Interim report on ground waters resources of the northeastern part of Volusia County, Florida ( FGS: Information circular 8 )

STATE OF FLORIDA
STATE BOARD OF CONSERVATION
Ernest Mitts, Director

FLORIDA GEOLOGICAL SURVEY
Herman Gunter, Director

INFORMATION CIRCULAR NO. 8

INTERIM REPORT

ON

GROUND WATERS RESOURCES
OF
THE NORTHEASTERN PART
OF
VOLUSIA COUNTY FLORIDA

By

GRANVILLE G. WYRICK And WILLARD P. LEUTZE

PREPARED BY U. S. GEOLOGICAL SURVEY
IN COOPERATION WITH THE FLORIDA GEOLOGICAL SURVEY
AND THE CITIES OF
DAYTONA BEACH, NEW SMYRNA BEACH AND PORT ORANGE

Tallahassee, Florida
1956

CONTENTS

Page

Abstract.....................
Introduction ..................
Previous Investigations .........
Geography ....................
Geology............... ....
Test Drilling..... ...........
Form nations .... ........ ....
Avon Park Limestone .........
Ocala Group ...............
Miocene or Pliocene Deposits. .

Pleistocene and Recent Deposits

Ground Water..........
Water-table Aquifer .....
Artesian Aquifer .......
Quality of Water .....
W ells....... .. ...
Salt-water Contamination .
Quantitative Studies ....
Construction and Location
Observation Wells ...
Pumping Test. .......
Analysis of Data .......
Summary and Conclusions.
References ............

* .

of Test

* .
. .

. .

...

and

...
. .
. .
. .
. .

ILLUSTRATIONS

Figure Page
1. Map of Volusia County showing principal
municipalities and area covered by the
report. ..... .. .... ..... 12
2. Map showing locations of test wells. . 15
3. Graphs showing data obtained from test
well SW -5 ................... .. 17
4. Graphs showing data obtained from test
well SW -1 .................. .... 18
5. Graphs showing data obtained from test
well NE-1 .... ................. 19
6. Graphs showing data obtained from test
well NE-2 ............. .. 20
7. Generalized geologic sections showing the
formations penetrated by wells in the
northeastern part of Volusia County. ... 21
8. Section along line A-A' in figure 7 showing
the height of the water table, the artesian
pressure head, and the direction of
movement of artesian water in March 1955 27
9. Hydrographs of wells 25 and 31 in Volusia
County and the monthly rainfall at
Daytona Beach. . . . ..... 33
10. Map of northeastern part of Volusia County
showing areas of artesian flow . ... 35
11. Map of northeastern part of Volusia County
showing the wells sampled for chemical
analyses . . . . . ... .. 37
12. Map of northeastern part of Volusia County
showing the distribution of wells that
have been inventoried ............... 39
13. Map of northeastern part of Volusia County
showing the chloride content of water
from the upper part of the artesian
aquifer, 1954 .... ... . ... .. 45
14. Section along line A-A' in figure 7 showing
the chloride content of water in the
artesian aquifer, 1955. . . .... 48

Figure

15. Map showing the chloride contend of water
from the artesian aquifer in the vicinity
of the Adams Street well field, Daytona
Beach ................. .. ........... 50
16. Graph showing the chloride content of
water from the Port Orange city wells. 51
17. Hydrographs of the pumped well and
nearby observation wells during the
pumping test . . . . .. 57
18. Hydrographs of the observation wells
during the pumping test.. . . .. 58
19. Graphs showing fluctuations of the water
table, drainage ditch, and barometric
pressure during pumping test. . .... 59
20. Log plot of the drawdowns and first part
of the recovery versus t/r2.. . 62
21. Semilog plot of drawdowns versus t/r2 for
well SW-4-A showing solution for
transmissibility and storage coefficients .64
22. Graph showing predicted drawdowns in
the vicinity of a well pumping 1,000 gpm
for selected periods of time . . ... 67
23. Theoretical drawdowns after 1 year of
pumping a group of wells at a rate of
9,000 gpm . ........ . . 68
A. Drawdowns in the vicinity of a
group of nine wells ....... ...... 68
B. Drawdowns in center well of a
line of wells. ............... 68

Page

TABLES

1. Population of incorporated municipalities in
the northeastern part of Volusia County,
1920-1950 . . ... ............
2. Analyses of water samples from wells in
northeastern Volusia County . .
3. Breakdown of selected artesian wells in
northeastern Volusia County showing
relationship between diameter and use
and diameter and depth . . ...
4. Records of test wells in the northeastern
part of Volusia County.. . . ..

... 40-41

... 54

Table

Page

GROUND WATERS RESOURCES
OF
THE NORTHEASTERN PART OF VOLUSI A COUNTY

FLORIDA

By
GRANVILLE G. WYRICK And WILLARD P. LEUTZE

Volusia.County comprises an area of 1, 207 square miles
in the central part of the east coast of Florida. This report
covers the northeastern third of the county. Limestone
underlies this area beginning at a depth of 50 to 100 feet
below the land surface and extending to a depth of several
thousand feet. The upper part of the limestones includes the-
Avon Park limestone of late middle Eocene age and the Ocala
group 1/ of late Eocene age. The Ocala group is overlain

1/ The stratigraphic nomenclature used in this report
conforms to the usage of the Florida Geological Survey. It
conforms also to the usage of the U. S. Geological Survey
with the exception of the Ocala group and its subdivisions.
The Florida Survey has adopted the Ocala group as described
byPuri (1953). The Federal Survey regards the Ocala as a
formation, the Ocala limestone.

by sediments composed of sand, clay, and shells of Miocene
or Pliocene age. These sediments are overlain in turn by
Pleistocene and Recent sand deposits, which blanket the area
ito a depth of approximately 30 feet.

FLORIDA GEOLOGICAL SURVEY

Ground water in the northeastern part of Volusia County
occurs under both water-table and artesian conditions. The
water-table aquifer, composed of sand beds of Pleistocene
and Recent age and the uppermost sand and shell beds of
Miocene or Pliocene age, generally furnishes sufficient
water for domestic use. The aftesian aquifer is composed
of limestone of Eocene age. Beds of relatively impermeable
clay of Miocene or Pliocene age overlie the limestones of
Eocene age and confine the water in them. Numerous thin
beds of low permeability retard the vertical movement of
water between the highly permeable zones of the artesian
aquifer. The artesian aquifer supplies most of the ground
water used in the northeastern part of Volusia County.

The records of water levels indicate that there has been
no progressive lowering of water levels in the artesian aqui-
fer. Water levels decline locally during periods of heavy
pumping, but they recover during periods of low pumping.

Salt-water contamination of the artesian water occurs
where fresh water in the aquifer is underlain by salt water
and heavy pumping lowers the artesian pressure in the fresh-
water zones sufficiently to cause the salt water to move up-
ward. The encroachment may be prevented by developing
wells only in areas where salt water lies at a considerable
depth or by avoiding large drawdowns.

A pumping test made 6 miles west of Daytona Beach in-
dicates that the upper zones of the artesian aquifer have
a storage coefficient of 0.0007 and a transmissibility of
300, 000 gpd/ft. Salt water in the test area occurs at a depth
greater than 500 feet and numerous layers having low perme-
ability intervene between it and the fresh water in the upper
zones of the aquifer. The test indicates that, if drawdowns
in the fresh-water zones of the aquifer are not excessive,
salt-water contamination probably will not occur.

INTRODUCTION

The problem of actual or potential salt-water contami-
nation of fresh ground-water supplies is present in many

FLORIDA GEOLOGICAL SURVEY

Ground water in the northeastern part of Volusia County
occurs under both water-table and artesian conditions. The
water-table aquifer, composed of sand beds of Pleistocene
and Recent age and the uppermost sand and shell beds of
Miocene or Pliocene age, generally furnishes sufficient
water for domestic use. The aftesian aquifer is composed
of limestone of Eocene age. Beds of relatively impermeable
clay of Miocene or Pliocene age overlie the limestones of
Eocene age and confine the water in them. Numerous thin
beds of low permeability retard the vertical movement of
water between the highly permeable zones of the artesian
aquifer. The artesian aquifer supplies most of the ground
water used in the northeastern part of Volusia County.

The records of water levels indicate that there has been
no progressive lowering of water levels in the artesian aqui-
fer. Water levels decline locally during periods of heavy
pumping, but they recover during periods of low pumping.

Salt-water contamination of the artesian water occurs
where fresh water in the aquifer is underlain by salt water
and heavy pumping lowers the artesian pressure in the fresh-
water zones sufficiently to cause the salt water to move up-
ward. The encroachment may be prevented by developing
wells only in areas where salt water lies at a considerable
depth or by avoiding large drawdowns.

A pumping test made 6 miles west of Daytona Beach in-
dicates that the upper zones of the artesian aquifer have
a storage coefficient of 0.0007 and a transmissibility of
300, 000 gpd/ft. Salt water in the test area occurs at a depth
greater than 500 feet and numerous layers having low perme-
ability intervene between it and the fresh water in the upper
zones of the aquifer. The test indicates that, if drawdowns
in the fresh-water zones of the aquifer are not excessive,
salt-water contamination probably will not occur.

INTRODUCTION

The problem of actual or potential salt-water contami-
nation of fresh ground-water supplies is present in many

INFORMATION CIRCULAR NO. 8

areas of Florida. This problem is especially serious in
coastal areas where direct encroachment from the ocean is
possible or where salt water occurs at relatively shallow
depths in the water-bearing formations. It has become acute
in certain coastal areas of Pinellas County and parts of the
Miami area of Dade County.

During recent years the cities of Daytona Beach, Port
Orange, and New Smyrna Beach, in the northeastern part of
Volusia County, have experienced problems of salt-water
contamination as a result of the increased use of ground
water. The increased use of ground water is due to both an
increase in per-capita use of water and a rapid growth in
population. Recognizing the problems, the City Council of
Daytona Beach requested the U. S. Geological Survey to
make an investigation of the ground-water resources of
Volusia County. In response to this request, an investiga-
tion was begun in October 1953 by the U. S. Geological
Survey in cooperation with the Florida Geological Survey
and the cities of Daytona Beach, Port Orange, and New
Smyrna Beach.

The purpose of the investigation is to make a detailed
study of the geology and ground-water resources of the
county, with special emphasis on the problems of salt-water
contamination. This report reviews the progress of the
investigation through June 1955. The major phases of the
investigation include the following:

1. Inventory of existing wells to determine their number,
location, depth, distribution, diameter, yield and other
pertinent data.

2. Drilling of test wells in selected areas where infor-
mation cannot be obtained from existing wells.

3. Chemical analyses to determine the chemical charac -
ter of the ground water.

4. Collection and study of water-level records to deter-
mine the seasonal fluctuations and progressive trends.

FLORIDA GEOLOGICAL SURVEY

5. Geologic studies to determine the character and ex-
tent of the various geologic formations.

6. Determination of the water-transmitting and water-
storing capacities of the different water -bearing formations.

The investigation was made under the immediate super-
vision of Ralph C. Heath, Acting District Geologist, and
Jack T. Barraclough, Hydraulic Engineer, and under the
general supervision of A. N. Sayre, Chief of the Ground
Water Branch, U. S. GeologicalSurvey, and Herman Gunter,
Director of the Florida Geological Survey.

Previous Investigations

The geology and ground-water resources of Volusia County
are discussed in several reports published by the U. S.
Geological Survey and the Florida Geological Survey.

Cooke (1945, p. 226-227, 272, 311) briefly discusses the
occurrence of the Caloosahatchee marl, Anastasia forma-
tion, and Pamlico formation in Volusia County. A report
by Vernon (1951, figs. 13, 33, and pl. 2) includes Volusia
County in generalized maps of central Florida which show
generalized geologic sections and the structure of the Inglis
member of the Moodys Branch formation.

The ground-water resources of Volusia County have been
briefly studied in connection with larger, more generalized
investigations. A map of the piezometric surface of the
principal artesian aquifer in Florida (Stringfield 1936, pl. 12)
includes Volusia County. Stringfield (1936, p. 152, 162-163)
also discusses the areas in which the artesian aquifer is
rechargedand areas in which the chloride content of artesian
water is low in Volusia County. Stringfield and Cooper
(1951, p. 71) discuss the occurrence of salty artesian water
in eastern Volusia County.

Chemical analyses of water from wells in Volusia County
are included in a report byCollins and Howard (1928, p. 130-
133) and a report by Black and Brown (1951, p. 109-110).

INFORMATION CIRCULAR NO. 8

GEOGRAPHY

Volusia County occupies an area of 1,207 square miles
in the central part of the east coast of Florida (see fig. 1).
The area covered by this report includes the northeastern
third of the county (see fig. 1). The three largest cities in
the area of the report are Daytona Beach, New Smyrna
Beach, and Ormond. Other incorporated municipalities in
the area are Holly Hill, South Daytona, and Port Orange.

The mean temperature in Volusia County is about 71* F,
according to the records of the U. S. Weather Bureau. The
normal annual rainfall at Daytona Beach is about 51 inches.
The precipitation is greatest during early falland least dur-
ing late spring.

The total permanent population. of the northeastern part
of the county is probably about 50, 000. The population of
the incorporated municipalities in the area from 1920 to
1950 is shown in table 1:

Table 1.

Population of incorporated municipalities in the
northeastern part of Volusia County, 1920-50.
(Source: Reports of U. S. Bureau of the Census)

Municipality 1920 1930 1940 1950

Daytona Beach 825 16,598 22,584 30,187
Holly Hill 332 1, 146 1,665 3, 232
New Smyrna Beach 2, 007 4,149 4,402 5,775
Ormond 1,202 1,517 1,914 3,418
Port Orange 380 .678 662 1,201
South Daytona 571 692

Total 4,746 24,088. 31,798 44,505

FLORIDA GEOLOGICAL SURVEY

* PIERSON

DLLY HILL
DAYTONA BEACH

ORANGE

ORANGE CITY

+ ALAMANA

# ENTERPRISE

Figure 1 -

Map of Volusia County showing principal
municipalities and area covered by the
report. Inset map shows location of the
county.

61
-4%

0
0r

5 0 5
SCALE IN MILES

INFORMATION CIRCULAR NO. 8

The topography of Volusia County consists of terraced
lowlands and hilly uplands. Terraced lowlands occur over
all the northeastern part of the county except a small area
at the southwestern corner of that part. They consist of
three essentially level surfaces (terraces) within the follow-
ing altitude ranges: sea level to 10 feet; 20 to 30 feet; and
40 to45 feet. Each terrace is separated from the next high-
er one by a scarp--a rather abrupt rise in the land surface.
The nearly level surfaces of the terraces are modified in
the vicinity of the coast by sand ridges. The easternmost
ridge, which U. S. Highway 1 follows, is only a few hundred
yards west of the Halifax River. The second and larger
ridge is about a mile and a half west of the Halifax River.

The hilly uplands consist of low, rolling sandhills and
numerous small lakes. Many of the lakes were formed by
the collapse of the surface deposits into caverns formed by
solution of the underlying limestone. Altitudes in the up-
lands range from 40 feet to about 75 feet above sea level.

The surface drainage of the area is poorly developed,
resulting in relatively large swampy areas. The principal
streams in the area are the Tomoka River and Spruce Creek
which flow eastward into the Halifax River, which is not a
river but a lagoon that runs parallel to the coast throughout
most of the northeastern part of the county. The Halifax
River and its southern counterpart, Mosquito Lagoon, are
connected to the ocean by Ponce de Leon Inlet. This inlet
is the only break in the offshore bar in Volusia County.

Most of the land in northeastern Volusia County is not
used for agriculture. However, there are small farms and
citrus groves along the coast and a truck-farming area at
Samsula, 8 miles west of New Smyrna. Beach. Large parts
of the area are devoted to the production of timber and beef
cattle and dairy products.

FLORIDA GEOLOGICAL SURVEY

GEOLOGY

Test Drilling

An important phase of the investigation was the construc-
tion of test wells to obtain information that could not be ob-
tained from existing wells. The U. S. Geological Survey
drilled 9 test wells along U. S. Highway 92 between Daytona
Beach andDeland (see fig. 2). During drilling, the following
were collected:

1. Rock cuttings at approximately 5-foot intervals.

2. Information on the length of time required to drill
each layer of the limestone formations.

3. Water samples for chloride analyses at intervals of
5 to 10 feet (from the bailer).

4. Water samples from isolated sections of the well.

5. Water-level measurements representing both the com-
posite pressure head in the entire open hole and the
head in isolated sections of the well.

Upon completion of the wells, traverses were made with
a current meter to locate the water-producing zones and to
determine the rate of internal flow in the wells. Also, water
samples were collected at different depths using a deep-well
sampler.

The test wells were numbered according to their direc-
tion and distance from the well that was pumped during the
pumping test. Thus, well SW-1 is the first well southwest
of the pumped well (PW) in figure 2. Upon completion of the
drilling and current-meter traverses, three of the wells
were altered so that measurements of the water levels could
be made in isolated parts of the aquifer. A suffix was added
to the number, at that time, indicating to which aquifer or
parts of the artesian aquifer the well was open. To wells
penetrating only the water-table aquifer, the suffix "S" was
added. Wells open to the upper part of the artesian aquifer

Figure 2 Map showing location of test wells.

FLORIDA GEOLOGICAL SURVEY

were indicated by the suffix "A", and wells open to one or
more of the lower zones of the artesian aquifer were indi-
cated by the suffix "D".

The most important information obtained from the wells
is shown diagrammatically in figures 3, 4, 5, and 6.

Formations

The geology of northeastern Volusia County is described
on the basis of rock cuttings collected from 103 wells and
of a study of the topography. The rocks older than the Avon
Park limestone are not described in this report because no
water wells in the area are known to penetrate them.

Avon Park Limestone

The Avon Park limestone (Applin and Applin, 1944), of
late middle Eocene age, is the oldest deposit exposed at the
surface in any part of Florida. It crops out in Citrus and
Levy Counties. In an area known as the "Sanford High"
(Vernon, 1951, p. 57), which centers around Orange City,
the Avon Park is the first limestone penetrated by wells.
The top of the Avon Park in northeastern Volusia County
dips gently eastward from the Sanford High, and is overlain
by younger limestones of Eocene age in nearly allthe report
area (see fig. 7).

The color of the Avon Park limestone ranges from chalky
white to light brown or ashen gray. Most of it is some shade
of tan. Some beds, especially near the top of the formation,
are composed of a loose coquina of cone-shaped Forami-
nifera, small echinoids (Peronelladalli), and shells of other
marine organisms. The Avon Park limestone is almost in-
variably dolomitized in northeastern Volusia County (see
columnar sections on figs. 3, 4, 5, and 6). The process of
dolomitization (replacement of some of the calcium of lime-
stone by magnesium) often changes the permeability of a
bed. The change depends on the original form of the lime-
stone and on the mode of dolomitization. If the rock was
originally a loosely packed, coquina limestone, dolomitiza-
tion generally renders it dense and less permeable. Other
beds of dolomite are extremely porous, having a spongy,

z
-n

0
Z

O
)a

O

'O

aD

Figure 3 Graphs showing data obtained from test well SW

Figure 4 Graphs showing data obtained from test well SW-1.

Figure 5 Graphs showing data obtained from test well NE-1.

Figure 6 Graphs showing data obtained from test well NE-2.

Eli II II II II I ~fS^ z

ar toee 0

*PLEISTOCENE AND RECENT

S1UPPERl MIOCENE Op PLIOCENE r

WW OCALA OUP
esI

ii ---^-------------- ---- i "
CMM

AVON PARK LIMESTONE

WAgOt M MLLU

Figure 7 Generalized geologic sections showing the formations penetrated by wells
in the northeastern part of Volusia County.

FLORIDA GEOLOGICAL SURVEY

"honeycomb" appearance, due to selective dolomitization of
matrix rock. The Avon Park includes dolomite of both these
types. A third type of dolomitized rock found in this forma-
tion is a chalky, pasty mass, containing crystals of dolomite
as fine as silt.

A distinctive bed composed of large cone-type Forami-
nifera, especially Dictyoconus gunteri, was penetrated by
three of the test wells. Many specimens have a diameter of
6 mm or more. Vernon 2/ has identified this bed as part

2/ Vernon, R. O., personal communication, June 1955.

of his "Zone B" of the Avon Park (Vernon, 1951, p. 98).

The thickness of the Avon Park limestone in Volusia
County is unknown. Well SW-1 (see fig. 4) penetrated more
than 325 feet of the formation. The formation is probably
of about the same thickness in Volusia County as it is in
Seminole County, where Heath and Barraclough (1954, p. 12)
report it to be nearly 500 feet thick. The top of the Avon
Park was eroded before the overlying Ocala group (of Puri,
1953) was deposited, and on the crest of the Sanford High
the formation was again eroded before beds of the upper
Miocene or Pliocene were deposited.

One of the most notable features of t'e Avon Parkand the
overlying limestones is the presence of dense, indurated
beds. These beds are readily detectable during drilling be-
cause they greatly retard the drilling rate. This can be seen
onthe graphs of drillingtime onfigures 3, 4, 5, and 6, which
show that sections ranging from 5 to 10 feet thick required
15 minutes or more per foot of drilling. The section from
235 to 245 feet in well SW-1 (see fig. 4) is one of the most
conspicuous in this respect.

Information collected during the drilling and testing of the
wells indicates that these dense zones are relatively imper-
meable. Therefore, wherever these layers are continuous
for a considerable distance they greatly retard upward or
downward movement of water between the different perme-
able zones.

INFORMATION CIRCULAR NO. 8

A study of the relative-resistivity graphs on figures 3,
4, 5, and 6 shows that most of the dense layers also have a
fairly high resistivity. Thus, it may be possible in the later
phases of the investigation to trace the more prominent dense
layers through the use of resistivity logs.

Chemical analyses of water from different depths in the
same well show that the hardness of water from isolated
sections of the Avon Park limestone is less than that of water
from the overlying limestone. This may be due to the fact
that dolomite, which makes up a relatively large part of the
formation, is less soluble in water than limestone.

The Avon Park limestone is the principal source of arte-
sianwater in the western part of the report area, where the
Ocala group of Puri (1953) is thin or absent. Also, many
of the deeper wells along the coast draw part of their water
from the Avon Park.

Ocala Group

The upper Eocene unit known elsewhere as the Ocala lime-
stone 3/ was established by Puri (1953) as a group composed

3/ Cooke, 1945, p. 53; Applin and Jordan, 1945, p. 130;
Vernon, 1951, p. 115, 118; Puri, 1953, p. 130.

of three similar formations. The first two were namedby
Vernon(1951), who, however, did not retain the name Ocala.
These are, in ascending order: the Inglis, the Williston,
and the Crystal River formations. All three are fragmental
marine limestones which are differentiated on the basis of
fossil content and lithology.

In central and western Florida, where the Ocala group
crops out, its three formations have a different lithology and
contain distinctive faunas. In Volusia County, where data on
the rocks must be obtained from well cuttings, the forma.-
tions generally cannot be separated (Vernon, .1951, p. 122,
144 and 157). The upper part, the Crystal River formation

FLORIDA GEOLOGICAL SURVEY

of Puri (1953) has not been recognized in northeastern
Volusia County, and was probably removed throughout the
county by post-Eocene erosion (Vernon, 1951, pl. 2; Neill,
1955, fig. 4).

The Inglis formation, in its typical development, is a
coarsely granular marine limestone containing abundant
echinoid fragments. Of these, pieces of Periarchus lyelli
are the most readily identifiable and are found only in this
formation. The color of the rock is cream to creamy white,
mottled with gray. The gray color is due to finely divided
iron sulfide. The bottom part of the formation contains re-
worked fragments of the Avon Park limestone, which it over-
lies with an angular unconformity. The thickness of the
formation averages about 50 feet (Vernon, 1951, p. 118) but
may be as much as 120 feet in some parts of the county
(Vernon, 1951, p. 121-122). The Inglis is overlain by Vernon's
Williston formation. The Inglis formation has been removed
from the crest of the Sanford High and has been thinned by
erosion in most, if not all, of the remainder of the county.
The Inglis formation is very porous and permeable and yields
a large part of the water used in the northeastern part of
Volusia County.

The Williston formation as used by Vernon (1951) is a
soft granular marine limestone. It is generally finer grained
than the Inglis, and contains fewer echinoid plates. Some of
its beds consist of a loosely cemented mass of Foraminifera.
The lithology of the Williston indicates that it was deposited
in deeper water than the Inglis, which is essentially a beach
or shallow sea deposit. The Williston averages about 30 feet
in thickness, but it has been entirely eroded from the western
part of the report area and thinned by erosion throughout the
rest of the area. Owing to its finer texture, the Williston is
less permeable than the Inglis. Nevertheless, it is an im-
portant part of the artesian aquifer in eastern Volusia County.
Along the coast, many wells draw exclusively from this for-
mation, but deeper wells draw also from underlying beds.
The hydrologic properties of both the Williston and the Inglis
may be modified locally by dolomitization. The combined
thickness of the two formations reaches a maximum of ap-
proximately 90 feet along the eastern coast of Volusia County
(see thickness of Ocala group in fig. 7).

INFORMATION CIRCULAR NO. 8

Miocene or Pliocene Deposits

The unconsolidated beds of fine sand, shells, and calcare-
ous silty clay which overlie the artesian aquifer were clas-
sified byCooke(1945,p. 214, 226-227, and pl. i) as theCaloo-
sahatchee marl of Pliocene age. Vernon (1951, figs. 13 and
33, and personal communication, June 29, 1955) indicated that
these beds were of late Miocene age. In Volusia County they
generally consist of a basal shell bed overlain by calcareous
clay, fine sand, and silty shell beds. As the permeability of
these beds is relatively low, they serve to confine water
under pressure in the artesian aquifer. The basal shell bed
yields a small amount of water and hence some wells are
left open to it. These wells sometimes pump sand.

Pleistocene and Recent Deposits

Sediments of Pleistocene and Recent age blanket the
northeastern part of Volusia County. Their contact with the
underlying deposits is marked by a bed of coarse sand grains,
waterworn shells, and, occasionally, a combination of these
materials cemented together by calcium carbonate. The
Pleistocene and Recent deposits are chiefly fine- to medium-
grained quartz sand, locally mixed with shells. In many
parts of the county the sediments are stained yellow or
orange by iron oxide. Locally, the sand has been cemented
into "hardpan" by deposition of iron oxide at the water table.

The Pleistocene and Recent deposits yield small quanti-
ties of water to shallow wells. They are an important source
of water in those areas in which the artesian water is too
salty for domestic use. Many wells draw from these deposits
in the area from Ormond to New Smyrna Beach.

GROUND WATER

Ground water is the water that is in the zone of satura-
tion--the zone in which all pore spaces arefilled withwater
under positive hydrostatic head. The water in the zone of
saturation is derived from precipitation. Not all the pre-
cipitation soaks into the ground, however; a part evaporates

FLORIDA GEOLOGICAL SURVEY

and a part drains overland into lakes and streams. Of the
part that does filter into the earth, some is later evaporated
or is transpired by plants, and some reaches the zone of
saturation. Water that has reached the zone of saturation is
available to supply springs and wells and is referred to as
ground water.

Water in the zone of saturation moves laterally under
the influence of gravity toward a place of discharge, such as
a spring or well. Where ground water only partially fills a
permeable formation, its surface, which is at atmospheric
pressure, is free to rise and fall and it, the water, is said
to be under water-table conditions. However, if ground water
completely fills a permeable formation that is overlain by
a relatively impermeable bed, its surface is not free to rise
and fall and the water is said to be under artesian conditions.
The term "artesian" is applied to such water, which is under
sufficient pressure to rise above the top of the permeable
formation containing it, although not necessarily above the
land surface.

A formation in the zone of saturation that is permeable
enough to transmit usable quantities of water to wells and
springs is called an aquifer. Areas in which aquifers are
replenished are called recharge areas. Areas in which water
is lost from aquifers are called discharge areas.

Water-Table Aquifer

Ground water occurs in Volusia County under both water-
table and artesian conditions. The water-table, or shallow,
aquifer is composed of Pleistocene and Recent sediments.
The upper portion of the deposits of Miocene or Pliocene age
also may constitute a part of the water-table aquifer in some
parts of the area. The aquifer ranges in thickness from
about 25 feet near the Halifax River to as much as 40 feet in
the central part of the area (see fig. 8).

The water-table aquifer is recharged chiefly by local
rainfall. It receives also a small amount of recharge by
upward seepage of artesianwater in the area of artesianflow

O TIO CIRCULAR VO. B

S

D~=- L --

---4-- i--t

p3
S
I

A- A' i ure 7 showing

Fgu Section al the water table th ove
gu te heigh a and the direction f

pressuates water i aC
raent Of a rte s al

FLORIDA GEOLOGICAL SURVEY

and by the downward percolation of irrigation water and the
effluent of septic tanks.

Water is lost from the water-table aquifer by natural
discharge into surface streams, such as the Tomoka River
and Spruce Creek; by discharge into the ocean; by downward
seepage into the artesian aquifer, in those areas in which the
water table stands higher than the artesian pressure head;
and by evaporation and transpiration. In addition, small
quantities of water are withdrawn from the aquifer through
wells for domestic use and lawn irrigation.

The water from the water-table aquifer is generally less
mineralized than that front the artesian aquifer. However,
in many areas water from the water-table aquifer contains
an excessive amount of iron which gives the water a dis-
agreeable taste and stains clothes and fixtures. In areas
immediately adjacent to the Halifax River and the ocean the
water-table aquifer contains salt water.

Temperature measurements of water from the water-
table aquifer ranged from 66* to 74* F. However, most of
the measured temperatures were between 68 and 70 F.

Artesian Aquifer

The artesian water of northeastern Volusia County has a
vital bearing on the economy of the area. It is used by all
communities that have public water supplies. It is the major
source of irrigation water and is used by nearly all the com-
mercial and industrial consumers that have their own wells.
It is the source for many home supplies, air-conditioning
systems, and stock wells. The current investigation of ground
water in the county is for the purpose of gathering and inter-
preting information about this valuable resource so that it
can be safely developed and wisely conserved. Most of the
information collected and studied during the investigation to
date concerns the artesian water supply.

The artesian aquifer in Volusia County consists mainly
of limestone of Eocene age. In at least a part of the county,
the aquifer includes also permeable shelly sand beds at the

INFORMATION CIRCULAR NO. 8

base of the overlying deposits of Miocene or Pliocene age.
The water in the aquifer is confined under pressure'by beds
of clay in the deposits of Miocene or Pliocene age.

Volusia County differs from most of the counties in
Florida in that most, if not all, of the freshwater in the arte-
sian aquifer is derived from rain falling on recharge areas
within the county. The hilly uplands in the central part of
the county constitute the principal recharge area. The arte-
sian aquifer receives some replenishment also in those parts
of the terraced lowlands in which the water table stands
higher than the artesian pressure head. Included in these
areas are most of the terraced lowlands above an altitude of
about 20 feet.

Figure 8 is a section showing the hydrology from well
SW-1 eastward through Daytona Beach. The upper part of
the figure shows an exaggerated profile of the land surface,
the position of the water table, the piezometric surface of
the upper part of the artesian aquifer, and the piezometric
surface of the lower part of the artesian aquifer. As may
be seen from the figure, the water table stands higher than
the artesian pressure head in all the area west of the vicinity
of the Main Canal except in a small area adjacent to the
Tomoka River. Therefore, within this area, the artesian
aquifer is being recharged by water moving downward from
the water-table aquifer through the confining bed. This down-
ward movement of water is shownby the arrows in the lower
part of figure 8.

West of the Tomoka River the pressure in the upper part
of the artesian aquifer is greater than the pressure in the
lower part. Within this area, water moves downward from
the upper part of the aquifer to recharge the lower part. As
pointed out in the discussion of the Avon Park limestone in
the section on "Geology", dense, relatively impermeable
layers of limestone were penetrated in all the test wells.
Although these layers were not penetrated at the same depth
in eachof the wells, some of the thicker layers--for example,
the layer between about 220 feet and 240 feet in wells SE-1,
NE-1, and NE-2 in figures 4, 5, and 6--appear to be con-
tinuous over large areas. Where these layers are present
f .

FLORIDA GEOLOGICAL SURVEY

they doubtless retard the downward movement of water from
the upper part of the aquifer.

In the area where the gradient is downward, where deep
wells such as SW-1 penetrate different zones of the aquifer
there is a substantial movement of water down the well bore.
This can be seen in figure 4 by comparing the relative
velocities while the well was standing idle with those while
the well was being pumped. While the wellwas standing idle,
water entered the well bore between 150 and 160 feet below
land surface, moved down the well, and entered the forma-
tions below a depth of about 225 feet. The graph of relative
velocities during pumping of the well at a rate of 143 gpm
shows an upward flow of water above 155 feet and a down-
ward flow below that depth. A comparison of the graphs
shows that the quantity of water flowing down the well bore
was reduced approximately two-thirds by the pumping.

The quantity of water moving from the upper part of the
aquifer to the lower zones through the well bore cannot be
determined from the relative velocity graphs because the
diameter of the well bore is not known. Although the open
hole was drilled with a 5-inch bit, its diameter is doubtless
somewhat greater than 5k-inches everywhere and may be a
foot or more where the well penetrated unconsolidated lime-
stone.

After water reaches the artesian aquifer it moves more
or less horizontally down the hydraulic gradient towards
points of discharge. In general, the movement of artesian
water in the northeastern part of the county is toward the
east, as indicated by the arrows in figure 8.

Water is discharged from the artesian aquifer through
submarine springs where the limestone formations outcrop
beneath the ocean, and by upward seepage through the con-
fining bed where the artesian pressure head stands higher
than the water table. Large quantities of water are also
withdrawn from the aquifer through wells. The arrows on
figure 8 indicate that upward movement of water may take
place from the artesian aquifer into the Tomoka and Halifax
Rivers. The convergence of the arrows around the Adams

INFORMATION CIRCULAR NO. 8

Street well field shows diagrammatically the effect of heavy
pumping on the movement of water in the aquifer.

East of the TomokaRiver, the pressure in the lower part
of the artesian aquifer is greater than the pressure in the
upper part (see fig. 8). Consequently, there is an upward
movementof water from the lower zones of the aquifer. How-
ever, this movement probably is not appreciable in areas
undisturbed by heavy pumping because the natural upward
gradient, which is only about 1 foot in 80 feet at wells NE-2-
(A & D), is not adequate to move large quantities of water
through the beds of very low permeability that serve as con-
fining beds between the different zones of the aquifer. In
areas of heavy pumping, as, for example, in the Adams Street
well field of the City of Daytona Beach, the pressure in the
upper part of the aquifer is drawn down by as much as 20
feet. As a result, the upward gradient in this area is many
times greater than it is elsewhere, and upward flow from the
lower zones is correspondingly much larger.

Wherever the pressure in the lower zones of the aquifer
is greater than that in the upper zones, water enters the
lower part of the open holes of wells and flows up the holes
to recharge the upper zones of the aquifer. Thus,the direc-
tion of movement of water in the deep wells east of the
Tomoka River is opposite to that in wells west of the river.
Current-meter traverses made in wells NE-1 and NE-2 after
their completion showed a large upward flow (see figs. 5 and
6). Two traverses were made in well NE-1, one while the
well was standing idle and the other while it was being pumped
at a rate of 250 gpm. A comparison of the results of the two
shows that the upward flow of water in the well while the well
was not being pumped was probably between 150 and 200 gpm.
Most of this water entered the well below a depth of 430 feet,
flowed up the well bore, and entered the lower part of the
Ocala group between the depths of 150 and 160 feet.

The graphs of relative velocities in well NE-2 (see fig.
6) show that, while the well was not being pumped, water
entered it between 395 and 485 feet. The decrease in relative
velocity between 300 and 310 feet show that a small quantity
of Water probably left the well between those depths. Most

FLORIDA GEOLOGICAL SURVEY

of the flow, however, left the well between the depths of 225
and 230 feet. The remaining flow entered the upper part of
the Avon Park limestone between the depths of 165 and 180
feet.

The collection of data on the altitude, fluctuations, and
progressive trends of water levels is an essentialpart of the
investigation. In order to determine the altitude of water
levels and pressure heads throughout the area under investi-
gation, the water levels in all open nonflowing wells and the
pressures in flowing wells are measured when the wells are
first visited. The fluctuations and progressive trends are
determined by measuring the water level in a relatively large
number of wells periodically and by maintaining continuous
recording gages on a few selected wells.

Water levels are now being observed periodically in 22
wells in Volusia County, 7 of which are equipped with record-
ing gages. Hydrographs showing the water-level fluctuations
in 2 of the wells equipped with recording gages are shown in
figure 9. Observations were begun on well 31, at Alamania,
11 miles southwest of New Smyrna Beach, in 1936. As the
water level in this wellis not affected bythe withdrawalfrom
other wells, and as the well is in the area in which the arte-
sian aquifer is being recharged, the hydrograph shows the
natural fluctuations of artesian pressure head caused by
changing rates of recharge. The heaviest rainfall generally
occurs in Volusia County from June through October. Accord-
ingly, the water level in well 31 is generally highest in the
summer or early fall. As a result of low rainfall in the
period November to May, the water level begins to decline
near the end of the year and generally is lowest in June or
July. The hydrograph for this well does not show any pro-
gressive trend, either up or down, during the 20-year period
from 1936 to 1955.

Observations of the water level in well 25, which is at
the west end of Main Street Bridge in Daytona Beach, were
begun in 1948. Thus,the record for this well is much shorter
than that for well 31. The water level in well 25 responds to
the heavy pumping in the Daytona Beach area and to seasonal
changes in the rate of recharge. The hydrograph of well 31

-J
W
-j

W
z

'J
0

u 2
P~

20-----
Monthly rainfall at Daytona Beach
15
(n
w
10

0
19361197 1937 193 9 1940 1941 1942943 1944 1945 1946 1947 1948 1949 19501951 95219531954

Figure 9 Hydrographs of wells 25 and 31 in Volusia County and the monthly rain-

fall at Daytona Beach. (Water-level records prior to 1950 supplied by

U.S. Corps of Engineers, Jacksonville, Fla.)

FLORIDA GEOLOGICAL SURVEY

shows that the natural decline of water levels during the
spring and summer for the past 4 years has been less than
it has been in other years since measurements were begun
in 1936. On the other hand, the hydrograph of well 25 shows
that the decline of water levels during the summer at Daytona
Beach has been substantially greater since 1951. This doubt-
less reflects a substantial increase in the use of ground
water at Daytona Beach.

Where the artesian pressure head stands higher than the
land surface, wells penetrating the artesian aquifer will flow.
The approximate area of artesian flow in the northeastern
part of Volusia County is shown on the map in figure 10. As
may be seen from the map, wells will flow in most of a belt
2 to 3 miles wide adjacent to the coast and in the lowlands
adjacent to the Tomoka River and Spruce Creek. Although
it could not be shown on figure 10, there is a narrow area of
artesian flow along the ocean beach.

The area of artesian flow expands and contracts in re-
sponse to seasonal changes in water levels. Thus, during
periods of low water levels, many wells cease to flow. In a
few instances, owners of intermittently flowing wells have
found that their wells will flow continuously if deepened be-
cause the pressures in the lower zones of the artesian aqui-
fer are greater than in the upper zones. In order to obtain
the full benefit of the higher pressures, it would be necessary
to case off the upper zones of the aquifer. It shouldbe noted,
however, that in most parts of the coastal area the minerali-
zation of the artesian water increases with depth. Thus, the
advantage derived from the increase in pressure resulting
from deepening a well may be more than offset by a deterio-
ration in quality of the water.

The temperature of water from the upper parts of the ar-
tesian aquifer ranges from 71to 74 F. Water from most of
the wells inventoried had a temperature between 720 and 73F.

Quality of Water

Rain, when it falls on the earth, is only slightly mineral-
ized. However, as it travels through the formations com-
posing the earth's surface it gradually dissolves them. The

INFORMATION CIRCULAR NO. 8

EXPLANATION
Area of arteslan flow
* Poll office
SPrincipol roods
1 0 I 2
.1 o lt milll

*1p

AB

-

0

YT ACH

Figure 10 Mapof northeastern part of Volusia County
showing areas of artesian flow.

\.

I

Q

t
L

INFORMATION CIRCULAR NO. 8

Miocene or Pliocene Deposits

The unconsolidated beds of fine sand, shells, and calcare-
ous silty clay which overlie the artesian aquifer were clas-
sified byCooke(1945,p. 214, 226-227, and pl. i) as theCaloo-
sahatchee marl of Pliocene age. Vernon (1951, figs. 13 and
33, and personal communication, June 29, 1955) indicated that
these beds were of late Miocene age. In Volusia County they
generally consist of a basal shell bed overlain by calcareous
clay, fine sand, and silty shell beds. As the permeability of
these beds is relatively low, they serve to confine water
under pressure in the artesian aquifer. The basal shell bed
yields a small amount of water and hence some wells are
left open to it. These wells sometimes pump sand.

Pleistocene and Recent Deposits

Sediments of Pleistocene and Recent age blanket the
northeastern part of Volusia County. Their contact with the
underlying deposits is marked by a bed of coarse sand grains,
waterworn shells, and, occasionally, a combination of these
materials cemented together by calcium carbonate. The
Pleistocene and Recent deposits are chiefly fine- to medium-
grained quartz sand, locally mixed with shells. In many
parts of the county the sediments are stained yellow or
orange by iron oxide. Locally, the sand has been cemented
into "hardpan" by deposition of iron oxide at the water table.

The Pleistocene and Recent deposits yield small quanti-
ties of water to shallow wells. They are an important source
of water in those areas in which the artesian water is too
salty for domestic use. Many wells draw from these deposits
in the area from Ormond to New Smyrna Beach.

GROUND WATER

Ground water is the water that is in the zone of satura-
tion--the zone in which all pore spaces arefilled withwater
under positive hydrostatic head. The water in the zone of
saturation is derived from precipitation. Not all the pre-
cipitation soaks into the ground, however; a part evaporates

FLORIDA GEOLOGICAL SURVEY

dissolved rock material constitutes most of the mineraliza-
tion in ground water. Thus, the chemical character of ground
water is dependent, in part, on the type of material through
which the water flows. The quartz sand that constitutes most
of the shallow aquifer in Volusia County is relatively insolu-
ble. Limestones and dolomites, which compose the artesian
aquifer, are among the most soluble of the common rocks.

The limestone, sand, and clay that underlie Volusia Coun-
ty were deposited by the ocean. When these sediments were
laid down, and when they were under the sea at later times,
they became saturated with sea water. Part of the mineral
content of the ground water in Volusia County, especially in
the coastal areas, is a result of the fact that the formations
were saturated with the salty water of the seamany millen-
niums ago.

The location of wells whose water was sampled for chem-
ical analyses during the present study are shown in figure 11.
The analyses which show the principal chemical constituents
of these samples are contained in table 2. All results given
in the table are in parts per million (ppm) unless otherwise
stated.

One part per million is a very small quantity, equal to
only 8.34 pounds of the constituent in a million gallons of
water. However, even this small quantity of certain con-
stituents, such as iron, impart objectionable characteristics
to water.

The dissolved-solids content of water is an index to the
degree of mineralization. If all the dissolved constituents
in a water sample were added together, the sum would equal
the total dissolved solids. However, because many of the
rarer constituents are not generally determined, and because
of water of crystallization, there is usually a slight discrep-
ancy between the total obtained by evaporation of a sample
and the total obtained by summation of the determined con-
stituents.

The chloride (Cl) content of water in Volusia County is
discussed in detail under the heading "Salt-water contamina-:
tion". As determinations of chloride content can be made

INFORMATION CIRCULAR NO. 8

Figure 11 -

Map of. northeastern part of Volusia County
showing wells sampled for chemical analy-
ses.

FLORIDA GEOLOGICAL SURVEY

readily in the field, this constituent is commonly used as
an index of how "salty" a water is. Water having a chloride
content of less than 500 ppm does not taste objectionably
salty to most people, and water having a chloride content of
not more than 250 ppm is acceptable for a public supply, if
otherwise satisfactory, according to the standards of the
Florida State Board of Health.

Hydrogen sulfide (HZS), a gas, imparts the taste and odor
to the water that is commonly referred to as "sulfur water".
There are several possible sources for this gas, two of which
are:

1. Decomposition of organic compounds by bacteria
under anaerobic conditions.

2. Chemical reduction of sulfates to sulfides and subse-
quent decomposition of the sulfides in the presence of carbon
dioxide.

Hydrogen sulfide has an objectionable odor, but many
people become accustomed to drinking water that contains it.
The gas can be removed from water by aeration. Analyses
of 12 samples (see "remarks" in table 2) show that where
hydrogen sulfide was present its concentration did not exceed
1.3 ppm.

The hardness of a water is caused chiefly by the basic
ions calcium (Ca) and magnesium (Mg). These constituents
are dissolved from the limestone (CaCO3) and dolomite
(CaMg(C03)2) that compose the artesian aquifer. Water
having a hardness of more than 150 ppm is rated as hard
and is commonly softened for household and certain other
uses. The hardness of artesian water in Volusia County
ranges from about 200 ppm to more than 1,000 ppm.

Wells

The inventory of wells consists of the collection of in-
formation on the location, depth, diameter, length of casing,
yield, and use of existing wells. Figure 12 shows the distri-
bution of more than 500 wells that have been inventoried in

INFORMATION CIRCULAR NO. 8

EXPLANATION

* Flowing wells
O Nonflowing wells

* Post office
- Principal roads

0
.._ __

COUNTY
col

,*

O

0

Figure 12 Mapof northeasternpartof VolusiaCounty

showing the distribution of wells that have

been inventoried.

0

o 0

o
0
0
o
o

VPP
L -z

0
o
o-o

Table 2. Analyses of water samples from wells in northeastern Volusia County

(Analyses by U.S. Geological Survey. All results are expressed in
parts per million except those for specific conductance and pH. For
locations of wells, see figure 11.)

E H C e 1 2/3/55 1- 10 448 22 1 7.
W.B. ickler ,n 127 2/3/55 1- 07 14 10 97 4542 358 881 7.3
SRE5 USGSteen 127 19407 4/8/55 198 132 90 8.6 1180 .8 0 312 2.5 860 .2 .1- 3780 1060 6070 7.2
C HW.P US loy 9 20 94 //55 1 182 17 0 2 30 171 628 354 030 7.8
ToS5 ota Ld Co. 7 4 2/2/55 -6 9 2 1 0 3 10 281 340 258 553 7.5
SH.C. Cone 165 2/3/55 87 18 -10 53 448 292 714 7.4
F WU.S. Worthingtc e 187 .2/3/55 107 16 10 67 542 3325 741 7.4
0 R Se 1 10 2/2/55 L- ~ 93 1 20- 9 3 10 127 348 268 578 7.3
$W-s USGS. 112 94. 4/8/55 19 .43 90 :8.6 15 .8 0 312 2.5 20 .2 .1 321, 260 523 7.7 Hydrogen sulfide, 0.0
SW- USGS 201 94 4/11/55 57 18 17 0 268 3.5 21 642 216 489 8.2
SW-5 UTSoS- 247 94 4/11/55 69 22 0 330 3.5 19 294 262 563 8.2
SW-5 USGS" 299 94 4/12/55 58 28 16 0 322 2.5 20 282 260 548 8.1
SW-S USGS" 351 343 4/14/55 18 1 .34 60 17 IS .5 0 248 7.2 20 .4 .2 272 220 453 7.7 Hydrogen sulfide 1.2

Aluminum, 0.18

Sw-i
SW-l
Sw-I
SW-I
SW-l

USGIS
USGS
USGS
USGS
USGS

119
289
384
496
496

102
236
377
481
102

2/9/55
2/11/55
2/17/55
2/23/55
4/15/55

24
16
16
14

1.0 126
.24 88
.83 101
.29 99
- 110

42 .5
45 1.4
32 1.0
42 1.7
28

53
82
57
122
35

500
455
435
326

356
290
302
325
316

800
754
701
829
694

102
102
102
113

5/24/55
5/26/55
5/28/55
3/17/55

15
16
17
18

.32
.05
.17
.93

366
360
365
378

28
26
26
34

.2
.2
.2
S1

382
380
380
394

296
296
297
324

632
629
631
661

7.3
7.4
7.3
7.3

Hydrogen sulfide, 0.3

Manganese, .01;

Shydrogen sulfide, u.u
E-1. SS 246 3/22/55 17 1.5 101 b 30 1.3 0 364 3. 50 .1 1 417 318 700 7.5 Manganese, .00;

hydrogen sulfide, 0.3
NE-i USGS. 360 344 3/25/55 16 3.9 70 41 49 1.7 0 274 3.8 150 .4 .1 566 343 892 7.5 Manganese, .01;

hydrogen sulfide, 0.6
NE-I USGS 435 426 3/30/55 17 .45 99 25 L23 2.2 0 284 16 255 .3 .0 792 350 1270 7.6. Manganese, .00;

Shydrogen sulfide, 1.3
NE-,I BGoB 4G 457 "4/1/55 .8 Z.5 7S 25 -.4 U z4 8.8 t 54 .2 a .-0 717 ]315 1 i 00 7.5 Manganese, .02;
S/'8 hydrogen sulfide, 0.6
NE-T. USGS 498 152 4/18/55 99 25 119 0 292 28 241 350 1330 7.4
:E-Z USGS 140 '115 3/2/55 31 .54 107 15 27 1.6 0 388 1.5 38 .4 .0 437 328 695 7.5 Hydrogen sulfide, 0.3
NE-2 USGS 265 244 3/4/55 29 1.1 101 14 21 1.0 0 352 1.2 29 .3 .0 374 310 627 7.4 Hydrogen sulfide, 0.2
NE-2 USGS 384 366 3/8/55 21 1.1 100 4.5 25 1.0 0 331 2.0 44 .2 .0 389 268 648 7.5 Hydrogen sulfide, 0.4
S.I U 5 500 489 3/ 11/55 21 1.3 55 40 20 1.6 0 307 6.0 62 .5 .0 395 302 653 7.7 Hydrogen sulfide, 0.7
NE-2 USGS 500 115 4//55 82 33 98 0 302 22 201 684 340 1110 7.6
I L.W. Tomlin 170 111 2/3/55 104 11 10 32 402 304 646 7.5
.23i Daytona Beach 19T 84 2/3/55 110 17 18 100 526 344 852 7.5
J Stanley Freeman 113 2/3/55 97 21 18 103 504 328 820 7.3
S Lews Law iZ /2/55 115 1 55 -85 592 40 512 2350 7.4
L A.B. Nordman 156 90 2/3/55 114 48 75 488 1300 480 2050 7.4
M MichaelLinkovich 116 2/3/55 39 5.5 6.0 8.0 136 120 224 7.8
N Paul Smith 150 2/3/55 110 8.1 20 44 442 308 685 7.4
0' James.Tekautz 130 105 2/3/55 106 11 15 16 368 308 605 7.3
P W.R..hipley 147 105 2/3/55 130 11 15 190 738 368 1150 7.3
Q Owen.Wood 109 2/3/55 142 56 100 744 1790 584 2910 7.3
R New Smyrna
Beach 110 2/3/55 160 127 200 1550 3360 920 5300 7.4

PW
PW .
PW
NE-1

USGS
USGS
USGS'
USGS

FLORIDA GEOLOGICAL SURVEY

the northeastern part of the county. Not shown are the many
wells inventoried in other parts of the county. About 90 per-
cent of the wells shown on figure 12 draw water from the
artesian aquifer and 10 percent draw from the water-table
aquifer. Approximately half the wells are in the area of
artesian flow.

Most water-table wells are 1 inches in diameter and 15
to 50 feet in depth. As the sediments that compose the water-
table aquifer consist predominantly of unconsolidated sands,
most water-table wells are equipped with screened drive
points.

Most artesian wells are 1 to 6 inches in diameter and
90 to 180 feet deep. Table 3 shows the relationship between
diameter and use and diameter and depth of 313 artesian
wells. As may be seen from the table, most wells for domestic
use, lawn irrigation, and stock are 1 to 2 inches in diameter.
These wells are generally constructed by driving casing to
the top of the limestone and drilling an open hole to a depth
of 25 to 50 feet below the bottom of the casing. Wells for
farm and grove irrigation, municipal supply, and air con-
ditioning are generally larger than 4 inches in diameter and
range in depth from 125 feet to 175 feet.

SALT-WATER CONTAMINATION

Saline water is present in the principal artesian aquifer
in many areas of Florida. Although the presence of saline
water could result from the several causes, in eastern Volusia
County it appears to be due to the infiltration of sea water
into the artesian aquifer during Pleistocene time, when the
sea stood higher than it is now. After the high seas of Pleis-
tocene time declined,freshwater entering the aquifer began
diluting and flushing out the salty water. It has been flushed
out of the aquifer in the recharge area in the centralpart of
the county. In areas distant from the recharge areas the
flushing is still incomplete.

More than 90 percent of the dissolved solids in ocean
water are chloride salts. Therefore, the concentration of
chloride in artesian water constitutes a reliable index to the

INFORMATION CIRCULAR NO. 8

Table 3. Breakdown of selected artesian wells in north-
eastern Volusia County showing relationship be-
tween diameter and use and diameter and depth.

Diameter (in inches)
Greater
1"-2" 21"-4" than 4" Total

Municipal and public-
supply 1 8 37 46

Commercial, industrial,
or air-conditioning 5 4 13 22

o Farm and irrigation 27 49 9 85

Domestic and lawn-
irrigation 102 9 1 112

Stock 20 8 0 28

Misc. uses 7 5 8 20

S90'-100' 18 3 5 26

" 100'-125' 71 15 3 89

A 125'-150' 58 33 4 95

SMore than 150' 15 32 56 103

Total 162 83 68 313

FLORIDA GEOLOGICAL SURVEY

degree of salt-water contamination. In Volusia County, 1,364
analyses for chloride have been made during the present
investigation to determine the chloride content of the water
in both the artesian and water-table aquifers. A map (fig. 13)
was prepared from chloride content of water from wells
penetrating the upper part of the artesian aquifer. As may
be seen from this map, the chloride content of water in the
recharge area is less than 25 ppm, indicating that flushing
is essentially complete in that area. Eastward from the re-
charge area, however, the aquifer has been flushed less and
the chloride content of the water is greater.

The two most noticeable features on the map are the two
large areas, one at the northern end of the county, and the
other in the vicinity of New Smyrna Beach, in which wells
yield water containing more than 100 ppm of chloride. In
parts of these areas wells yield water containing more than
1,000 ppm of chloride. Three smaller areas in which water
from the upper part of the artesian aquifer contains more
than 100 ppm of chloride are located in the vicinity of Daytona
Beach. Although the irregular distribution of these areas
cannot be explained from the data collected so far, they
appear to be due to either one or a combination of the follow-
ing circumstances:

1. Low permeability which retards movement of water
through the aquifer and, thus, decreases the rate of flushing.

2. Presence of faults or joints, which permit saltier
water from the lower zones of the aquifer to move upward.

3. Discharge of water from the aquifer into the Tomoka
River at the northern end of the county and into Spruce Creek
west of New Smyrna Beach. The head reduction accompany-
ing such discharge, if it exists, would result in an upward
movement of salty water from the lower zones of the aquifer.

The concentration of chloride in water samples collected
from wells of different depths indicate that the lower zones
of the artesian aquifer have been flushed less completely than
the upper zones. Thus, as a general rule, the deeper a well
is drilled the higher the chloride content of the water pro-
duced by the well. Figures 3, 4, 5, and 6 contain graphs

INFORMATION CIRCULAR NO. 8

EXPLANATION
Chloride content
(parts per million)
25 or less
26 to 100
101 to 250
11 eSt o 00oo
ID1001 or more
CALIE lW LS

Figure 13 -

Map of northeastern part of Volusia County
showing the chloride content of water from
the upper part of the artesian aquifer,
1954.

: i i:~j ::

0
O
t&h
V
l\

FLORIDA GEOLOGICAL SURVEY

showing the chloride content of water samples obtained from
the bailer during the construction of the deep test wells from
different depths in the well bore after the wells had been un-
disturbed for several weeks. The plot of the chloride content
of the bailer samples from well SW-1 in figure 4 shows a
saw-tooth effect. This effect is believed to result from the
flow of water, low in chloride content, down the well bore at
night while drilling was not in progress. Therefore, aline
connecting the highest chloride values probably would give
a fairly accurate picture of the chloride content of the water
in the different layers of the aquifer. As may be seen from
figure 4, the chloride content of the water at a depth of 497
feet was 150 ppm. After the well had been undisturbed for
several weeks, the downward flow of water of low chloride
content from the upper zones decreased the chloride content
in the lower part of the well. The high chloride content still
present in the casing apparently represents salty water that
leaked from the bailer while the lower portion of the well
was being drilled.

As pointed out in a previous section, there was an up-
ward flow of water in wells NE-1 and NE-2. Therefore, the
chloride content of the bailer samples probably represents
rather closely the actual chloride content of the water in the
producing aquifers. As may be seen from figures 5 and 6,
the chloride content in both wells began to increase at a
depth of about 250 feet. Well NE-1 reached water containing
more than 250 ppm of chloride at a depth of 435 feet, whereas
well NE-2, which is nearer the coast,drew water containing
more than 250 ppm at about 385 feet, or 50 feet less. Figure
6 shows a marked decrease in chloride content in well NE-2
below a depth of about 465 feet. A study of the data collected
during construction of the well strongly indicates that the
well penetrated a zone containing water low in chloride con-
tent at this depth. However, before the presence of such a
zone can be proved, it will be necessary to obtain substanti-
ating data from other deep wells in the area.

The chloride content of samples obtained with a deep-
well sampler from different depths in wells NE-1 and NE-2
is shown on figures 5 and 6. At the time these samples were
collected the wells had not been pumped for several days.

INFORMATION CIRCULAR NO. 8

Therefore, as may be seen from the graphs, the chloride
content was relatively high throughout the well bore as a re-
sult of the upward flow of salty water from the lower zones
penetrated by the wells.

Figure 14 is a generalized section showing the chloride
content of the water in the upper 500 feet of the artesian
aquifer along line A-A' in figure 7. As may be seen from
the figure,.the chloride content increases with depth.except
for a thin section at the top of the aquifer west of well SW-1.
Although the higher chloride content in this section cannot
be explained readily, it may be due either to low permeability,
which has retarded flushing, or to the effect of local recharge
by rainwater containing ocean spray.

The zone of relatively low chloride content that may exist
in the lower part of well NE-2 has not been shown in figure
14. If later studies show that such a zone does exist they will
probably show also that it is relatively thin and of rather
limited areal extent.

The quantity of water that maybe safely withdrawn from
the artesian aquifer in Volusia County is limited by the
extent to which the artesian pressure canbe lowered without
causing encroachment of salt water from either the sea or
the lower zones of the aquifer. Sea water, so far as is known,
has not encroached into any part of the artesian aquifer in
the county. It appears entirely likely, however, that such
encroachment would occur if the artesian pressure in the
area immediately adjacent to the coast were lowered exces-
sively by heavy pumping.

The upward movement of salty water from the lower
zones of the aitesian aquifer is the principal water-supply
problem in the coastal areas of the county. As shown in
figure 14, the depth to salty water in the aquifer is much less
in the coastal areas than in the recharge areas. Therefore,
the extent to which water levels can be safely lowered near
the coast also is less. As pointed out in the section headed
"Ground Water", the pressure in the lower zones of the aqui-
fer in the coastal areas is higher than the pressure in the
upper zones. Where the natural conditions have not been

ARTESIAN AQUIFER /

O
/ / -
_oo __ ___________- -_ *--- /._____/
8 / / /"" ""
Ngirim
*" / / / 0
S- /
S" 0 / 0
--- -/-
3' 00- /
N / r

r well EXPLArATION m

I assign ednWOfI to weIll in thie

-* 'in p"r pe million

Figure 14 Section along line A-A' in figure 7 show-
ing the chloride content of water in the
artesian aquifer, 1955.

INFORMATION CIRCULAR NO. 8

disturbed by pumping, the small difference in pressure prob-
ably results in only a small upward movement of salty water
from the lower zones of the aquifer. However, when pump-
ing begins, the difference in pressures becomes greater and
the quantity of upward flow is increased. If the pumping re-
mains constant for a relatively long period, the chloride con-
tent of the water will become stabilized at some level above
the initial concentration. If the rate of pumping is later in-
creased, the chloride content also will increase.
An increase in chloride content in response to a decline
in artesian pressure has been observed in most of the coastal
areas of the county. During the spring of 1954, the chloride
content in a well at the Riviera Hotel in Ormond Beach
increased about 50 ppm as a result of a decline in artesian
pressure of about 2 feet. Records of the Daytona Beach Water
Department show that the chloride content of water from the
Adams Street well field increases as the water level declines.
Between January and April 1954, the artesian pressure in the
vicinity of the field declined about 1 foot in response to an
increase of about 1,600,000 gallons in the average daily pump-
age rate. The average daily chloride content increased during
the same period from 132 ppm to 162 ppm.

The upward coning of salty water beneath the Daytona
Beach well field is shown diagrammatically on figure 14. A
map showing the chloride content of the water from the
individual wells in the Adams Street and a part of the Canal
well fields during a period of average pumping in February
1954 is shown on figure 15. Lines of equal chloride content
show that the area of highest chloride content was centered
around well 19 in the south-central part of the field.

The chloride content of the Port Orange city wells (see
fig. 16)has increased by as much as 50 to 75 ppm each year
since the wells were drilled in 1951. As analyses of samples
from other wells between the city well field and the coast
show no appreciable increase in chloride content during this
time, and as the chloride increase inthe center well is greater
than in the end wells, it appears that salt water has moved
upward from the lower zones of the aquifer as a result of
pumping. The rapid increase in the chloride content of the
Port Orange city well field may indicate that the zone from
which the wells draw is not effectively separated from the
lower, saltier zones of the aquifer.

Figure 15.--Map showing the chloride content of water from the artesian aquifer in
the vicinity of the Adams Street well field, Daytona Beach.

450

400

350

300

250

200

150

100

50

0

Figure 16 -

Graph showing the chloride content of water from the Port Orange city
wells.

FLORIDA GEOLOGICAL SURVEY

the northeastern part of the county. Not shown are the many
wells inventoried in other parts of the county. About 90 per-
cent of the wells shown on figure 12 draw water from the
artesian aquifer and 10 percent draw from the water-table
aquifer. Approximately half the wells are in the area of
artesian flow.

Most water-table wells are 1 inches in diameter and 15
to 50 feet in depth. As the sediments that compose the water-
table aquifer consist predominantly of unconsolidated sands,
most water-table wells are equipped with screened drive
points.

Most artesian wells are 1 to 6 inches in diameter and
90 to 180 feet deep. Table 3 shows the relationship between
diameter and use and diameter and depth of 313 artesian
wells. As may be seen from the table, most wells for domestic
use, lawn irrigation, and stock are 1 to 2 inches in diameter.
These wells are generally constructed by driving casing to
the top of the limestone and drilling an open hole to a depth
of 25 to 50 feet below the bottom of the casing. Wells for
farm and grove irrigation, municipal supply, and air con-
ditioning are generally larger than 4 inches in diameter and
range in depth from 125 feet to 175 feet.

SALT-WATER CONTAMINATION

Saline water is present in the principal artesian aquifer
in many areas of Florida. Although the presence of saline
water could result from the several causes, in eastern Volusia
County it appears to be due to the infiltration of sea water
into the artesian aquifer during Pleistocene time, when the
sea stood higher than it is now. After the high seas of Pleis-
tocene time declined,freshwater entering the aquifer began
diluting and flushing out the salty water. It has been flushed
out of the aquifer in the recharge area in the centralpart of
the county. In areas distant from the recharge areas the
flushing is still incomplete.

More than 90 percent of the dissolved solids in ocean
water are chloride salts. Therefore, the concentration of
chloride in artesian water constitutes a reliable index to the

FLORIDA GEOLOGICAL SURVEY

QUANTITATIVE STUDIES

The withdrawal of water from an aquifer causes water
levels to decline in the vicinity of the point of withdrawal. As
a result of this decline, the water table or piezometric sur-
face assumes the approximate shape of an inverted cone hav-
ing its. apex at the center of withdrawal. The size, shape, and
rate of growth of this "cone of depression" depend on several
factors. Among these are: (1) the water-transmitting and
water-storing capacities of the aquifer; (2)the rate of pump-
ing; (3) the increase in recharge resulting from the decline
in water levels; and (4) the amount of naturaldischarge sal-
vaged by the pumping. The distance that water levels are
lowered at any point by the pumping is termed "drawdown".
The drawdown is more or less proportional to the pumping
rate.

The quantity of water that may be pumped perennially
from a well or group of wells in Volusia County is limited
by the drawdown that maybe maintained without causing the
mineral content of the water to become intolerably high. In
the areas immediately adjacent to the coast, the perennial
yield is determined by the extent to which water levels may
be lowered without causing sea water to move into the aqui-
fer. In areas more remote from the coast, the yield is de-
termined by the extent to which water levels maybe lowered
without inducing an excessive upward movement of salty
water from the lower zones of the aquifer.

As the depth to salty water increases with increasing
distance from the coast, the perennialyield of awellor wells
also increases the farther the wells are from the coast.
However, the perennial yield of wells depends also on other
factors. Most important of these is the stratification of the
aquifer. As has already been pointed out, the limestone
formations that compose the aquifer consist of permeable
zones separated by thin zones of low permeability that appear
to be continuous over relatively large areas. Where zones
of low permeability underlie the fresh-water-bearing parts
of the aquifer, they retard or prevent the upward movement
of salty water. Thus, wherever such zones occur, larger
drawdowns may be maintained and the perennial yield is
larger than it otherwise would be.

INFORMATION CIRCULAR NO. 8

Other factors affecting the perennialyield of the aquifer
are recharge and discharge. Withdrawals from the artesian
aquifer in recharge areas increases the gradient between
the water-table and artesian aquifer and results in increased
recharge. Conversely, withdrawals in discharge areas sal-
vage a part of the natural discharge.

Although the principal factors affecting the yield of the
artesian aquifer in Volusia County are known, they cannot be
quantitatively evaluated with the data available at this time.
However, one phase of the current investigation was devoted
to the collection of data needed in an evaluation of the peren-
nial yield. Data pertaining to this phase were collected dur-
ing the construction of test wells along U.S. Highway 92 and
during a pumping test on well PW.

Construction and Location of

Test and Observation Wells

Three 6-inch test wells were drilled west of Daytona
Beach along U.S. Highway 92 (see fig. 2) to a depth of approxi-
mately 500 feet to determine the depth to salt water at dif-
ferent distances from the coast, the pressure head at different
depths in the aquifer, and other data. Data on these and the
other wells drilled during the investigation are contained in
table 4. Studies made during the construction of the wells
indicated that the depthto saltwater at well SW-1 was greater
than 500 feet beneath the surface. Also as this well was
found to be in a recharge area, the site appeared to be well
suited for studies of the perennial yield.

At this site an 8-inch discharge well (PW), four 2-inch
observation wells, and two 1-inch observation wells were
drilled. The 6-inch test well (SW-1) previously drilled at
the site was in effect converted into two observation wells,
ending at different depths. First a string of 2-inch casing,
perforated between depths of 416 and 496 feet, was inserted
inside the 6-inch casing. Next, a concreteplug was poured
between the 6-inch and the 2-inch casings 355 to 416 feet,
and sand and gravel were poured on top of the plug to a depth
of 234 feet (the depth of well PW). The 8-inch discharge

Table 4. Record of test wells in the northeastern part of Volusia County

SMeasuring Point

0> V 0

P-W W3535 234 10 8 30.17 Top of 8 coupling 3.13
NE-2 W-3477 500 114 6 30.55 Top of 6" coupling 2.95 16,900 NE Cement plug483'-462',
sand & gravel 462-235

,NE-2-A 235 114 6 30.55 Top of 6" coupling 2.95 16,900 E Open to upper part of NE-2
34 S 4Jl -'A u rt ** fi

NE-2-D 500 483 2 30.55 Top of 6" coupling 2.95 16,900 E Open to lower part of NE-2
I- -

SW-5-A W-3527 361 94 6 Top of 2" casing 4.00 44,000 SW
P-W W-3535 234 102 8 30.17 Top of 8" coupling 3.13
NE-1 W-3540 498 152 6 29.05 Top of 6" coupling 2.69 9,500 NE Well filled to 224
NE-1-A 224 152 6 29.05 Top of 6" coupling 2.69 9,500 NE Open to upper part of NE-i
NE-2 W-3477 500 114 6 30.55 Top of 6" coupling 2.95 16,900 NE Cement plug 483'-462',
sand & gravel 462'-235'
NE-2-A 235 114 6 30.55 Top of 6" coupling 2.95 16,900 NE Open to upper part of NE-2
NE-i-D 500 483 2 30.55 Top of 6" coupling 2.95 16,900 NE Open to lower part of NE-2
SW-S-A W-3527 361 94 6 -2 Top of 2" casing 4.00 44,000 SW
SE-3-A W-3528 235 100 2 26.84 Top of 2" casing 2.80 179 SE
SE-i-S 15 15 1I 27.03 Top of 1 casing 3.00 179 SE 3' screen point
SW-4- W-3476 496 102 6 28.92 Top of 6" coupling 1.88 25 SW Cement plug 416'-355',
sand & gravel 355'-235'
SW-I-A 235 102 6 28.92 Top of 6" coupling 1.88 25 SW Open to upper part of SW-1
SW-l-D 496 416 2 28.92 Top of 6" coupling 1.88 25 SW Open to lower part of SW-1
SW-2-A W-3539 233 100 2 28.85 Top of 2" casing 2.00 65 SW
SW-3-A W-3534 234 97 2 28.81 Top of 2" casing 2.00 179 SW
SW-3-S 15 15 14 28.87 Top of 1_" casing 3.00 179 SW 3' screen point
SW-4-A W-3532 235 102 2 29.36 Top of 2" casing 2.54 450 SW

INFORMATION CIRCULAR NO. 8

well (well PW) and the four 2-inch observation wells were
cased to a depth of approximately 102 feet and drilled as
open holes to 234 feet. The two l1-inch observation wells
(wells SW-3-S and SE-1-S) were equipped with 60-mesh
screen points and drive to a depth of approximately 15 feet
below the land surface. One 2-inch well and one 1-inch well
were constructed southeast of the discharge well. The re-
maining wells were constructed southwest of the discharge
well (see insert in fig. 2).

The discharge well was equipped with a centrifugal pump
having a capacity of approximately 2,000 gallons per minute.
Automatic water-level recorders were installed on wells NE-
1-A and SW-5-A several weeks prior to the pumping test to
establish regional water-level trends before and during the
test. Also, a microbarograph was installed at well NE-l-A
to record barometric changes during the test.

Pumping Test

In order to determine the water-transmitting and water-
storing properties of the upper part of the artesian aquifer,
a pumping test was started at 1:10 p.m. on May 24, 1955.
The test consisted of pumping well PW at a rate of 1,100 gpm
for a period of 100 hours. During the test, measurements
of the changes of water levels in the observation wells were
made periodically. In addition, changes in the water level
in the drainage ditch immediately north of the observation
wells were measured by means of a staff gage. Measure-
ments of water levels were made also in the deep 2-inch
observation well (SW-l-D) to determine how pumping from
the upper part of the artesian aquifer would effect the pres-
sure head in the lower part of the artesian aquifer. Through-
out the test, automatic water-level recorders were in opera-
tion on wells NE-l-A and SW-5-A and the microbarograph
was in operation at well NE-1-A. After the pumping was
stopped, measurements of the recovery of the water level
in each well were made periodically for 5 days.

FLORIDA GEOLOGICAL SURVEY

Analysis of Data

A tabulation of the measurements of water levels made
during the pumping test contains approximately 3,100 meas-
urements and is therefore much too lengthy to be included
in this report. However, hydrographs of each well were
plotted from these data and are presented as figures 17, 18,
and 19.

Figures 17 and 18 show a decline in water level during
the afternoon of May 23. This decline resulted from pump-
ing well PW approximately 25 minutes in order to determine
the throttle setting of the pump motor for the pumping test.
The brief rise in water levels in wells SW-1-A and SW-2-A
on May 25 (see fig. 17) resulted when the pump motor stopped
for 1 minute 40 seconds. Wells SW-l-A and SW-2-A were
the only wells measured during the time the pump stopped;
therefore this rise is not recorded on the other hydrographs.
As may be seen in figures 17 and 18, the drawdowns at the
end of the test in the pumped well (well PW) and in well SW-
4-A, 450 feet southwest of the pumped well, were about 9.5
feet and 3 feet, respectively. An indication of the extent of
the cone of depression is shownon the hydrographs for wells
NE-l-A and NE-2-A. The drawdown in well NE-l-A, 1.4
miles northeast of the pumped well, was approximately 0.9
foot. The drawdown in well NE-2-A, 3.0 miles northeast,
was approximately 0.8 foot.

In additionto the record of barometric-pressure fluctua-
tions, figure 19 contains hydrographs of shallow wells SE-
1-S and SW-3-S and the water level in the drainage ditch.
The decline of the water level in well SW-3-S on May 24 and
25 was a result of the slow drainage of water which was
poured into the well on May 23. The water level in the drain-
age ditchwas raised approximately 0.7 foot by the discharge
from the pump. As a result, the water level in well SW-3-S,
approximately 20 feet from the ditch, was held up higher than
it would have been if the ditch had not risen, as shown by the
decline that occurred on May 28 at the end of the test. How-
ever, the rise in the water table resulting from the rise in
stage of the ditch was apparently restricted to a narrow zone
adjacent to the ditch, as there was no detectable change in
the level of well SE-l-S, approximately 200 feet away.

WATER LEVEL, IN FEET, BELOW MEASURING POINT

r = A 6 6

; 0 5

I a 9 :3 5 a 71 a

m

C+
-4

(0 h
oQQ
Ed
M

CL

010
9+ 0

00 1

-~~ ~ ~ ~ ~ - -

A -_ -

- - -~ -_ -=-

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

FLORIDA GEOLOGICAL SURVEY

Figure 18 -

Hydrographs of the observation wells dur-
ing the pumping test.

11 i iiI 1I II I M L1:i: I~
6H

T '

3
0e
-i

,U
I

UL
S B.

-u
sB.
* a
0r
IU
aZ

1.1'. i I 2*Hl iiifa i 4
SIC PRESS
30.2

30.0

Figure 19 Graphs showing fluctuations of the water table, drainage ditch, and baro-
metric pressure during pumping test,

'~1 H

!Ill 17,11,

--

1 *1 T44-AIC141

~ifi ~li~Jiii i tif-it

RIIIIIIHIlki-11-1-1

It

iE 01

FLORIDA GEOLOGICAL SURVEY

In any analysis of pumping-test data it is necessary to
determine the regional trend of water levels during the test
in order to determine true drawdowns. On May 23, the first
day of the pumping test, rain occurred, which resulted in an
upward trend in water levels in the artesian aquifer. In
order to correct for this trend a comparison was made of
the hydrographs compiled prior to the pumping test for well
SW-5-A and the wells at the pumping-test site. This com-
parison showed that the water-level fluctuations at well PW
lag 3 days behind fluctuations at well SW-5-A. The draw-
downs during the pumping test were corrected by taking into
account the time lag and applying the rise in water level at
well SW-5-A to the drawdowns measured in the observation
wells. Changes in barometric pressure were found to be
relatively small during the test, and therefore no correction
was made for them.

The corrected drawdowns were analyzed by two methods
to determine the coefficients of transmissibility and storage
of the artesian aquifer. The coefficient of transmissibility,
which is a measure of the capacity of an aquifer to transmit
water, is the quantity of water in gallons per day that will
move through a vertical section of the aquifer 1 foot wide
under a hydraulic gradient of 1 foot per foot. The coefficient
of storage, which is a measure of the capacity of an aquifer
to store water, is defined by the Geological Survey as the
volume of water released from or taken into storage per
unit surface area of the aquifer per unit change in the com-
ponent of head normal to that surface.

Computations of the coefficients of transmissibility and
storage were first made using the Theis graphical method
(Wenzel, 1942, pp. 87-89). This method involves the follow-
ing formula, which relates the drawdowns in the vicinity of
a discharging well to the rate and duration of discharge:

4;

r'O

! o
0

0
rn
0
I I-

1.0
ir

KO- 10-.7 O.S lO-5 10-4 10-3

t/rg (DAYS/FEETV)

Figure 20 Log plot of the drawdowns, and first of the recovery, versus t/rZ.

INFORMATION CIRCULAR NO. 8

Inserting these values in the formulas T = 114.6QW(u) and
S
S = uTt gives a transmissibility of 310,000 gpd/ft. and a
1.87r2
storage coefficient of 7.5 x 10-4 for the upper part of the
artesian aquifer.

To check the results of the Theis graphical method, the
data from well SW-4-A were also analyzed using a method
devised by Cooper and Jacob (1946, pp. 526-534). In this
method the corrected drawdowns are plotted against the
log of t/r2 and the transmissibility and storage coefficient
are computed from the following formulas:

T = 264Q
As

S = .301T t/r2

where Q is pumping rate, in gallons per minute
As is the change in drawdown, in feet, over one
logarithmic cycle of the t/r2 scale
t/r2 is the value of t/r2 at the point of no drawdown

Aplot of the data for well SW-4-A is shown in figure 21.
Using the above formulas, the coefficients of transmissi-
bility and storage were found to be 300,000 gpd/ft. and
7.2 x 10-4, respectively.

Drawdowns in the vicinity of discharging wells penetrat-
ing the upper part of the artesian aquifer can be predicted
fairly accurately using a T of 300,000 gpd/ft, and an S of
7 x 10-4. These values do not represent the transmissibility
and storage coefficient of the entire artesian aquifer, how-
ever. As shown in table 4, the pumped well (well PW) and
nearby observation wells were drilled to a depth of about
235 feet. The wells were stopped at this depth because data
collected during constructionof wellSW-1 (see fig. 4) showed
the presence of an impermeable layer between depths of 235
and 245 feet. As an impermeable layer was penetrated at
approximately the same depth in wells NE-1 and NE-2 also
(see figs. 5 and 6), it appears that this layer is relatively
continuous and may serve as an effective hydrologic barrier

O
z

OW
IIF

MI r .. .

-0

7 1i; if ,-

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

I -

Figure 21 Semilog plot of drawdowns versus t/r2 for well SW-4-A, showing solu-
t/r2 (DAYS/FEET2)

INFORMATION CIRCULAR NO. 8

in the aquifer. If this is the case, the transmissibility and
storage coefficients determined above will represent only
the upper 150 feet of the aquifer. Deeper wells would draw
from a greater thickness of the aquifer and would, conse-
quently, show higher values.

The perennial yield of a well or wells at the pumping-
test site is limited, as in the other coastal areas of the county,
to the quantity of water that can be pumped from the aquifer
without producing drawdowns that will result in an excessive
upward movement of salty water. Water containing 150 ppm
of chloride was encountered at a depth of 500 feet in well
SW- 1, 25 feet southwest of the pumped well. Therefore, water
containing 250 ppm of chloride, the suggested upper limit
for water to be used in a municipal supply, is probably present
at a depth of less than 600 feet. In order to determine if the
drawdowns during the pumping test would result in an up-
ward movement of this salty water, water-level measure-
ments were made in well SW-l-D, which is open between
depths of 416 and 496 feet. These measurements did not
show any detectable change in water level, although draw-
downs of approximately 6 feet at well SW-l-A and 10 feet at
the pumped well were maintained for a period of 4 days. In
view of this, it appears safe to assume that, in pumped wells,
drawdowns of approximately 10 feet could be maintained
without inducing an upward flow of salty water.

In order to show the drawdowns that will result from
different rates of pumping and different well spacings, com-
putations were made using the Theis formula and coefficients
of transmissibility and storage of 300,000 and 7 x 10-4, re-
spectively. The Theis formula involves several simplifying
assumptions. Among these is the assumption that all of the
discharge is derived from storage in the aquifer. However,
after pumping begins, the downward gradient will be increased
as a result of the drawdowns produced by the pumping and
the rate of recharge will be increased. As the cone of de-
pression expands it will intersect recharge and ultimately
the recharge within the cone of depression will equal the
pumping rate. Thus, it is expected that the actualdrawdowns
during the initial.period of pumping generally would closely
approximate the drawdowns computed from the Theis formula

FLORIDA GEOLOGICAL SURVEY

but would be smaller than the computed drawdowns after the
cone of depression began to intercept recharge. It is not
possible to determine from the available data the length of
time that would be required for the cone of depression to
become stabilized. However, in similar areas in other parts
of the State, stabilized conditions have been reached within
a matter of months.

Figure 22 shows the drawdowns that would be produced
by one well discharging at a rate of 1,000 gpm for different
lengths of time. As the drawdowns outside the pumped well
vary directly with the discharge, drawdowns for greater or
lesser rates of discharge canbe computed from these curves.
For example, as shown in figure 22, under the assumed con-
ditions the drawdown 100 feet from a well discharging at
1,000 gpm would be 5.4 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 0.54 feet.

Computed profiles of the water levels in the vicinity of
several discharging wells after 1 year of pumping are illus-
trated in figure 23A. The values used to construct these
profiles were obtained by summing the drawdowns from the
1-year curve in figure 22 and applying a factor for the effi-
ciencyof the discharging wells. The factor for the efficiency
of the discharging wellwas applied to the profile only at the
discharging well, not along the entire profile. One profile
was computed for the center line of a group of nine wells
arranged in three parallel lines of three wells each, with 500
feet between lines and 500 feet between adjacent wells in each
line, forming a square grid. Each of the other profiles is
for a group of nine wells in a straight line, spaced at the dis-
tances indicated in the figure. Although the number of wells
and amount of total discharge corresponding to the four pro-
files are the same, the drawdowns are different, owing to
differences in the spacing and arrangement of the wells.

Two of the profiles in figure 23A represent drawdown
in wells 500 feet apart. In one system, the wells are arranged
in a square grid and in the other they are spaced along a
straight line. The maximum drawdownunder the grid system
exceeds the maximum drawdown under the straight-line
system by 3.5 feet. This shows that with the same number

TANCE. IN FEET. FMoW DhSCHAIINIhS WELL

-n
0

o

1,000 gpm for selected periods of time.
*i:i: :i: : : i: ::: .-

Figure 22 Graph showing predicted drawdowns in the vicinity of a well pumping
1,000 gpm for selected periods of time.

FLORIDA GEOLOGICAL SURVEY

DISTANCE, IN FEET, BETWEEN PUMPING WELLS

B. Drawdown in center well of a line of wells.

Figure 23 Theoretical drawdowns
pumping a group of wells
gpm.

after 1 year of
at a rate of 9,000

THOUSANDS OF FEET
29 20 1S 10 5 0 S 10 5B 20 25

Copulaons booed on: r I .
S 00I. 111 Onle line 'ile 560 -1"t apcoi
wmo Iwnci| |
Center lin of three lines-wells 500 fee apart
-lines 500 flet apaor
A. Orowdowns in the vicinity of a group of nine wells.

INFORMATION CIRCULAR NO. 8

of wells, discharging at the same rate, spaced at the same
distance, less maximum drawdown will result if the wells
are in a straight line.

Three of the profiles in figure 23A represent the draw-
downs resulting from straight-line well systems. In each
system, each of the nine wells is assumed to have discharged
1,000 gpm for 1 year. The maximum drawdown for each
system varies according to the distance between adjacent
wells in the system. The greatest maximum drawdown occurs
with the system having the least distance (500 feet) between
adjacent wells and the smallest maximum drawdown occurs
with the system having the greatest distance (2,000 feet)
between adjacent wells. This illustration demonstrates the
importance of well spacing in straight-line well systems.

The curves in figure 23B represent the change in draw-
down, at the center wellof straight-line well systems, as the
distance between adjacent wells is changed. The total dis-
charge of each line of wells was arbitrarily set at 9,000 gpm
and the period of discharge at 1 year. An example of the use
of this graph is as follows: If a well system were required
to yield 9,000 gpm with a maximum drawdown of 30 feet,
follow across the 30-foot drawdown line to its intercepts
withthe curves to determine the number of wells,discharge
rate for each well, and spacing between adjacent wells. The
30-foot drawdown line intersects the curve for 45 wells dis-
charging at 200 gpm each at a point corresponding to a spacing
of 400 feet. The 30-foot drawdown line intersects the curve
for 19 wells,discharging at 474 gpm each, where the spacing
is 1,150 feet between wells, and intersects the curve for 9
wells discharging at 1,000 gpm each, where the wells are
spaced 4,500 feet apart. The 30-foot drawdown line is above
the curve for 3 wells discharging at 3,000 gpm each; thus
such a group could not be used if the drawdown were to be
restricted to 30 feet. The graph could be used in a similar
manner for any given maximum drawdown. The drawdowns
are approximately directly proportional to the total discharged
Therefore, for greater or lesser rates of discharge, propor-
tionately lesser or greater maximum drawdowns lines should
be used. Thus, in the example above, if the discharge rate
had been 18,000 gpm and ihe maximum drawdown 30 feet,
the 15-foot drawdown line would have,.been used.

FLORIDA GEOLOGICAL SURVEY

SUMMARY AND CONCLUSIONS

The following progress has been made on the phases of
the investigation outlined in the introduction:

1. Data have been collected on more than 500 wells in
the well inventory.

2. Nine test wells have been constructed, four of which
penetrated the artesian aquifer to a depth of approximately
500 feet and five to a depth of 235 feet. Data concerning the
geologic and hydrologic characteristics of the artesian aqui-
fer were collected from these wells.

3. Chemical analyses have been made of water samples
from 18 wells. In addition, analyses for a few selected con-
stituents have been made of water samples from 23 wells.
Analyses for chloride have been made of more than 1,300
samples of ground water. Of these, approximately 550 were
made during the construction of the test wells to determine
the differences in the chloride content of the water from the
different zones of the artesian aquifer. Approximately 225
analyses for chloride were made of samples from wells that
are measured periodically to determine the relationship of
the chloride content of the water to the changes in water
levels. The remainder were made of water samples collected
during the well inventory.

4. Measurements of water levels are being made peri-
odically in 15 wells, and recording gages are being main-
tained on 7 wells to determine progressive trends and rapid
fluctuations which cannot be detected by periodic measure-
ments.

5. Rock cuttings have been collected from 21 wells in
the northeastern part of Volusia County to determine the
characteristics and extent of the geologic formations.

6. A pumping test was made to determine the trans-
missibility and storage coefficients of the upper part of the
artesian aquifer.

INFORMATION CIRCULAR NO. 8

As the investigation is incomplete at this time, final con-
clusions cannot be reached concerning all of the ground-
water problems confronting the county. However, from data
already collected, the following conclusions can be reached:

1. The northeastern part of Volusia County is underlain
by limestones of Eocene age. The oldest aquifer penetrated
by water wells in the county is the Avon Park limestone.
The top of the Avon Park limestone ranges in depth from
about 80 feet below the land surface in the central part of the
county to. about 200 feet along the east coast. The top of the
Ocala group, which overlies the Avon Park, is about 50 feet
below the land surface in the central part of the county and
about 100 feet at the coast. The Ocala group is the first
limestone penetrated by wells in most of the northeastern
part of Volusia County. Overlying the limestone of Eocene
age are 40 to 60 feet of shelly sand and clay beds of Miocene
or Pliocene age. Sands of Pleistocene and Recent age blanket
the deposits of Miocene or Pliocene age and form the land
surface.

2. Two sources of ground-water supplies in the area
covered by the investigation are the water-table aquifer and
the artesian aquifer.

The water-table aquifer is composed of sand beds of
Pleistocene and Recent age and sand or shell beds in the
sediments of late Miocene or Pliocene age. The water-table
aquifer is recharged locally by precipitation that falls on the
land surface and percolates downward. The water-table
aquifer usually supplies sufficient water for domestic use.

The artesian aquifer is comprised of limestone and dolo-
mites of Eocene age. Water is confined in the rocks of
Eocene age by clay beds in the deposits of Miocene or Plio-
cene age. The artesian aquifer is recharged principally in
the central part of the county and possibly to a lesser extent
elsewhere in the county wherever the water table stands at
a higher altitude than the artesian pressure head.

The permeable limestone and dolomite beds of the arte-
sian aquifer are separated by numerous thin beds of low

FLORIDA GEOLOGICAL SURVEY

permeability which retard the upward or downward move-
ment of water between the more permeable zones of the
aquifer. The artesian aquifer furnishes sufficient quantities
of water for municipal, agricultural, industrial, and com-
mercial needs in the northeastern part of Volusia County.

3. The chemical character of artesian water in the north-
eastern part of the county ranges considerably, depending on
the location and depth of the well sampled. Chemical analyses
show that the dissolved solids range from 136 ppm to 3,780
ppm; hardness, from 120 ppm to 1,060 ppm; and chloride
content, from 8 ppm to 1,860 ppm.

4. Records of water-level measurements indicate that
there has been no progressive areal decline in water levels
in recent years, although, locally, heavy pumping has caused
some decline.

5. Analysis of data collected during a pumping test indi-
cates that the upper part of the artesian aquifer west of
Daytona Beach has a transmissibility of 300,000 gpd/ft. and
storage coefficient of 0.0007. It indicates also that draw-
downs of 10 feet or so in the upper part of the aquifer do not
appreciably affect water levels in the lower part of the aqui-
fer in that area, presumably owing to the presence of layers
of low permeability which separate the different zones of the
aquifer. Probably drawdowns somewhat greater than 10 feet
also would not have a significant effect.

6. Salt-water contamination of artesian water supplies
in the coastal areas of Volusia County results from the up-
ward encroachment of saline water into the upper zones of
the aquifer. This occurs where fresh water in the aquifer
is underlain by salt water and heavy pumping lowers the
artesian pressure in the fresh-water portion sufficiently to
cause the salt water, whichthenhas a greater pressure head
than the fresh water, to move upward. Salt-water encroach-
ment c an be partially controlled in Volusia County by select-
ing areas where the upper part of the artesian aquifer is not
immediately underlain by salt water and by using proper
well spacing and pumping rates in well fields drawing heavily
from the upper zone of the artesian aquifer.

INFORMATION CIRCULAR NO. 8

The remaining phases of the investigation in Volusia
County will include:

1. An inventory of wells in the part of the county not
covered by this report.

2. Determination of the altitudes of measuring points on
wells so that water-level measurements may be referred
to sea level, and so that the direction of water movement and
areas of recharge and discharge may be mapped.

3. Collection of rock cuttings from wells in the remain-
ing parts of the county to complete the determination of the
character and extent of geologic formations.

4. Continuation of the periodic water-level measure-
ment program to establish long-range trends in water levels.

5. Preparation of a comprehensive report onthe ground-
water resources of the county.

FLORIDA GEOLOGICAL SURVEY

REFERENCES

Applin, E
1945

sther R.

(also see Applin, Paul L.)

(and Jordan, Louise) Diagnostic Foraminifera from
subsurface formations in Florida: Jour. Paleon-
tology, vol. 19, no. 2.

Applin, Paul L.
1944 (and Applin, Esther R.) Regional subsurface stra-
tigraphy and structure of Florida and southern
Georgia: Am. Assoc. Petroleum Geologists Bull.,
vol. 28, no. 12.

Barraclough, Jack T.

(see Heath, Ralph C., 1954).

Black, A. P.
1951 (and Brown, Eugene) Chemicalcharacter of Flor-
ida's waters 1951: Florida State Bd. of Cons.,
Water Survey and Research Paper 6.

Brown, Eugene

(see Black, A. P.)

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.
1945 Geology of Florida: Florida Geol. Survey Bull. 29.

Cooper, H. H., Jr.
1946 (and Jacob, C.E.) A generalized graphical method
of evaluating formation constants and summarizing
well-field history: Am. Geophys. Union Trans.,
1946, vol. 27.

Cooper, H. H., Jr.

(see Stringfield, V. T., 1951).

Heath, Ralph C.
1954 (and Barraclough, Jack T.) Interim report on the
ground-water resources of Seminole County, Flor-
ida: Florida Geol. Survey Information Circular
No. 5.

INFORMATION CIRCULAR NO. 8

Howard, C. S. (see Collins, W. D., 1928).

Jacob, C. E. (see Cooper, H. H., Jr.).

Jordan, Louise (see Applin, Esther R.).

MacNeil, F. Stearns
1947 Correlation chart of the outcropping Tertiary for-
mations of the eastern Gulf Region: U.S. Geol.
Survey, Oil and Gas Investigations Preliminary
Chart 29.

Neill, Robert M.
1955 Basic data of the 1946-47 study of ground-water
resources of Brevard County, Florida: U.S. Geol.
Survey open-file release.

Puri, Harbans S.
1953 Zonation of the Ocala group in Peninsular Florida
(abstract): Jour. Sedimentary Petrology, vol. 23.

Stringfield, V. T.
1936 Artesian water in the Florida peninsula: U. S.
Geol. Survey Water-Supply Paper 773-C.

Stringfield, V. T.
1951 (and Cooper, H. H., Jr.) Geologic and hydrologic
features of an artesian spring east of Florida:
Florida Geol. Survey Rept. of Investigations No. 7.

Vernon, R. O.
1951 Geology of Citrus and Levy counties, Florida:
Florida Geol. Survey Bull. .33.

Wenzel, L. K.
1942 Methods for determining permeability of water-
bearing materials, with special reference to dis-
charging-well methods: U.S. Geol. Survey Water-
Supply Paper 887.

FLRD GEOLOSk ( IC SUfRiW

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	Title Page
	Table of Contents
	Abstract
	Introduction
	Geography
	Geology
	Ground water
	Salt-water contamination
	Quantitative studies
	Summary and conclusions
	References