11-17-55 143 470






REPORT OF INVESTIGATIONS No. 27


to boilers and plumbing. A chloride content of more than 800 ppm is
harmful to some irrigated crops (Westgate, 1950, p. 116-123).
FLUORIDE
Fluoride (F) is dissolved from soil and rocks, but the quantity in
natural waters is generally very small. Fluoride concentrations of 34
ground-water samples from Seminole County ranged from 0.0 to 0.4 ppm.
Excess fluoride in water is associated with the dental defect known
as dental fluorosis (mottled enamel) if children drink the water habitu-
ally during the formation of their permanent teeth. Recent studies have
concluded that a fluoride concentration of 0.75 to 1.5 ppm has a bene-
ficial effect on teeth by reduction of the incidence of dental caries
(decay).
NITRATE
Nitrate (NO8) is a relatively unimportant constitutent of most waters
in Florida. Fertilizers may add nitrate directly to water resources. The
presence of high nitrates suggests possible pollution by human and ani-
mal wastes. The nitrate concentration of 20 samples of ground water
from Seminole County did not exceed 5 ppm. This small concentration
has little effect on the use of water for ordinary purposes.

DISSOLVED SOLIDS
The residue of a water, on evaporation, consists of the mineral ma-
terials reported in the analyses. A small quantity of organic material
or water of crystallization is sometimes included. The amount of dis-
solved solids found in 170 ground-water samples from Seminole County
ranged from 80 to 13,900 ppm. Water that has less than 500 ppm of dis-
solved solids is usually satisfactory for domestic use. Water that has more
than 1,000 ppm of dissolved solids is likely to have enough of certain
constituents to produce a noticeable taste or make the water undesira-
ble for many uses.
The dissolved solids content of water was used by Krieger, et al.,
(1957) to classify the degree of salinity of highly mineralized waters.
The divisions used in this publication are as follows:
Description Dissolved solids (ppm)
Slightly saline 1,000 3,000
Moderately saline 3,000 10,000
Very saline 10,000 35,000
Brine 35,000+
According to this classification, ground water in Seminole County can be
classed as fresh (not saline) to very saline.
Figure 81 shows the dissolved-solids content of water from artesian
wells in the county. The dissolved-solids content of the ground water is






FLORIDA GEOLOGICAL SURVEY


less than 500 ppm in all the hilly uplands. This area extends from the
towns of Lake Monroe and Paola south to Orange County, and from
Chuluota and Oviedo west to Orange County. An approximately circular
area around Geneva is included also. Ground water having a dissolved-
solids content of 500 to 1,000 ppm occurs in a relatively narrow band
between the hilly uplands and the level lowlands. Ground water having
a dissolved-solids content of 1,000 to 3,000 ppm occurs in some lands
adjacent to Lake Monroe, Lake Jessup, and the Econlockhatchee River.
The highest concentration of dissolved solids was in ground water ad-
jacent to the St. Johns River, north and east of Geneva. A small area
between Geneva and Oviedo contains ground water also very high in dis-
solved solids.
HARDNESS
The hardness of water is most commonly recognized by high soap
consumption. It is caused by compounds of calcium and magnesium.
These compounds also are active in the formation of scale in steam boilers.
There are two types of hardness in water-carbonate hardness and
noncarbonate hardness. Carbonate hardness is that caused by calcium
and magnesium bicarbonate. Most of this type of hardness can be re-
moved by boiling or by treatment with lime. Noncarbonate hardness is
caused primarily by sulfates, chlorides, and nitrates of calcium and
magnesium and is more difficult to remove.
Water that has a hardness of less than 60 ppm may be rated as soft,
and treatment for removing hardness is justified for few purposes. Hard-
ness between 60 and 120 ppm may be classed as moderately hard, but
does not interfere with the use of water for most purposes. Hardness
between 120 and 200 ppm may be classed as hard and some form of
softening is usually required for many industrial uses. Hardness above
200 ppm may be classed as very hard and is objectionable for most
industrial and domestic uses.
The hardness of 170 ground-water samples from Seminole County
ranged from 62 to 2,630 ppm as CaCO, (table 4). The hardness of water
from the Floridan aquifer in Seminole County is shown in figure 32, which
shows that ground water from the hilly uplands is softer than ground
water from the level lowlands. The water has a hardness between 60 and
120 ppm in a large area between Paola and Longwood, and in smaller
areas west of Altamonte Springs, southwest of Oviedo, east of Chuluota,
and around Geneva. Ground water in the remaining areas of the hilly
uplands has a hardness of 121 to 200 ppm. Ground water having a hard-
ness of over 200 ppm occurs in most of the area adjacent to the St. Johns,
Econlockhatchee, and Wekiva rivers and in the areas adjacent to Lake
Jessup, Lake Monroe, and Lake Harney. The hardness of ground water







REPORT OF INVESTIGATIONS No. 27


exceeds 500 ppm in an area surrounding both sides of the northern half
of Lake Jessup, and encircling the 4- to 6-mile area of lower hardness that
surrounds Geneva. This area extends southward along the St. Johns
River into Orange County.
HYDROGEN SULFIDE
Hydrogen sulfide (H112S) is found in most artesian water in Seminole
County. This gas has a very distinct taste and odor which has caused
the water to be called sulfur water. Hydrogen sulfide in ground waters
is probably caused by the bacterial reduction of sulfates, by water cir-
culating through iron sulfide, and resulting from organic matter. It may
usually be removed by aeration or by allowing the water to stand in an
open container.
The amount of hydrogen sulfide in 15 samples of ground water ranged
from 0.6 to 24 ppm (table 4). A strong odor is imparted by less than 1
ppm of H112S in water. The amount of hydrogen sulfide differs consider-
ably within Seminole County.
HYDROGEN-ION CONCENTRATION
The hydrogen-ion concentration of a water is a measure of the degree
of acidity or alkalinity. This concentration is reported as pH. A pH of 7.0
represents neutrality, which means that the water is neither acid nor alka-
line. A pH higher than 7.0 indicates increasing alkalinity and a pH lower
than 7.0 indicates increasing acidity.
Most ground waters from the Floridan aquifer are slightly alkaline
and the pH usually ranges from 7.0 to 8.0. In Seminole County, the pH
of 163 artesian water samples ranged from 7.2 to 8.5 (table 4). The pH
of water from shallow wells driven in the Pleistocene sands are usually in
the acidic range from about 5.0 to 7.0. Water with a pH of less than
7.0 is likely to be more corrosive than water with a pH higher than 7.0.
CHEMICAL CHARACTER OF GROUND WATER
Figure 33 shows bar graphs of the 3 principal cations and 3 principal
anions, in equivalents per million (epm) in water from 20 artesian
wells and 3 springs in Seminole County. The water of low dissolved-
solids content is of calcium bicarbonate type; as the dissolved-solids con-
tent increases, the water becomes of sodium chloride type. The sum of
the cations and anions in artesian well water ranged from 2.29 to
46.50 epm. This upper range is not the maximum limit because the most
highly mineralized water was not sampled. The analyses of water from
two springs that obtain their water from Pleistocene sand showed that
they contained 0.45 and 0.66 epm, which is a very small amount of
dissolved minerals. The water from the only artesian spring sampled
contained 2.36 epm and is of calcium bicarbonate type.






FLORIDA GEOLOGICAL SURVEY


V i __ __'" ._




c a ------- a W x W-


7 0 W 0 x cc




Figure 3:3. Bar graphs of the chemical analyses of water from 20 artesian wells
and 3 springs.






The increase in chemical constituents with increased distance from
the recharge area is shown in figure 84, and shows that the chloride
content increases most. The concentration of chloride increased almost
30 times from well 845-114-6, near the recharge area, to well 845-114-5,
and more than 80 times from well 845-114-6 to well 845-118-11. The sum
of the sodium and potassium ions increased from 0.5 to 28 epm.
Calcium is the principal cation in well 845-114-6, near the recharge
area, and there is not enough magnesium to plot; the magnesium con-
tent in well 845-114-5 is more than one-half the calcium content; and
the magnesium exceeds calcium in well 845-113-11. Most of the calcium
is probably dissolved from the limestone formations and most of the
magnesium probably comes from sea water that has not yet been flushed
from the aquifer. (See the following section.) The sulfate content in-
creased only slightly as compared to the above constituents. Bicarbonate
is the only principal ion that decreased away from the recharge area.







REPORT OF INVESTIGATIONS No. 27


2 tMINULt L.UUUNITY
- 25 Map showing approximole location of wells _
EXPLANATION -

Sod"m and ChR. W Xd

g M xx
2 0Pofoloum Bc oa


dsc Collfom Bicarboethare
o1 0




0 025 0.50 0.75 1.00 1.25 1.50
DISTANCE, IN MILES FROM APPROXIMATE CENTER OF RECHARGE AREA

Figure 84. The relationship of the chemical constituents in ground water to the
distance of the wells from a recharge area centered near Golden and Silver lakes.


SALT-WATER CONTAMINATION
Salty water is present in the Floridan aquifer in many parts of Florida.
Although salty water could result from several causes, in Seminole County
it appears to be the result of the infiltration of sea water into the
aquifer during the Pleistocene time, when the sea stood higher than at
present. Since the last decline of sea level, fresh water entering the
aquifer has been slowly diluting and flushing out the salty water. Water
samples collected from wells of different depths in the northern
and central parts of the county show that flushing has progressed further
in the upper part of the artesian aquifer than in the lower part. One of
the most serious water problems facing the county is the danger that
withdrawals from the upper part of the aquifer will cause water from
the lower zones to move upward and contaminate the water in the upper
part of the aquifer.
The last extensive stand of the sea over Florida was the Pamlico
sea, which occurred during the mid-Wisconsin Glacial Stage of the





FLORIDA GEOLOGICAL SURVEY


Pleistocene Epoch. This sea stood approximately 25 feet above present
sea level and inundated about half of Seminole County (fig. 35).
Figure 35 is a map of Seminole County showing the relationship of the
Pamlico shoreline (at 30 feet above sea level) and the 250 ppm isoch-
lor. (An isochlor is defined as a line on a map connecting points at which
the chloride content of ground water is equal.) This figure shows a
definite relationship between the 250 ppm concentration of chloride in
the artesian water and an altitude of 30 feet above sea level. Almost all
the wells that yield water having a high chloride content are in areas -
where the land surface is less than 30 feet above sea level.
Analyses of samples from more than 700 wells show that the chloride
content from the upper part of the Floridan aquifer ranges from 4 to
7,950 ppm. Several samples of water having a chloride content of 4.0
ppm were collected from wells near Paola, southwest of Lake Jessup, and
in the area southeast of Lake Mary. The water having the highest
chloride content was collected from a well at Mullet Lake Park, near
the St. Johns River. The general results of these analyses are shown in
figure 36. As may be seen from the figure, water from the Floridan
aquifer beneath most of the hilly upland has a chloride content of less
than 25 ppm. The relatively low chloride content of the artesian water
in the hilly upland is probably due to the fact that this is a recharge
area for the Floridan aquifer. Another reason for the low chloride con-
tent of the artesian water in this area may be that the last inundations
from the ocean covered only the land at a lower altitude.
The low chloride content of artesian water in local recharge areas was
first noted by Stringfield (1936,.pl. 16) in his investigation of the artes-
ian water in the Florida Peninsula. After making subsequent investiga-
tions in Seminole County and mapping the chloride content of the
artesian water in the county (V. T. Stringfield, unpublished map in files
of U. S. Geological Survey), he concluded that the low chloride content
in the Geneva area was a result of flushing by local recharge (R. C.
Heath, oral communication).
The areas in which the artesian water contains more than 25 ppm
chloride include the northeastern half of the county (except for the hilly
upland around Geneva) and a narrow belt along the valleys of the
Wekiva and Little Wekiva rivers (fig. 36).
Water that has a chloride content ranging from 26 to 250 ppm is
suitable for drinking, irrigation, and most industrial uses. A chloride con-
tent of more than 250 ppm exceeds the amount generally recommended
for a municipal water supply. Areas in which the chloride content of
ground water exceeds this limit include: a thin band from the Wekiva






REPORT OF INVESTIGATIONS No. 27


River eastward to the St. John's River, the area adjacent to Lake Monroe
on both sides of Sanford and extending around the north side of Lake
Jessup, a small area 2 miles south of Sanford, a thin band circling Geneva
and extending along part of the Econlockhatchee River, and an area
northeast of Oviedo (fig. 86).
Ground water that has a chloride content ranging from 1,000 to 5,000
ppm is unsuitable for drinking, many industrial uses, and for the irriga-
tion of most crops (Westgate, 1950, p. 116-128). Areas in which such
ground water occurs include land adjacent to the Wekiva and St. Johns
rivers in the northwest corner of the county, a very small area 2 miles
northwest of Sanford, most of the land adjacent to the northwestern part
of Lake Jessup, a semicircular area north of Geneva, and an area south-
east of Geneva (fig. 86).
Water containing more than 5,000 ppm of chloride is almost unus-
able for any purpose. Such ground water is obtained from a small area
extending from Mullet Lake northeast along the St. Johns River, and an
area south of Lake Harney (fig. 36).
Chemical analyses of water samples collected periodically, coinci-
dent with measurements of artesian pressure, indicate that the chloride
content of the artesian water may vary with changes in artesian pressure.
Figure 87 illustrates changes in the chloride content and the water level
of three wells south of Sanford. This figure includes data collected by
Stringfield, 1986, Stubbs, 1987, and Irving Feinberg in 1939 (personal
communication) as well as data collected during the present investiga-
tion. The graphs for well 845-113-1, 4.8 miles southeast of Sanford, illus-
trate the effect of water-level changes in the chloride content of the
water from 1953 through 1956. The chloride content was lowest when
the water level was highest during the latter part of 1953. After this
date the water level declined as a result of decreased rainfall and the
chloride content increased. The chloride content increased approximately
250 ppm during the period of record. In order to show what effect the
period of flow prior to collecting the water sample had on the chloride
content of the water, symbols were used in figure 37 to show different
periods of flow. The period of flow apparently had little effect on the
chloride content of the water from well 845-113-1.
The graphs for well 844-116-1, 5.8 miles south of Sanford, indicate no
relation of the chloride content of the water to changes in the water level.
The graphs show a decrease of about 100 ppm of the chloride content
during the 20-year period of record, with decline of water level of ap-
proximately 1 foot during normal rainfall years.
The graphs for well 844-114-1, 4.4 miles south-southeast of Sanford,







74 FLORIDA GEOLOGICAL SURVEY


1,300 m

--- -,--


fi,- CHLORIDE CONTENTq
Well 845-113-1.4.1 miles southeast of Snor
29

218-

/ -
S27











t2 z3- --r -~- --
4 24 V,
WATER LEVEL
23

1 _CHLORIDE CONTENT
ui 600--- -- ^^ -- --- --t
600

S500 well 844-116-1, 53 miles south of Sanford

36











:'. -- -- -- -'
35 -- -

z 34-

S33-

32

31 3
WATER LEVEL
30

S S goo, --- --- --- --- --- ---
j- 7I* 51n flowing for indeflnte p.
z i* Wll floing For live minute
0 100 -4

b600 --
^ LI CHLORIDE CONTENT
0 5003 Well 844-114-1, 4.4 miles south-southeost of S
31
p.-> 30-

'-< 29-

28
p- 27
27 ----- E LE

26- -
WATER LEVEL
25 152-1 553


Figure 37. Hydrographs and chloride content of water from wells 844-114-1,
844-116-1, and 845-113-1.






REPORT OF INVESTIGATIONS No. 27


show some correlation of the chloride content of the water to changes in
the water level. The chloride content increased about 150 ppm from 1937
to 1954 with a corresponding decline in the water level of about 1 to
1/ feet. An indefinite period of flow prior to sampling seems to give a
slightly higher chloride content than a 5-minute period of flow.
Graphs of water level and chloride content of the water in three wells
west of Sanford are shown in figure 38. Well 849-119-3, 0.4 mile west of
Lake Monroe, shows that the chloride content varied considerably during
the period of record. This change in the chloride content bears some
relation to the change in the water level, but the most important factor
seems to be the period of flow prior to sampling. Since 1951 the chloride
content had been less than 79 ppm when the well was sampled after
flowing only 5 minutes. When the well was sampled after flowing long-
er than 5 minutes, the chloride content of the water ranged from 65 to
290 ppm. This amount of fluctuation would tend to mask any progres-
sive trend in the chloride content. During the dry period of May 1939,
the chloride content of the water was almost 250 ppm. The change in
water level from 1937 and 1939 to 1956 seems to indicate a decline of
about 1 foot during the period of record.
The graph for well 848-117-8, 1.9 miles west of Sanford, shows close
correlation of the chloride content of the water to changes in the water
level. The chloride increased about 150 ppm from 1937 to 1954 with a
corresponding decline in the water level of about 19 feet. In addition,
many of the high water levels during the years 1952-56 correspond to
low chlorides.
The graph for well 848-116-2, 0.4 mile west of Sanford, shows very
little correlation of changes in the water level with changes in the
chloride content. The vertical permeability must be relatively low near
this well. The water level declined 6 feet from 1953 to 1956 and the
chloride content did not change any significant amount.
Figure 39 shows the graphs of the chloride content and water level
for two wells about 2.5 miles northeast of Oviedo. Although the wells
are only 600 feet apart, they show considerable differences in both the
water level and the chloride content. Well 841-110-12 is 213 feet deep
and is cased to 58 feet. Well 841-110-9 is 156 feet deep and is cased to
53 feet. In January 1953 the level in the deeper well was about 8
feet above that in the other well. The chloride content in the deeper
well was about 370 ppm higher than in the other well. In December
1956, the water level in the deeper well was only about 2 feet above
the water level in the other well, and the chloride content was only 185
ppm higher than that of the other well. The fact that both the water






FLORIDA GEOLOGICAL SURVEY


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Well flowing for indefinie period
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I .CHLORIDE CONTENT
U S Well 848-116-2. 0.4 mile west of Sonford-<









tWATER LEVEL
1 1935 1937 1939 1951 1952 1953 1954 1955 1956

Figure 38. Hydrographs and chloride content of water from wells 848-116-2,
848-117-8, and 849-119-3.






REPORT OF INVESTIGATIONS No. 27


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24WELL 841-110-9, 2.5 MILES NORTHEAST OF OVIEDO

S'o WATER LEVEL


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1953 1954 1955 1956


Figure 39. Hydrographs and chloride content of water from wells 841-110-9 and
841-110-12.

level and the chloride content of water from these two wells are ap-
proaching each other indicates the upper and lower water may be mix-
ing. The usually effective confining bed may be penetrated by the bore
hole of the deeper well. The water level in well 841-110-12 fluctuated
through a range of 12 feet-the largest fluctuation measured in Seminole
County during the investigation.
Graphs shown in figure 40 illustrate the chloride content of the water
and the water level for two more wells in Seminole County. Well 846-
112-5 is 4.2 miles southeast of Sanford and well 842-112-1 is 2.3 miles
north of Oviedo. In general, figure 40 shows the significant changes that
are seen on most graphs for wells in the two areas. Near Sanford, the
water levels have remained about the same or declined slightly since
1939. The decline in water levels is probably due to an increase in


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FLORbA GEOLOGICAL SUVwEY


Figure 40. Hydrographs and chloride content of water from wells 842-112-1 and
846-112-5.
pumping in the area. The chloride content of the water shows more
fluctuation in the Sanford area than around Oviedo. This can probably
be attributed to an effective confining layer of dense limestone in the
Oviedo area that retards the upward movement of salty water from
below.
The hydrographs for wells around Oviedo indicate a decline in the
water level of about 2 to 8 feet since 1939. This decline can be attributed
to the increased use of water in the area near Oviedo.
Figure 41 presents data from four wells in the county. These data
include information on the water level, chloride content of the water,
temperature of the water, and yield of the well. In general, the graphs
for these four wells show a very close relationship of the changes in
water level and changes in yield of the well (subject to slight errors
of measurement), but little change in temperature of the water, and
little correlation of changes in the water level with changes in the



















































Figure 41. Data from wells 842-110-2, 843-108-4, 845-113-10, and 848-113-1.


PRfotjoT oF INVESTIGATIONS No. 27






FLORIDA GEOLOGICAL SURVEY


chloride content of the water. The temperature of water from these flow-
ing wells is almost constant during the year.
The data for the graphs plotted in figure 42 were collected in 1933
by V. T. Stringfield, in 1937 by S. A. Stubbs, and in 1939 by Irving
Feinberg, and during the present investigation. The data are again used
to compare measurements made in the past to those made more recently
in order to observe any trends. The graphs for these three wells show
information similar to the data given in figure 41.
The graphs for well 849-117-1, 1.7 miles northwest of Sanford, show
little correlation between the changes in chloride content to changes in
the water level. The chloride content increases about 100 ppm after
the water flows for a long period which suggests that salty water may
be moving up from deeper formations. An inspection of the water-
temperature graph indicates an annual fluctuation of about 3F. How-
ever, the variation reflects soil temperature because the well outlet is
offset and the water travels through a horizontal pipe located about 1
foot below the surface. The water level in well 841-111-1, 1.8 miles north-
east of Oviedo, has fluctuated as much as 15 feet during 1937-56 and as
much as 11 feet during December 1953 to February 1954. The chloride
content has remained almost constant during 1937-56. The water level
in well 841-110-1, 2.6 miles northeast of Oviedo, has declined about 3
feet during 1951-56 while the chloride content has increased slightly
during the period.
QUANTITATIVE STUDIES
The principal hydraulic properties of an aquifer are its capacities to
transmit and store water, for all aquifers serve as both reservoirs and
conduits. The Floridan artesian aquifer acts primarily as a conduit, trans-
mitting water from recharge areas toward discharge areas; however,
some of the water is yielded by compression of the aquifer material and
the water.
The coefficient of transmissibility is a measure of the ability of an
aquifer to transmit water. It is the quantity of water, in gallons per day,
that will flow through a vertical section of the aquifer 1 foot wide and
extending the full saturated height of the aquifer, under a unit hydraulic
gradient, at the prevailing temperature of the water. The coefficient of
storage is a measure of the capacity of an aquifer to store water, and is
defined as the volume of water released from or taken into storage per
unit surface area of the aquifer per unit change in head normal to that
surface.
The withdrawal of water from an aquifer creates a depression of the
water level in the vicinity of the point of withdrawal. This depression








REPORT OF INVESTIGATIONS No. 27


Figure 42. Data from wells 841-110-1, 841-111-1, and 849-117-1.


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Figure 43. Flow-measuring apparatus (a, well valve with 4-inch discharge pipe; b,
4-inch dresser coupling; c, 9-inch fitting to measure; d, quick-closing
valve; e, 4-inch pipe, 4 feet long; f, l-inch piezometer tube; g, 4-inch
by 2U-inch orifice; h, staff gage and tube to measure artesian pressure).






REPORT OF INVESTIGATIONS No. 27


has the approximate form of an inverted cone and is referred to as the
cone of depression. The distance the water level is lowered at any given
point within this cone is known as the drawdown at that point. The size,
shape, and rate of growth of the cone of depression depend on several
factors, including (1) the rate of pumping, (2) the transmissibility and
storage capacities of the aquifer, (3) the increase in recharge resulting
from the lowering of the water level, and (4) the decrease in natural
discharge due to the lowering of the water level.
A portable apparatus was constructed to measure the discharge of
flowing wells and is shown in figure 43. This apparatus consisted of a
4-foot length of 4-inch diameter pipe, threaded at both ends, having a
calibrated orifice fitting at one end of the pipe. The other end of the
pipe was attached to a 3-inch valve by a 4-inch reducing coupling and
a 3-inch nipple. "Dresser" couplings in 2-, 3-, and 4-inch sizes, together
with appropriate pipe fittings, were used to connect the equipment to
the discharge pipe of a flowing well.
In order to cover different ranges of flow two calibrated orifices were
made from a 4-inch pipe coupling that was cut in half, and a plate of
stainless steel was welded to each of the two pieces. A sharp-edge orifice
opening was machined from the plates to exact diameters of 2D2 and
3 inches. The 232-inch orifice was used to measure flows ranging from
50 to 180 gpm and the 3-inch orifice was used to measure flows ranging
from 100 to 300 gpm.
In order to open or close the flow rapidly a gate valve was machined
and changed to a quick-closing valve operated by a lever. A %-inch hole
was tapped in the center of the pipe, 2 feet from the orifice, and a
piezometer tube consisting of a 5-foot length of clear plastic hose was
connected to the hole. Another li-inch hole was tapped in the nipple
used between the valve and dresser coupling, to measure the artesian
pressure in the well when the valve was closed. A long piece of clear
plastic hose was connected to this opening.
The results of eight recovery tests made by using this portable appa-
ratus are shown on table 7. The table shows that the coefficients of
transmissibility differ considerably throughout the county. The average
of the coefficients of transmissibility determined from the 8 tests was
164,000 gpd: per foot. If the transmissibility determined from the test
at well 841-110-9 is not used, the average coefficient of transmissibility
is 185,000 gpd per foot. Well 841-110-9 penetrates only a few feet of the
aquifer, which accounts for the very low coefficient of transmissibility.
A sample plot of the recovery data for well 841-113-8 is shown in






FLORIDA GEOLOGICAL SURVEY


TAmBL 7. Data From Recovery Tests of Artesian Wells in Seminole County
Transmis- Specific
sibility- Yield of Diameter Time of capacity
Well (gpd per well of well test (gpm per
number foot) (gpm) (inches) (minutes) foot) T/Sp.C.
838-114-8 253,000 96 4 60 22 12,000
841-110-9 9,100 40 4 60 8 1,100
841-113-3 98,000 26 2 90 3 33,000
842-110-7 223,000 50 3 90 8 29,000
843-118-4 315,000 68 3 120 13 24,000.
845-113-1 82,000 68 3 75 8 11,000
847-112-7 193,000 44 2 20 4 47,000
849-118-5 134,000 71 4 40 12 11,000


figure 44. The formula used to determine the coefficient of transmissibil-
ity was the time-drawdown method of Cooper and Jacob (1946, p. 526-
264 Q
535), stated as T = where:
aS
T=coefficient of transmissibility in gpd per foot
Q=yield in gpm
AS--difference in drawdown (or recovery) over one logarithmic cycle


A short aquifer test was made in August 1955 of well 845-113-15.
The well was allowed to flow at 60 gpm for a period of 18 hours.
Measurements of the artesian pressure were made periodically on well
845-113-16,25 feet from the flowing well during the test.
The observed data for well 845-113-15 were analyzed by the Theis






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a,^ A O g ,. s a w too AM --M M --- o 04M
,MUM. IM P, MuMON *M.L
Figure 44. Semilog plot of recovery versus time in well 841-113-3.






REPORT OF INVESTIGATIONS No. 27


graphical method, as described by Wenzel (1942, p. 87-89). This method
involves the following formula, which relates the drawdowns in the
vicinity of a discharging well to the rate and duration of discharge:
0o
114.6Q e-u du 114.6Q W(u)
s- du= W(u)
T u T

u
-U

where u = 1.87r'S
Tt
s = drawdown, in feet, at distance r and time t
r = distance, in feet, from pumped well
Q = pumping rate, in gpm
t = time since pumping began, in days
T = coefficient of transmissibility, in gpd per foot
S = coefficient of storage, a dimensionless ratio
The formula is based on certain assumptions, which include the
assumptions that the aquifer is of uniform thickness, of infinite area
extent, and is homogeneous and isotropic (transmits water with equal
ease in all directions). It is assumed also that there is no recharge to
the formation or discharge other than that from the one well within
the area of influence of the well, and that water may enter the well
throughout the full thickness of the aquifer.
114.6 Q
Inserting the values in the formulas T= 114.6 W(u) and S =
uTt
------ gives a transmissibility of 51,000 gpd per foot and a storage
1.87r2
coefficient of 0.000004. Data collected and analyzed from well 845-113-1
(table 7), located 150 feet away from well 845-113-15, show a value of
82,000 gpd per foot for the transmissibility. This value was calculated
using the time-drawdown method. These values do not represent the
transmissibility of the entire artesian aquifer as they are drilled only a
relatively short distance into the artesian aquifer. Deeper wells would
draw from a greater thickness of the aquifer and would, consequently,
show higher values.
Values of coefficients of storage for artesian conditions in other areas
range from about 10-4 to about 10-3. The value of 4 x 10-6 obtained in
this test is very small. However, Jacob and others (1940, p. 44) state
that when the ratio of the lateral distance between the observation well
and the pumped well to the depth of aquifer is small, the value of the
computed, storage coefficient is likewise small. Also, it is known that
the values of storage coefficient obtained during short periods of pumping
are comparatively small and that during prolonged pumping the