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 Title Page
 Florida State Board of Conserv...
 Transmittal letter
 Contents
 List of Illustrations
 Abstract
 Introduction
 Location and general features of...
 Test-well drilling
 Geologic formations and their water-bearing...
 Ground water
 Summary
 Well logs
 Bibliography


FGS FEOL



Water resource studies
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 Material Information
Title: Water resource studies ground water resources of the Naples area, Collier County, Florida ( FGS: Report of investigations 11 )
Series Title: ( FGS: Report of investigations 11 )
Physical Description: 64 p. : illus. ; 28 cm.
Language: English
Creator: Klein, Howard
Publisher: s.n.
Place of Publication: Tallahassee
Publication Date: 1954
 Subjects
Subjects / Keywords: Groundwater -- Florida   ( lcsh )
Water-supply -- Florida -- Collier County   ( lcsh )
Genre: non-fiction   ( marcgt )
 Notes
Funding: Report of investigations (Florida Geological Survey) ;
 Record Information
Source Institution: University of Florida
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The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: aleph - 000955565
oclc - 01723525
notis - AER8192
lccn - a 54009800
System ID: UF00001195:00001

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Table of Contents
    Title Page
        Page i
    Florida State Board of Conservation
        Page ii
    Transmittal letter
        Page iii
        Page iv
    Contents
        Page v
    List of Illustrations
        Page vi
        Page vii
    Abstract
        Page 1
        Page 2
    Introduction
        Page 2
        Page 3
        Page 4
    Location and general features of the area
        Page 5
        Page 4
        Page 6
        Page 7
    Test-well drilling
        Page 8
        Page 7
    Geologic formations and their water-bearing properties
        Page 8
        Page 9
        Page 10
        10a
        Page 11
        Page 12
        Page 13
    Ground water
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 13
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 52
    Summary
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
        Page 58
        Page 59
        Page 60
        Page 52
    Well logs
        Page 61
        Page 62
        Page 63
    Bibliography
        Page 64
        Page 63
        Copyright
            Copyright
Full Text


STATE OF FLORIDA
STATE BOARD OF CONSERVATION
Charlie Bevis, Supervisor

FLORIDA GEOLOGICAL SURVEY
Herman Gunter, Director



REPORT OF INVESTIGATIONS
No. 11


WATER RESOURCE STUDIES


GROUND-WATER RESOURCES
OF
THE NAPLES AREA, COLLIER COUNTY, FLORIDA


By
Howard Klein
Ground Water Branch
U.S. GEOLOGICAL SURVEY



Prepared By The
UNITED STATES GEOLOGICAL SURVEY
In cooperation with the
FLORIDA GEOLOGICAL SURVEY
and the
CITY OF NAPLES


TALLAHASSEE, FLORIDA
1954




- -. -1. `' B ;:: f
*r 1
wrv3/~I


FLORIDA STATE BOARD


OF

CONSERVATION


CHARLEY E. JOHNS
Acting Governor


R. A. GRAY
Secretary of State




J. EDWIN LARSON
Treasurer


NATHAN MAYO
Commissioner of Agriculture




THOMAS D. BAILEY
Superintendent Public Instruction


CLARENCE M. GAY
Comptroller


CHARLIE BEVIS
Supervisor of Conservation


CULTURAL
LtAlMV


RICHARD ERVIN
Attorney General








LETTER OF TRANSMITTAL













June 15, 1954


Mr. Charlie Bevis, Supervisor
Florida State Board of Conservation
Tallahassee, Florida

Dear Mr. Bevis:

Second only to sunshine in value, the State's water resources
are an important and necessary item in a progressive economy.
The Florida Geological Survey has been collecting water data
since its organization in 1907 and joined forces with the U. S.
Geological Survey in these studies beginning in 1930. This report
on the ground-water resources of the Naples area, Collier County,
Florida, prepared by Howard Klein, Geologist of the U. S.
Geological Survey, is a portion of the studies undertaken by the
two geological surveys.

'It is a pleasure to publish this report as Report of Investigations
No. 11, part of a continuing series of Water Resource Studies.

Respectfully,
Herman Gunter, Director











































Printed by ROSS PRINTING COMPANY, TALLAHASSEK, FLORIDA














CONTENTS


Abstract ........................

Introduction ....................
Purpose and scope ............
Acknowledgments.............

Location and general features of area
Geography and topography .......
Climate .....................

Test-well drilling ...... .........

Geologic formations and their water-bi
General conditions ...............
Miocene series ...................

Tampa formation .............
Hawthorn formation ..........

Tamiami formation ...........


Pleistocene and Recent series


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

hearing properties
................
................
................
. .. . . . .

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


Anastasia and Fort Thompson(?) formations

Pamlico sand and later deposits ..............

Ground water .................................
Principles of ground-water occurrence ...........
Hydrologic properties of aquifers ..............
Nonartesian aquifer ........ .............

Discharge ...............................
Recharge ............... .............
Shallow artesian aquifer ................
Discharge ..................... .........

Recharge .................. ............
Principal artesian aquifer .................

Water-level fluctuations .....................
Salt-water encroachment ......................
Contamination in nonartesian aquifer.....
Contamination in shallow artesian aquifer ....
Quality of water ............................
Quantitative studies ......... ..............
Ground-water use ............ ..............

Summary .............. ................
Well logs ............. .......................
Bibliography ....................................


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4





















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..











ILLUSTRATIONS


Figure Page
1. Map of Florida showing location of the Naples area in
Collier County .... .. ............................. 3
2. Naples area showing location of wells and location of
geologic sections ........ ..... ......................... 5
3. North-south geologic section, A-A', through the Naples
well field ....... ..... .. .... ........ Between 10 and 11
4. West-east geologic section, B-B', across Naples area ........... 11
5. Hydrograph of daily high and low water levels in well 107
showing the correlation of ground-water levels with
rainfall ................. ...... ...................... 20
6. Hydrograph of daily high and low water levels in well 88
showing the correlation of ground-water levels with
rainfall .............................. ............. 21
7. Contour map of water levels in the Naples area, February
12, 1952, showing the effect of concentrated pumping
in the golf course ........... ........................... 23
8. Contour map of water levels in the Naples area, March
12, 1952 ................... ............... ......... 24
9. Contour map of water levels in the Naples area, May
27, 1952 ................... ................ ... .... 25
10. Contour map showing the effect of well-field pumping on
water levels in the Naples area, February 11, 1952 ......... 27
lOa. Pumping and nonpumping water-level profiles along
North Fifth Avenue across the Naples peninsula, Feb-
ruary 11-12, 1952 ....... ....... .................... 29
11. Contour map showing the effect of well-field pumping on
water levels in the Naples area, May 26, 1952 ............. 31
12. Naples area showing maximum chloride concentration in
water from wells of various depths, analyzed during
course of investigation ................................. 41
13. Drawdown observed in wells 33 and 107 during pumping
test on Naples well field, August 7, 1952 .................. 45
14. Composite drawdown graph for wells 33 and 107 during
pumping test on Naples well field, August 7, 1952 ......... 46
15. Expected drawdowns at various distances from a well
pumping at a constant rate of 1,000 gpm after selected
time intervals ..................... ..... ... ........ 47

TABLES

Table Page
1, Average monthly temperature in degrees F, at Naples,
and a comparison of average monthly rainfall, in inches
at Naples and Bonita Springs ............................ 7
2. Chloride concentration in water samples from selected
w ell at N aples ............................................ 34
3. Analyses of water from selected wells at Naples ............... 38
4. Results of pumping tests on wells in the shallow artesian
aquifer at Naples ..... ....... .. ..... .... .... 43
5. Pumpage from Naples well field in millions of gallons per
m month ....... . ........ .... .. ............ 51
6. Water levels, in feet, referred to mean sea level ............... 55
7, Records of selected wells at Naples ........................... 58


vii









GROUNDWATER RESOURCES
OF THE NAPLES AREA, COLLIER COUNTY, FLORIDA
By
HowAnn KLEIN

ABSTRACT
Two shallow aquifers are the sources of fresh-water supplies in
the Naples area. The upper aquifer is under nonartesian conditions;
it extends from the land surface to a depth of 32 to 55 feet below
mean sea level. It is composed of the Pamlico sand and the Anastasia
formation of Pleistocene age and a portion of the upper part of the
Tamiami formation of late Miocene age. The upper aquifer is tapped
by several small, private irrigation wells and also by wells used to
supplement the municipal supply. The lower fresh-water aquifer is
under artesian pressure and is penetrated about 50 feet below mean
sea level in the city well field, where it extends to at least 80 feet
below mean sea level. The lower aquifer is much thicker north of
the city well field. It lies entirely within the Tamiami formation. It
supplies water to most of the city supply wells and to all the large
irrigation wells in the vicinity. The movement of water between
the aquifers is impeded by 5 to 20 feet of semi-impermeable marl
of the Tamiami formation.
Differences in the chemical quality of the water from the two
aquifers are slight. Samples of the water from the lower aquifer
in uncontaminated areas contain less than 250 parts per million (ppm)
of dissolved solids and also have a hardness less than 250 ppm. Water
from the upper aquifer usually contains slightly more' dissolved solids
than does that from the lower aquifer. Periodic chloride analyses
showed that some salt-water encroachment has occurred in both
aquifers in areas adjacent to the Gulf of Mexico and in the southern
part of the city.
Pumping tests indicate that the lower fresh-water aquifer has
a coefficient of transmissibility of about 92,000 gallons per day per
foot and a coefficient of storage of about 0.001. The maximum rate
of pumping from the aquifer is governed by the amount that ground-
water levels can be lowered before salt water moves into the area
of pumping. By applying data computed from pumping tests, it
was determined that the aquifer, as now developed by means of
the city wells and other wells of substantial yield, will not support





FLORIDA GEOLOGICAL SURVEY


heavy withdrawals for a period of more than 1 day during dry periods.
It is essential that wells of large yield which means, essentially,
those in the city well field be shut down daily to allow recovery
of water levels, if salt-water encroachment is to be averted. Addi-
tional ground-water supplies could be obtained from the thick, per-
meable parts of both fresh-water aquifers in the area north of the
present well field.


INTRODUCTION
PURPOSE AND SCOPE
Because of the rapid growth in both the seasonal and the permanent
population of Naples, Collier County, Fla., the residents and city
officials were faced with a problem of maintaining an adequate water
supply. They recognized the necessity for a ground-water survey
on the basis of which steps could be taken to protect the present
water supply, and to determine the most feasible means of increasing
water supplies to meet expanding demands. The city estimated that
its present water-plant facilities should provide for an anticipated
population of 12,000 to 15,000, or more than 30 million gallons of
water per month. The peak monthly output to date was 12.3 million
gallons, in March 1952.
In view of the ever-threatening possibility of salt-water encroach-
ment from the Gulf of Mexico into the well field, and the experience
of the previous salting of the old municipal well field in the southern
part of the city, the Naples City Council requested the United States
Geological Survey to investigate the ground-water resources of the
area, and to determine the ground-water potential of the aquifers
that might be used for the future development of water supplies
for municipal and other uses.
Field work started in August 1951 and was continued intermittently
through August 1952. A partial inventory of the existing wells was
made, elevations of measuring points for water-level measurements
were determined by spirit level, and a schedule of well-water sampling
for chloride analyses was set up.
The investigation was under the general supervision of A. N.
Sayre, Chief, Ground Water Branch, U. S. Geological Survey, and
Herman Gunter, Director, Florida Geological Survey; immediate
supervision was given by N. D. Hoy, District Geologist, U. S. Geolog-
ical Survey, Miami, Fla. The Florida Survey and the Federal Survey





FLORIDA GEOLOGICAL SURVEY


heavy withdrawals for a period of more than 1 day during dry periods.
It is essential that wells of large yield which means, essentially,
those in the city well field be shut down daily to allow recovery
of water levels, if salt-water encroachment is to be averted. Addi-
tional ground-water supplies could be obtained from the thick, per-
meable parts of both fresh-water aquifers in the area north of the
present well field.


INTRODUCTION
PURPOSE AND SCOPE
Because of the rapid growth in both the seasonal and the permanent
population of Naples, Collier County, Fla., the residents and city
officials were faced with a problem of maintaining an adequate water
supply. They recognized the necessity for a ground-water survey
on the basis of which steps could be taken to protect the present
water supply, and to determine the most feasible means of increasing
water supplies to meet expanding demands. The city estimated that
its present water-plant facilities should provide for an anticipated
population of 12,000 to 15,000, or more than 30 million gallons of
water per month. The peak monthly output to date was 12.3 million
gallons, in March 1952.
In view of the ever-threatening possibility of salt-water encroach-
ment from the Gulf of Mexico into the well field, and the experience
of the previous salting of the old municipal well field in the southern
part of the city, the Naples City Council requested the United States
Geological Survey to investigate the ground-water resources of the
area, and to determine the ground-water potential of the aquifers
that might be used for the future development of water supplies
for municipal and other uses.
Field work started in August 1951 and was continued intermittently
through August 1952. A partial inventory of the existing wells was
made, elevations of measuring points for water-level measurements
were determined by spirit level, and a schedule of well-water sampling
for chloride analyses was set up.
The investigation was under the general supervision of A. N.
Sayre, Chief, Ground Water Branch, U. S. Geological Survey, and
Herman Gunter, Director, Florida Geological Survey; immediate
supervision was given by N. D. Hoy, District Geologist, U. S. Geolog-
ical Survey, Miami, Fla. The Florida Survey and the Federal Survey






REPORT OF INVESTIGATIONS NO. 11


have been cooperating in general investigations of the geology and
ground water of the State since 1930.

Julia Gardner, paleontologist of the U. S. Geological Survey,
examined and identified fossil specimens and indicated tentative
geologic ages for them. Chemical analyses of water samples were
made by the Quality of Water Branch, U. S. Geological Survey.
The data of this report will be incorporated in a later report
covering the ground-water resources of Collier County (fig. 1). The
need for such a report is shown by the increased use of ground water
for agricultural and municipal purposes within the county.
The principal sources of published information pertinent to west-
ern Collier County are in the form of brief references incorporated





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EVEROLADES



0 2 4,0 0 80 10 MILES .*.


FIGURE 1. Map of Florida showing location of the Naples area in Collier
County.





FLORIDA GEOLOGICAL SURVEY


in Florida Geological Survey Bulletins 18 (Mansfield, 1939), 27
(Parker and Cooke, 1944), and 29 (Cooke, 1945), and in Water-
Supply Papers 319 (Matson and Sanford, 1913), 596-G (Collins and
Howard, 1928), and 773-C (Stringfield, 1936). In addition, some
quality-of-water data have been collected by the U. S. Geological
Survey during more recent years. No detailed ground-water studies
had been made in Collier County prior to the present investigation.

ACKNOWLEDGMENTS
The investigation was greatly aided by the cooperation of residents
and business establishments who supplied much valuable data and
permitted water sampling of wells. F. M. Lowdermilk, City Manager,
W. B. Uihlein, Chairman of the Naples Water Committee, and W. F.
Savidge, Water Plant Superintendent, gave valuable assistance during
the survey. J. P. Maharrey of Fort Myers and Chisholm Rivers of
Naples, well drillers, supplied data on water wells in the area. A. D.
Miller and Claude Storter of the Naples Co. granted permission for
drilling a test well on company property and permitted frequent water
sampling of wells at the Naples Golf Course. J. G. Sample and H. H.
McGee permitted the running of a pumping test using the irrigation
wells in J. G. Sample's citrus grove.

LOCATION AND GENERAL FEATURES OF THE AREA
GEOGRAPHY AND TOPOGRAPHY
The area covered by this report includes the city of Naples (fig. 1)
and adjacent parts of Collier County. The larger part of the city
of Naples, (fig. 2) is on a small peninsula which separates Naples
Bay and the Gordon River from the Gulf of Mexico. The remainder
of the city includes small areas east of the bay and the river. The
peninsula is more than 1% miles wide at the northernmost reaches
of the Gordon River and tapers southward to a point at Gordon Pass
where Naples Bay joins the Gulf of Mexico.
The surface elevation on the peninsula ranges from 15 to 25 feet
above sea level in the north and north-central portions and slopes
off gradually to the south and east and more abruptly at the Gulf
beach. The southern extremity of the peninsula and the areas border-
ing Naples Bay and the Gordon River are relatively flat with an
average elevation of about 5 feet. During severe storms and ex-
cessively high tides sea water moves into Naples Bay and the Gordon
River, flooding areas adjacent to the bay and portions of the southern












I"/


/
/
/


NI


EXPLANATION
*
WELL

CITY SUPPLY AND OTHER
WELLS OF LARGE YIELD
A
WELL EQUIPPED WITH
RECORDING GAGE
A A
LOCATION OF GEOLOGIC
SECTION


5 1114 Go o"t 1 o00"

PIGURE 2. Naples area showing location of Wells and location of geologic
;sections.


REPORT OF INVESTIGATIONS No. 11





FLORIDA GEOLOGICAL SURVEY


in Florida Geological Survey Bulletins 18 (Mansfield, 1939), 27
(Parker and Cooke, 1944), and 29 (Cooke, 1945), and in Water-
Supply Papers 319 (Matson and Sanford, 1913), 596-G (Collins and
Howard, 1928), and 773-C (Stringfield, 1936). In addition, some
quality-of-water data have been collected by the U. S. Geological
Survey during more recent years. No detailed ground-water studies
had been made in Collier County prior to the present investigation.

ACKNOWLEDGMENTS
The investigation was greatly aided by the cooperation of residents
and business establishments who supplied much valuable data and
permitted water sampling of wells. F. M. Lowdermilk, City Manager,
W. B. Uihlein, Chairman of the Naples Water Committee, and W. F.
Savidge, Water Plant Superintendent, gave valuable assistance during
the survey. J. P. Maharrey of Fort Myers and Chisholm Rivers of
Naples, well drillers, supplied data on water wells in the area. A. D.
Miller and Claude Storter of the Naples Co. granted permission for
drilling a test well on company property and permitted frequent water
sampling of wells at the Naples Golf Course. J. G. Sample and H. H.
McGee permitted the running of a pumping test using the irrigation
wells in J. G. Sample's citrus grove.

LOCATION AND GENERAL FEATURES OF THE AREA
GEOGRAPHY AND TOPOGRAPHY
The area covered by this report includes the city of Naples (fig. 1)
and adjacent parts of Collier County. The larger part of the city
of Naples, (fig. 2) is on a small peninsula which separates Naples
Bay and the Gordon River from the Gulf of Mexico. The remainder
of the city includes small areas east of the bay and the river. The
peninsula is more than 1% miles wide at the northernmost reaches
of the Gordon River and tapers southward to a point at Gordon Pass
where Naples Bay joins the Gulf of Mexico.
The surface elevation on the peninsula ranges from 15 to 25 feet
above sea level in the north and north-central portions and slopes
off gradually to the south and east and more abruptly at the Gulf
beach. The southern extremity of the peninsula and the areas border-
ing Naples Bay and the Gordon River are relatively flat with an
average elevation of about 5 feet. During severe storms and ex-
cessively high tides sea water moves into Naples Bay and the Gordon
River, flooding areas adjacent to the bay and portions of the southern






FLORIDA GEOLOGICAL SURVEY


part of the peninsula. The Gulf side is protected by a beach ridge
which extends along the coast.
The peninsula is entirely blanketed by a permeable terrace sand,
the surface of which has been altered by winds and by washing of
heavy rains. The drainage of the area is chiefly underground because
rainfall rapidly percolates into the sandy mantle. Places of low
elevation are locally covered by a thin layer of sand mixed with
muck that is being formed by the decay of vegetation. The area is
marked by small natural and artificial lakes or ponds which receive
some overland runoff, as do the Gulf of Mexico and Naples Bay,
during short periods of heavy rainfall. The land just east of the
beach ridge in the northern part of the city is swampy and remains
inundated throughout much of the year.
The lower part of the peninsula is dissected to some extent by
drainage ditches and dredged-out boat basins. They are avenues of
possible extended salt-water encroachment.

CLIMATE
The climate at Naples is subtropical and the humidity is usually
high. The average annual temperature as shown by discontinuous
records of the U. S. Weather Bureau is 75.80 F., and the warmest
weather occurs during July and August. Table .1 shows monthly
and yearly averages of temperatures and rainfall at the Naples station
and rainfall at the Bonita Springs station, about 15 miles north of
Naples.
The average annual rainfall at Naples and Bonita Springs, from
discontinuous U. S. Weather Bureau records, is 52.19 inches and
54.30 inches, respectively. The heaviest rains occur during the
period June-October, inclusive. The greatest yearly rainfall on record
at Naples was 71.47 inches in 1947. During June of that year a total
of 17.79 inches of rain was recorded. However, the rainfall through-
out 1947, even during ordinarily dry months, was unusually high. The
year of lowest rainfall on record was 1944 with 30.93 inches.
Rainfall in this portion of the Gulf coast is not evenly distributed
really but is localized, as shown by table 1. Although the stations
are relatively close, appreciable variations are noted in monthly totals,
especially during months of heavy rainfall.







REPORT OF INVESTIGATIONS NO. 11


TABLE 1
Average monthly temperature, in degrees F, at Naples, and a
comparison of average monthly rainfall, in inches, at
Naples and Bonita Springs
Month Temperature1 Rainfall2
Naples Naples Bonita Springs
Jan ......................................... 67.2 1.15 1.20
Feb ........................................... 67.6 0.82 0.83
Mar .................................... 70.6 1.38 1.21
April ........................ ................ 75.9 2.57 1.84
M ay ......................................... 77.5 3.41 3.55
June ........................................ 82.0 8.88 8.78
July .............................. ........... 83.3 7.88 11.04
Aug ........................................... 84.0 7.71 10.00
Sept ...................................... 82.8 9.67 9.42
Oct ......................................... 77.9 5.56 4.02
Nov ........................................... 72.5 2.10 1.34
Dec ........................................... 68.6 1.06 1.07
Yearly average ..................... 75.8 52.19 54.30
1 Discontinuous record 1942-50, U. S. Weather Bureau.
2 Discontinuous record 1943-50, U. 8. Weather Bureau.

TEST-WELL DRILLING

Five 2-inch test wells, drilled under contract at Naples early in
1952, furnished information on the general subsurface geology of
the area. In addition, they were and will continue to be used to
gather data on ground-water-level fluctuation and for determining
the extent of salt-water encroachment from Naples Bay and the Gulf
of Mexico.
Three of the test wells, nos. 116, 117, and 118 (fig. 2), were drilled
to depths comparable to those of the city supply wells. Well 116,
drilled to 62 feet below mean sea level, is at the southwest corner
of South Golf Drive and Third Street, about 1,300 feet inland from
the Gulf of Mexico. Well 117, drilled to 72 feet below mean sea level,
is on Fifth Avenue North, east of the Tamiami Trail and approxi-
mately 1,500 feet west of the Gordon River. Well 118, just west of
the water plant, was drilled to 64 feet below mean sea 'level. With
such a distribution of test wells the municipal well field is encircled
by observation wells so that, by means of periodic sampling, any
extension of present salt-water encroachment may be detected. None
of the above tests showed any indication of salt-water encroachment.
Wells 119 and 123 were drilled to determine the depth at which
salt water occurs. Well 119, in the approximate center of the well
field, was drilled to 105 feet below mean sea level, at which depth a
pronounced increase in chloride was detected. Well 123, drilled to
145 feet below mean sea level, 0.7 mile north of the Naples Golf






FLORIDA GEOLOGICAL SURVEY


Course in an area only slightly effected by pumping, showed no
evidence of salt water. These wells similarly will serve as water-
level and chloride-sampling observation wells.
During the course of test drilling, specimens of the penetrated
material were collected, usually at 5-foot intervals, and examined.
Each time a permeable rock layer was penetrated the well was
pumped, and water samples were collected for chemical analyses
including chloride. Water samples from materials of low permeability
were collected with the bailer and were analyzed for chloride content
only.

GEOLOGIC FORMATIONS AND THEIR
WATER-BEARING PROPERTIES
GENERAL CONDITIONS
The strata underlying the Naples area to a depth of about 600
feet range in age from Miocene to Recent; however, strata of Pliocene
age apparently are missing. Deeper rocks older than Miocene contain
water of poor quality and are not discussed in this report.
MIOCENE SERIES
Formations of Miocene age are the oldest strata penetrated by
water wells in the Naples area. The Miocene series in the area
includes the Tampa formation, Hawthorn formation, and Tamiami
formation of early, middle, and late Miocene age, respectively.
TAMPA FORMATION1
The Tampa formation, as defined by Cooke (1945, pp. 111-113),
overlies the Suwannee limestone of Oligocene age and is gradational
with the overlying Hawthorn formation.
sandy limestone and calcareous sandstone are the chief components
of the Tampa formation. The sand, predominantly quartz, may
occur either disseminated in the matrix of the limestone or in thin
beds or pockets. The Tampa formation forms a part of the principal
artesian aquifer which underlies much of Florida and southeastern
Georgia (Stringfield, 1936, pp. 122-128) and for which Parker (1951,
p. 819) proposed the name Floridan aquifer. The Tampa formation
is permeable and is one of the major sources of irrigation water in
counties bordering the Gulf coast north of Collier County. The top
of the Tampa formation occurs between 600 and 640 feet below sea
level at Fort Myers and the formation ranges from 80 to 120 feet
1The geologic nomenclature used in this report conforms to the nomenclature of the Florida
Geological Survey. It conforms also to that of the U. 8. Geological Survey with the ex-
ception that the Tampa formation is used instead of Tampa limestone.







REPORT OF INVESTIGATIONS NO. 11


TABLE 1
Average monthly temperature, in degrees F, at Naples, and a
comparison of average monthly rainfall, in inches, at
Naples and Bonita Springs
Month Temperature1 Rainfall2
Naples Naples Bonita Springs
Jan ......................................... 67.2 1.15 1.20
Feb ........................................... 67.6 0.82 0.83
Mar .................................... 70.6 1.38 1.21
April ........................ ................ 75.9 2.57 1.84
M ay ......................................... 77.5 3.41 3.55
June ........................................ 82.0 8.88 8.78
July .............................. ........... 83.3 7.88 11.04
Aug ........................................... 84.0 7.71 10.00
Sept ...................................... 82.8 9.67 9.42
Oct ......................................... 77.9 5.56 4.02
Nov ........................................... 72.5 2.10 1.34
Dec ........................................... 68.6 1.06 1.07
Yearly average ..................... 75.8 52.19 54.30
1 Discontinuous record 1942-50, U. S. Weather Bureau.
2 Discontinuous record 1943-50, U. 8. Weather Bureau.

TEST-WELL DRILLING

Five 2-inch test wells, drilled under contract at Naples early in
1952, furnished information on the general subsurface geology of
the area. In addition, they were and will continue to be used to
gather data on ground-water-level fluctuation and for determining
the extent of salt-water encroachment from Naples Bay and the Gulf
of Mexico.
Three of the test wells, nos. 116, 117, and 118 (fig. 2), were drilled
to depths comparable to those of the city supply wells. Well 116,
drilled to 62 feet below mean sea level, is at the southwest corner
of South Golf Drive and Third Street, about 1,300 feet inland from
the Gulf of Mexico. Well 117, drilled to 72 feet below mean sea level,
is on Fifth Avenue North, east of the Tamiami Trail and approxi-
mately 1,500 feet west of the Gordon River. Well 118, just west of
the water plant, was drilled to 64 feet below mean sea 'level. With
such a distribution of test wells the municipal well field is encircled
by observation wells so that, by means of periodic sampling, any
extension of present salt-water encroachment may be detected. None
of the above tests showed any indication of salt-water encroachment.
Wells 119 and 123 were drilled to determine the depth at which
salt water occurs. Well 119, in the approximate center of the well
field, was drilled to 105 feet below mean sea level, at which depth a
pronounced increase in chloride was detected. Well 123, drilled to
145 feet below mean sea level, 0.7 mile north of the Naples Golf






FLORIDA GEOLOGICAL SURVEY


Course in an area only slightly effected by pumping, showed no
evidence of salt water. These wells similarly will serve as water-
level and chloride-sampling observation wells.
During the course of test drilling, specimens of the penetrated
material were collected, usually at 5-foot intervals, and examined.
Each time a permeable rock layer was penetrated the well was
pumped, and water samples were collected for chemical analyses
including chloride. Water samples from materials of low permeability
were collected with the bailer and were analyzed for chloride content
only.

GEOLOGIC FORMATIONS AND THEIR
WATER-BEARING PROPERTIES
GENERAL CONDITIONS
The strata underlying the Naples area to a depth of about 600
feet range in age from Miocene to Recent; however, strata of Pliocene
age apparently are missing. Deeper rocks older than Miocene contain
water of poor quality and are not discussed in this report.
MIOCENE SERIES
Formations of Miocene age are the oldest strata penetrated by
water wells in the Naples area. The Miocene series in the area
includes the Tampa formation, Hawthorn formation, and Tamiami
formation of early, middle, and late Miocene age, respectively.
TAMPA FORMATION1
The Tampa formation, as defined by Cooke (1945, pp. 111-113),
overlies the Suwannee limestone of Oligocene age and is gradational
with the overlying Hawthorn formation.
sandy limestone and calcareous sandstone are the chief components
of the Tampa formation. The sand, predominantly quartz, may
occur either disseminated in the matrix of the limestone or in thin
beds or pockets. The Tampa formation forms a part of the principal
artesian aquifer which underlies much of Florida and southeastern
Georgia (Stringfield, 1936, pp. 122-128) and for which Parker (1951,
p. 819) proposed the name Floridan aquifer. The Tampa formation
is permeable and is one of the major sources of irrigation water in
counties bordering the Gulf coast north of Collier County. The top
of the Tampa formation occurs between 600 and 640 feet below sea
level at Fort Myers and the formation ranges from 80 to 120 feet
1The geologic nomenclature used in this report conforms to the nomenclature of the Florida
Geological Survey. It conforms also to that of the U. 8. Geological Survey with the ex-
ception that the Tampa formation is used instead of Tampa limestone.






REPORT OF INVESTIGATIONS NO. 11


in thickness (Hoy and Schroeder, 1952). It is possible that well
115 (fig. 2), drilled to a depth of 540 feet, penetrates the Tampa
formation. The formation yields only salty water in this and adjacent
areas.
HAWTHORN FORMATION
Rocks younger than the Tampa and older than late Miocene in
age are referred to the Hawthorn formation by Cooke (1945, p. 144)
and Vernon (1951, pp. 186-187).
The Hawthorn formation is composed chiefly of gray-green clay,
silt, and fine sand and interbedded limestone and shell marl. Perme-
able limestone and shell beds in the lower part of the formation are
regarded as the uppermost part of the principal artesian aquifer
(Stringfield, 1936, p. 130), and are the probable sources of the deep,
freely flowing artesian wells at Naples. The overlying clay and silt
sections, however, are relatively impermeable and separate the water
of the principal artesian aquifer from the shallow artesian beds, such
as the shallow confined aquifer of the Naples area. At Fort Myers
the top of the Hawthorn formation occurs at depths between 40 and
55 feet below the land surface. At Goodland, south of Naples, the
top of the Hawthorn formation lies between 150 feet and 270 feet
below the land surface. By projection, the clay and silt of the
Hawthorn should be encountered at a depth of about 170 feet in the
Naples area. The formation is about 400 feet thick in this area.
None of the test wells at Naples were deep enough (maximum depth
157 feet) to penetrate material which appeared to be of Hawthorn
age.
TAMIAMI FORMATION
All materials of late Miocene age in southern Florida are assigned
to the Tamiami formation by Parker (1951, p. 823); thus the upper
part of the Hawthorn formation of Parker and Cooke (1944, pp. 98-
112), the Tamiami formation, and Mansfield's (1939, p. 8) Buckingham
limestone and Tamiami limestone are incorporated as a unit the
Tamiami formation.
The macrofossil content of test-well samples has been studied
from depths ranging from 20 feet to 70 feet. Julia Gardner states:
"No species have been determined from the Tamiami fauna, but
the general character of the assemblage is uniform: Pecten, Anomia,
Ostrea, and Balanus, all of them fragmented, possibly from the surf
on the old Tamiami reef." The samples contained Glycymeris sp. and
Turritella sp. of a pattern common to the upper Miocene of Florida.
The Tamiami formation is composed primarily of light-tan and





FLORIDA GEOLOGICAL SURVEY


gray fossiliferous sandy limestone and interbedded gray-green sandy
and shelly marl. Although not precisely located, the top of the
formation at Naples generally occurs between 15 feet and 30 feet
below mean sea level. The Tamiami formation may be more than
125 feet thick at Naples.
The upper part of the Tamiami formation is composed predom-
inantly of beds or lenses of soft, relatively impermeable greenish-
gray marl and minor beds of gray permeable limestone. The marly
sediments generally are poorly sorted and act as a semi-impervious
barrier or confining bed which retards the vertical movement of
ground water. This relatively impermeable zone ranges in thickness
from 5 feet to 20 feet and is apparently thickest in the Naples well-
field area.
Data from drillers' logs and from recent test drilling indicate
that the first thick permeable limestone that underlies the confining
bed is the most persistent fresh-water-bearing rock in the Naples
area. This limestone is the main aquifer and is sufficiently thick
that a well penetrating it will have at least 5 to 10 feet of open-hole
finish. The upper surface of this permeable rock occurs at approxi-
mately 50 feet below mean sea level at the municipal well-field area
and apparently slopes very gently toward the Gulf.
Wells 119 and 123 are of sufficient depth to furnish more complete
information concerning the hydrologic properties of deeper parts
of the Tamiami formation. The greatest permeability in well 119
was at the intervals between 50 to 61 feet and 70 to 74 feet below
mean sea level. Below 74 feet unconsolidated material, which occurs
as thin beds of calcareous sand or cavity fillings in the limestone, and
dense limestone beds reduce the permeability. If well 119 can be
used as an index of the general conditions at the well field, a depth
of 80 to 85 feet below mean sea level is the maximum to which supply
wells in that vicinity may be drilled. Not only is there a decrease
in permeability with greater depth, but there is also an increase in
salinity of the ground water.

North of the well field, as data from well 123 show, the lower
part of the Tamiami formation to a depth of 145 feet below sea level
is composed of limestone of varying degrees of cementation. This
thick rock zone is a possible source of large quantities of fresh water.
The limestone is riddled with solution cavities which are usually
filled with loose sand. When penetrated by drilling, the loose material
slumps or caves, but can be bailed or pumped clear. j











FLORIDA GEOLOGICAL SURVEY


Report of Investigations No. 11


NONARTESIAN


SHALLOW


TESI
ARTESIAN


30



40



50



60



7o



-80



-90



100



110



120



130



140


A QUIFER


AQUIFER


SCALE IN FEET
500 0 500. 1,000


FIGURE 3. North-south geologic section, A-A', through the


Naples well field.


Vi^.


10











20


EXPLANATION

l SAND
E MARL
SSHELLS, MARINE
LIMESTONE
A
123
/)I

116/ CROSS SECTION A-A'
o SHOWING PROJECTION OF
\ WELL 116 ONTO NORTH-
\ SOUTH LINE. SEE FIG, 2
119i FOR LOCATIONS.



118
A


_ I





REPORT OF INVESTIGATIONS No. 11


Rapid changes in lithology are noted in a horizontal direction as
well as vertically. These variations may be either gradational or
fairly abrupt. A thickness of limestone or shelly marl at a certain
depth in one test well may be no indication that a corresponding
bed will be present at a comparable depth in another well. However,
the thicker permeable limestone layers are fairly consistent throughout
the area and may be tentatively correlated from one well to another
(figs. 3 and 4).
PLEISTOCENE AND RECENT SERIES
Deposits of Pliocene age are not known to occur in the Naples
area. In describing the faunal assemblage from a sample taken at


FIGURE 4. West-east geologic section B-B', across Naples area.


11






FLORIDA GEOLOGICAL SURVEY


28 feet from test well 119 Julia Gardner states: "None of the species
listed would be out of place in either a Pliocene or a Pleistocene fauna.
However, the assemblage is unlike any I have seen from the Pliocene.
Very few of the dominant species of the Caloosahatchee (Pliocene)
are present." The assemblage collected at 28 feet from well 119 in-
cludes:
Anadara sp.; juvenile. Group of A. transversa (Say) but rela-
tively wider.
Carditamera floridana Conrad? juvenile
Bellucina aminata Dall
Cardium sp.
Chione (Chione) cancellata (Linnaeus)
Chione (Timoclea) qrus (Holmes)
Ervilia? sp. juvenile
Corbula (Caryocorbula) barrattiana C. B. Adams
Diodora alternate (Say)
Turritella tips
Young Columbellids?
Nassarius vibex (Say)
Olivella sp. cf. 0. mutica (Say)
Turrids juvenile
In the absence of contrary information, the deposits containing
the fauna listed are included in the Pleistocene series in this report.
Rocks of known Pleistocene age in Naples and vicinity are the
Anastasia formation, the Fort Thompson formation or an equivalent,
and the Pamlico sand. The Recent series is represented by black
mucky sands.
ANASTASIA AND FORT THOMPSON (?) FORMATIONS
The Anastasia formation represents materials deposited during
part of Pleistocene time. In the Naples area it is composed of light-
cream to light-gray sandy limestone and gray to tan shelly, sandy
marl containing an abundance of Chione cancellata. The limestone
of the Anastasia formation thickens eastward where its top occurs
at higher elevations than at the center of the Naples area. It seems
apparent that the Anastasia formation originally covered the Naples
area, but was subjected to beach erosion and was partially removed
prior to the deposition of the surface sand.
A thin bed of shelly marl overlies the limestone beds of the
Anastasia in many places. In places the marl contains small fragile
shells of gastropods (snails) of fresh-water origin. It may represent


12






REPORT OF INVESTIGATIONS NO. 11


or be equivalent to part of the Fort Thompson formation, which was
deposited during one of the glacial stages of the Pleistocene.
The Anastasia formation exhibits a lack of uniformity in deposi-
tion similar to that of the Tamiami formation. The only correlatable
unit is a hard fossiliferous tan to gray limestone which is the shal-
lowest water-bearing limestone in the Naples area. According to
information received from well drillers, this limestone bed of the
Anastasia formation is often encountered within 10 feet of the surface
in adjacent areas east of the Gordon River and causes very difficult
drilling. In test well 117 this stratum occurs 20 feet below the surface
and is about 15 feet thick. The same hard limestone was noted in
well 123 between 36 and 44 feet below the surface. It is reported
that this water-producing rock was penetrated at about 28 feet in
well 110, but the precise thickness there is not known. In the western
and southern parts of the peninsula the rock is very thin or missing
as a result of erosion during pre-Pamlico time.
PAMLICO SAND AND LATER DEPOSITS
The Naples area is entirely blanketed by the terrace deposits of
the Pamlico sand which in places is mixed with Recent black mucky
sands. The altitude of the terrace is everywhere less than 25 feet.
The Pamlico sand is composed of fine to medium sand, the base of
which lies at a depth of 10 to 15 feet below mean sea level. The
uppermost material is white or light gray medium-grained quartz
.sand which grades downward to highly colored rust-brown fine-
grained quartz sand. The color is apparently the result of the vertical
migration of organic materials in percolating ground water. The
components of the Pamlico sand are sufficiently well sorted to permit
the ready intake of rainfall and to allow easy downward percolation.
The Pamlico sand will supply small quantities of water to shallow
sand-point wells.

GROUND WATER
PRINCIPLES OF GROUND-WATER OCCURRENCE
Ground water is stored in .the openings, solution cavities, and
pore spaces within the consolidated and unconsolidated materials of
the earth's crust. The openings or voids between particles vary in
size because of the nonhomogeneous character of the sediments. The
frequency and the size of the openings determine the porosity, which
is expressed as the ratio of the volume of the interstices to the volume
of rock mass (Meinzer, 1923, p. 19). Clay is one of the most porous


13






FLORIDA GEOLOGICAL SURVEY


of all natural earth materials, but is also one of the least permeable.
Permeability in water-bearing materials is the property of trans-
mitting water under a gradient.
Well sorted, unconsolidated sands or silts, regardless of the size
of the components, are highly porous but the permeability varies
with the size of the pores. Admixtures of particles of various sizes
such as sandy clay, marly sand, or shelly marl may be of low porosity
and are of low permeability because the smaller grains occupy the
voids between large grains. In consolidated rocks, porosity and
permeability may be reduced by the filling of openings with cementing
material.
Clay, marl, or fine sand, although highly porous, are capable of
transmitting only small quantities of ground water. Coarse sand or
gravel and cavernous limestone, however, transmit ground water with
great facility. The consolidated rock layers underlying Naples are
highly permeable because the network of interconnected solution
cavities permit the ready movement of water. Any natural geologic
formation that transmits water in sufficient quantities to supply a well
is called an aquifer.
All the water that supplies the wells in the Naples area is derived
from local rainfall. Not all of the rainfall, however, percolates through
the surface sand to the water table, the remainder being lost by
evaporation and transpiration or by overland runoff into the Gordon
River, Naples Bay, and the Gulf of Mexico. The water table is the
surface below which earth materials are completely saturated.
Ground water that is, water below the water table moves
laterally under gravitational influence from points of recharge to
points of artificial discharge such as wells, and to places of natural
discharge such as springs, lakes or streams. It is this natural ground-
water discharge that largely maintains streamflow and lake levels
during dry periods.
The water table is an undulating surface conforming in a general
way to the topography of the land, being higher under hills than under
valleys. It fluctuates seasonally, rising during seasons of heavy rain
and falling during periods of low rainfall. It fluctuates also in response
to many other forces such as evaporation, transpiration, and pumping
from wells.

An aquifer that is not overlain by impermeable material contains
water under nonartesian or unconfined conditions. The water in a


14






REPORT OF INVESTIGATIONS No. 11


well penetrating an unconfined aquifer will not rise above the point
where the water was encountered in drilling the well. The shallow
aquifer at the Naples well field is a nonartesian aquifer because
the overlying materials are permeable. The aquifer is tapped by
many wells, such as well 110, and the water level in each well is a
measure of the altitude of the water table in that immediate area.
Where ground water has moved laterally into permeable material
that is overlain by a relatively impervious cover, it is said to occur
under artesian (confined) conditions. The water level in a well pene-
trating an artesian aquifer will rise above the top of the aquifer to
a point that is the approximate measurement of the pressure head.
The pressure head is due to the weight of the water at higher eleva-
tions in the aquifer. The water level of an artesian aquifer is known
as the piezometric surface, and wherever it is above the land surface,
wells tapping the aquifer will flow. The piezometric surface of an
artesian aquifer fluctuates in response to the same forces that affect
the water table, and also in response to forces like earthquakes, pass-
ing trains, and hurricanes and other storms, that generally do not
affect the water table directly (Parker and Stringfield, 1950).

HYDROLOGIC PROPERTIES OF THE AQUIFERS
Ground-water supplies in the Naples area occur in three separate
aquifers having different water levels and water quality. These are
designated as: (1) nonartesian aquifer containing water under water-
table or unconfined conditions; (2) shallow aquifer containing water
under artesian conditions; and, (3) principal artesian aquifer (Flor-
idan aquifer) containing saline water under artesian conditions.
NONARTESIAN AQUIFER
The nonartesian aquifer in the Naples area is usually composed
of the Pamlico sand, the Anastasia formation, and that part of the
Tamiami formation which overlies the main confining marl. The
permeability of the aquifer is highest in the vicinity of wells 110,
116, 117, and 123, as in these areas the section between the surface
sand and the confining bed is composed almost entirely of cavernous
limestone which remains open after penetration. In these areas lime-
stone of the Anastasia formation is immediately underlain by con-
solidated parts of the upper part of the Tamiami formation. Regard-
less of the difference in geologic age of the rocks the entire section
is a single, connected, unconfined, hydrologic unit. In other areas
such as at wells 118 and 119 and over much of the northern part of
the well field the nonartesian aquifer is least productive because


15






FLRIDA GEOLOGICAL SURVEY


limestone beds are very thin or missing and the aquifer consists mainly
of sand and marl.
The base of the nonartesian aquifer is an undulating surface
ranging in depth from about 32 feet below mean sea level in the
south to 55 feet in the north. The aquifer is the source of water for
several small privately owned irrigation wells and for public-supply
well 110.
Discharge
Ground-water losses from the nonartesian aquifer occur naturally
by seepage and evapotranspiration, and by pumping from wells. Con-
siderable discharge undoubtedly occurs through submarine seeps
where the aquifer crops out beneath the Gulf and Naples Bay. Losses
through seepage are greatest during periods of high rainfall when
ground-water levels are highest. Another part of the seepage loss
occurs where nonartesian water percolates downward through the
less permeable confining bed to the lower fresh-water aquifer. Also
of major importance is the quantity of water lost through evaporation
and transpiration. Ground-water losses due to evaporation and tran-
spiration are greatest when the water table is high and decrease as
the water table declines. Losses resulting from these natural processes
greatly exceed the quantity of water withdrawn from the aquifer
by pumping from wells.
When water is pumped from a well penetrating the nonartesian
aquifer, the dewatering of the material causes a rapid lowering of the
water table in the immediate vicinity of the well, thus establishing a
hydraulic gradient toward the well. The water table assumes the
form of an inverted cone centered at the discharge point. As pumping
continues at a constant rate, the water table at the well declines pro-
gressively but at a slowly decreasing rate, until a point of near-equi-
librium is reached in the vicinity of the well whereby the rate of
discharge is balanced by an equal amount of water being transmitted
to the center of withdrawal. At the same time, the cone of depression
or cone of influence (Meinzer 1923, p. 61) spreads so that the water
table is lowered at greater distances from the well; thus, water from
more distant parts of the aquifer is being diverted to the pumped area.
As pumping proceeds, the water table continues its slow decline and
the cone of depression spreads farther unless recharge is made avail-
able to the aquifer. If recharge is sufficient to balance withdrawals,
the spreading of the cone progresses no farther, and the water level
at the pumped well remains essentially constant. An additional deep-
ening and spreading of the cone would result if the pumping rate






REPORT OF INVESTIGATIONS NO. 11


were to increase or if another nearby well in the aquifer started
pumping. When pumping from the well ceases, the water level im-
mediately starts to recover, rapidly at first, then at a slowly decreasing
rate to a point of essentially the original nonpumping level. The
rate at which drawdown and recovery proceed in the vicinity of a
well depends in part upon the permeability of the aquifer. Pumping
from material of high permeability produces a small drawdown with
a wide shallow cone of depression; in material of low permeability a
narrow deep cone develops.
Because the peninsula is bounded on the west, south, and east by
bodies of salt water, these must be considered as the boundaries of
the shallow aquifer, for an excessive lowering of the water table in
these extreme areas would result in drawing in salt water laterally.
To the north, however, the aquifer is of much greater areal extent.
Recharge
The main recharge to the nonartesian aquifer is that part of the
total rainfall that percolates downward to the zone of saturation. A
general rise in the water table at Naples occurs when rain falls in
the immediate vicinity of the city. Rainfall to the north and east
may or may not effect the water table in the city itself. The relatively
flat topography and the permeable sandy cover throughout the area
permit little surface runoff and the largest drainage is underground.
It is possible that during high water stages some water is recharged
to the aquifer from the Gordon River. This seepage would occur only
for a short interval because as the stream level is lowered the water
would drain back into the stream and the normal streamward gradient
of the water table would be restored.
When the effect of pumping nonartesian wells (lowering of the
water table) reaches an area where natural surface-water or ground-
water discharge occurs into the Gulf of Mexico, Naples Bay, or Gordon
River, some of the water normally lost through this discharge would
be diverted toward the pumped area; thus rejected recharge and
normally wasted water would be salvaged. The water levels in the
shallow lakes at Naples and in the swampy area to the north denote
the height of the water table in those areas. If the spreading of the
cone of influence were to include any of these lakes, the water level
in that lake would lower slowly owing to the fact that its water was
being moved toward the pumping area. The diversion of normally
rejected water retards the spreading of the cone of depression.
During dry periods some recharge occurs through the seepage of


17






FLORIDA GEOLOGICAL' SURVEY


irrigation water to the water table. The amount thus supplied is
small because evaporation and transpiration rates increase during
dry times.
SHALLOW ARTESIAN AQUIFER
The top of the shallow artesian aquifer at Naples occurs between
40 and 70 feet below mean sea level. Exclusive of well 110 it is the
source of water for all city supply wells and also the source for several
privately owned irrigation wells including the large-diameter wells
at the golf course (wells 78, 79, 80, 136, fig. 2), and J. G. Sample's
citrus grove (wells 71, 72, 73, 74, 98, fig. 2). Well 110 whose bottom
is 32 feet below mean sea level, and the lower 12 feet of which is
uncased shows no evidence of hydraulic connection between the
nonartesian and shallow artesian aquifers; the water level in the
well shows no fluctuation when the pumps are being turned on and
off in the remainder of the field. From this fact and from test-drilling
data it is certain that in the well field the nonartesian and shallow
artesian aquifers are separated by a confining bed or beds.
Different conditions appear to exist south of the well field and in
areas of the eastern part of the peninsula. Test well 118 penetrated
a series of beds or lenses of slightly permeable sandy marl and thin
layers of permeable limestone beneath the nonartesian aquifer. It is
possible that some interconnection exists between the two fresh-water
aquifers, so that south of the well field their entire thickness may
be a single hydrologic unit. In support of this speculation is the
fact that each time a highly permeable zone was encountered during
drilling well 118, the water level in the well remained at the level
of the water table. This cannot be considered conclusive evidence,
however, because the land-surface and water-table elevations are
lower in the south and the water-table elevation approaches the eleva-
tion of the water surface in the shallow artesian aquifer. East of
the well field also, the confining layer becomes thinner and thus may
permit increased movement of water between aquifers. In well 117
the water table was 0.5 foot higher than the piezometric surface and
in wells 116 and 123 the water table ranged from 2 to 3 feet higher
than the piezometric surface of the shallow artesian aquifer.
Material overlying an artesian aquifer may either effectively con-
fine or partially confine the water in the aquifer. Effective confine-
ment is produced by impermeable beds, but slightly permeable con-
fining beds retard rather than prevent percolation of water (Meinzer,
1923, p. 40). Probably the confining material in much of the Naples
area is of the slightly permeable type and produces artesian ground-
water heads.


18






REPORT OF INVESTIGATIONS NO. 11


or be equivalent to part of the Fort Thompson formation, which was
deposited during one of the glacial stages of the Pleistocene.
The Anastasia formation exhibits a lack of uniformity in deposi-
tion similar to that of the Tamiami formation. The only correlatable
unit is a hard fossiliferous tan to gray limestone which is the shal-
lowest water-bearing limestone in the Naples area. According to
information received from well drillers, this limestone bed of the
Anastasia formation is often encountered within 10 feet of the surface
in adjacent areas east of the Gordon River and causes very difficult
drilling. In test well 117 this stratum occurs 20 feet below the surface
and is about 15 feet thick. The same hard limestone was noted in
well 123 between 36 and 44 feet below the surface. It is reported
that this water-producing rock was penetrated at about 28 feet in
well 110, but the precise thickness there is not known. In the western
and southern parts of the peninsula the rock is very thin or missing
as a result of erosion during pre-Pamlico time.
PAMLICO SAND AND LATER DEPOSITS
The Naples area is entirely blanketed by the terrace deposits of
the Pamlico sand which in places is mixed with Recent black mucky
sands. The altitude of the terrace is everywhere less than 25 feet.
The Pamlico sand is composed of fine to medium sand, the base of
which lies at a depth of 10 to 15 feet below mean sea level. The
uppermost material is white or light gray medium-grained quartz
.sand which grades downward to highly colored rust-brown fine-
grained quartz sand. The color is apparently the result of the vertical
migration of organic materials in percolating ground water. The
components of the Pamlico sand are sufficiently well sorted to permit
the ready intake of rainfall and to allow easy downward percolation.
The Pamlico sand will supply small quantities of water to shallow
sand-point wells.

GROUND WATER
PRINCIPLES OF GROUND-WATER OCCURRENCE
Ground water is stored in .the openings, solution cavities, and
pore spaces within the consolidated and unconsolidated materials of
the earth's crust. The openings or voids between particles vary in
size because of the nonhomogeneous character of the sediments. The
frequency and the size of the openings determine the porosity, which
is expressed as the ratio of the volume of the interstices to the volume
of rock mass (Meinzer, 1923, p. 19). Clay is one of the most porous


13






REPORT OF 'INVESTIGATIONS NO. 11


Discharge
The effects produced by withdrawing water from an artesian well
are similar to those produced in a nonartesian well. However, dis-
charge from an artesian well results in a lowering of the pressure
at the well rather than an actual dewatering of the aquifer. Water
is released from storage, owing to the compaction or squeezing of sedi-
ments when the artesian pressure is lowered, and to slight expansion
of the water itself. The basic principle of the cone of influence re-
mains in effect, but the drawdown and spreading of the cone occur at
a more rapid rate because the amount of water released from storage
per unit area is much smaller than the amount that drains from the
pores of the rocks when the water table is lowered.
During periods of low rainfall the water table in the southern part
of the Naples area declines to elevations below the pressure surface
of the shallow artesian aquifer. A pressure differential is then set
up whereby water may move from the lower aquifer to the higher
aquifer, especially in areas where the confining layer is thinnest or
most permeable. The rate at which the movement occurs will depend
on the gradient between the aquifers, but in general the seepage will
be small. During normal times the water table is above the piezo-
metric surface of the shallow artesian aquifer, and any movement
through the confining bed is downward into the artesian aquifer.
A part of the ground water lost from the shallow artesian aquifer
is also due to natural seepage. The aquifer slopes off to the west
and the south, extending for an undetermined distance beneath the
Gulf of Mexico. The discharge occurs by upward seepage through
the confining bed, or by direct discharge where and if the aquifer
crops out on the floor of the Gulf.
Recharge
The shallow artesian aquifer accepts recharge from rainfall in
Naples and vicinity, and as seepage from overlying water-bearing
beds that may, in some cases, be at a considerable distance from
the city. Figures 5 and 6 are hydrographs of wells 107 and 88, re-
spectively, showing the correlation between water levels and rainfall.
Both wells penetrate the shallow artesian aquifer and their water
levels respond to rainfall in the area. The water levels in well 107
are effected by well-field pumping so that the plotted points in figure
5 represent daily highs and lows throughout most of 1948 and the
first three months of 1949. Appreciable rainfall at Naples is always
accompanied by a rise in the water level in shallow artesian wells.
Such rises in the water level may be the result of recharge percolating








20 FLORIDA GEOLOGICAL SURVEY


to the aquifer, or may be due to the pressure effects from the weight
of water added to the nonartesian aquifer. An attempt was made
to correlate the occurrence of rainfall at Bonita Springs, 15 miles


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REPORT OF INVESTIGATIONS No. 11 21


north of Naples, with rises in water levels at Naples, but no definite
conclusion could be drawn. Slight rises on the hydrograph (as for
example on February 9, 1948) might be correlated with rain at Bonita


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SAYONI #1 INOIJ O'dIdIOy&






FLORIDA GEOLOGICAL SURVEY


Springs when no rainfall was recorded at Naples, but these rises may
be due instead to a decrease in barometric pressure. Figure 6 is a
similar correlation of rainfall with water levels at well 88. The
water level in this well is influenced by tides and shows plots of daily
highs and lows.
Seepage of ground water from the nonartesian aquifer through the
confining layer to the shallow artesian aquifer is one of the sources
of recharge. Although proceeding at a relatively slow rate, seepage
occurs over a wide area and may be substantial. The lowering of
pressure which accompanies pumping from the shallow artesian aquifer.
increases the gradient between the nonartesian and the shallow arte-
sian aquifers, and more rapid inter-aquifer seepage results. Seepage
rates vary from place to place owning to differences in gradient be-
tween the two aquifers and in thickness and permeability of the con-
fining layer.
A part of the recharge enters the shallow artesian aquifer in an
undetermined area north or northeast of Naples where the aquifer
is probably overlain by permeable sand. The source of recharge from
the north is indicated by the general southward direction of ground-
water flow.
PRINCIPAL ARTESIAN AQUIFER
The upper part of the principal artesian aquifer underlying the
Naples area and vicinity is composed of limestone of the Tampa forma-
tion and permeable limestones and shell beds in the lower part of
the overlying Hawthorn formation (Stringfield, 1936, p. 132). Well
115 drilled to a depth of 540 feet, is the deepest artesian well of
record in the Naples area, and may penetrate the Tampa formation.
The piezometric surface in this well is about 20 feet above the land
surface. Stringfield (1936, p. 166) lists a 400-foot well at the Naples
Hotel as penetrating the Hawthorn formation. The piezometric surface
in this well measured 18 feet above the land surface in 1934.
A higher water-bearing limestone occurs within the Hawthorn
formation and yields water to wells ranging in depth from about 200
feet to 250 feet. The piezometric surface in tightly cased wells at
these depths is approximately at the land surface. This limestone
may be a poorly connected part of the principal artesian aquifer or
it might possibly be a separate artesian system.
Recharge to the artesian aquifer occurs where it is at or near the
surface, as in central Florida, and in areas where sinkholes penetrate
the Hawthorn formation, as in Polk County (Stringfield, 1936, pp.


22








REPORT OF INVESTIGATIONS NO. 11


23


O~UR E
riOL)


EXPLANATION
12 WATER-LEVEL CONTOUR
CONIOUR INTERVAL, 0.1 FOOT


Contour map of water levels in the Naples area, February 12, 1952,
showing the effect of concentrated pumping in the golf course.


FIGURE 7.







24 FLORIDA GEOLOGICAL SURVEY






















00 0













tj R.













































2/ 5 WATERLEVEL CONTOUR
N '
74


%.45 4






OA Avg SOUT

EXLNTO
1.- AE -EE O TU


FIGURE 8.


Contour map of water levels in the Naples area, March 12, 1952.









REPORT OF INVESTIGATIONS No. 11 25



















-44

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aObF' GOULF2











S2





















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-44






EXPLANATION
2 5-" WATER-LEVEL CONTOUR





FLORIDA GEOLOGICAL SURVEY


146-148, pl. 12). Water levels in wells 'penetrating the principal
artesian aquifer show seasonal fluctuations in and near recharge areas
that are due to variations in rainfall. However, rainfall at Naples
does not affect the artesian pressure in wells tapping the aquifer.
Water from the flowing wells is of little economic importance to the
area because it contains about 2,000 ppm of chloride.

WATER-LEVEL FLUCTUATIONS
Water levels in the shallow artesian wells at Naples respond to
recharge by rainfall and discharge by pumping, fluctuate with changes
in atmospheric pressure, and are affected by tides in the Gulf of
Mexico. On occasions, water levels in these wells are disturbed by
distant earthquake shocks.
Figures 7, 8, and 9 are contour maps showing water levels in the
Naples area on different dates (table 6), when the municipal wells
were not pumping. It is apparent from the relatively uniform head
that the water is derived from the same aquifer regardless of the
divergence in the depth of the wells. The piezometric surface has a
slight but regular gradient to the south, indicating recharge from the
north and discharge to the south. The contours in general appear
to conform to the topography of the area, which is more typical of
nonartesian than of artesian conditions. However, it is understand-
able because, as mentioned, seepage occurs through the confining bed
and the heads of both shallow aquifers tend to become equalized.
Water-level measurements for the contour maps were made after
recovery from pumping was essentially complete. A cone of influence
has formed north of the well field (fig. 7) as a result of pumping
irrigation wells 79 and 80 at the total rate of 500 gallons per minute.
This withdrawal concentrated within a small area is reflected by the
lowering of water levels in the northernmost city supply wells.
Figures 10 and 11 are water-level contours in the Naples area after
several hours of pumping in the city well field, and represent water
levels at periods of peak withdrawals during the winter season and
after a long period of drought in the spring. Figure 10a, in addition,
shows pumping and nonpumping water-level profiles across the penin-
sula on February 11-12, 1952, and demarks the position of the Gulf
tide at the time of the measurements. Measuring water levels in
pumped wells is generally not accepted procedure because, owing to
loss of head (well loss) as water enters and moves up a well, the
water level at the well does not reflect the true water level in the
vicinity. However, if the head losses in all wells are assumed to be


26







REPORT OF INVESTIGATIONS NO. 11


-2,0o


ECAPLANAT ION
2e5 WATER-LEVEL CONIOUR
CONTOUR INTERVAL, 0.25 rooT

kCALE IN FEET
S6O--fW-Thib0


15111 jI\AyE. 0..


FIGURE 10. Contour map showing the effect of well-field pumping on water
S levels in the Naples area, February 11, 1952.


27


.1 .25






FLORIDA GEOLOGICAL SURVEY


the same, a map based on pumping water levels indicates the general
attitude of the piezometric surface and the adjustments in the direc-
tion of ground-water flow. The adjustments are noted at the north
end of the well field, where the higher contour lines bend southward,
suggesting that recharge enters from the north.
Long-range water-level records are not available for the Naples
area; therefore no yearly comparisons can be made. The only useful
data are presented in the hydrographs in figures 5 and 6 and the
measurements in table 6 from which the contour maps were prepared.
These data show the seasonal rise and decline of water levels, and
in addition they show in a general way the difference in water levels
in shallow artesian wells and wells penetrating the nonartesian aquifer
such as well 110.
Throughout part of the year the water table in the southern part
of the well field is higher than the shallow artesian head, at times
being half a foot to a foot higher. During the period December through
May the water table declines more rapidly than the artesian level,
so that after the long period of low rainfall and high evapotranspira-
tion the nonartesian aquifer in the southern part of the well field is
drained to a point where the water-table elevation falls below the
artesian head. At the end of May 1952 the water table ranged between
0.75 and 1.0 foot lower than the artesian water level in the Naples
well field. However, in areas of higher ground elevation the water
table remains higher than the artesian head throughout the year.
During May 1952 the water table in the northern part of the well field
ranged from 1 foot to 1.5 feet higher than the artesian level.
Tidal fluctuations in the Gulf of Mexico are reflected in the water
levels in nonartesian wells near the shoreline and in shallow artesian
wells at greater distance from the shore. Ground-water fluctuations
due to tides are caused in three ways (Brown, 1925, p. 50): (1) by
transmission of pressure through the pore spaces and cavities which
connect the well to the Gulf; (2) by changes in the rate of normal
ground-water flow from the aquifer to the Gulf; and, (3) by deforma-
tion of the material resulting from alternate loading and unloading
on the earth's crust. The principle is the same in the first two, the
main difference being the rate at which the ground-water level fluc-
tuations occur. The effect of the deformation of sediments may or
may not contribute to ground-water fluctuations; the amount of effect
produced depends upon the competence of the limestone.
From the short period of tidal data available at Naples, a maximum


28









REPORT OF INVESTIGATIONS No. 11 29



range of about 4 feet between high and low tides has been recorded

in the Gulf. The water level in well 88 fluctuates with tides and lags

approximately 12 hours. The daily fluctuation ranges from 0.2 to
4 I


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FLORIDA GEOLOGICAL SURVEY


0.7 foot, but some of the effect is due to nearby pumping. The maxi-
mum range in daily fluctuation recorded at well 130 was 0.9 foot.
The water level in this well also is influenced to some extent by
well-field pumping. Although not definitely established, it is probable
that the effect of tides reaches the municipal supply wells.

SALT-WATER ENCROACHMENT
Salt-water encroachment into the fresh-water aquifers may occur
from two sources: (1) direct movement inland from the Gulf of
Mexico and from Naples Bay; and, (2) upward .contamination from
salt water which occurs at greater depth. The salt water at depth
exists either trapped in the sediments at the time of deposition, or as
water that entered the sediments at times when the sea covered the
Naples area during Pleistocene time.
The quantity of water that can be drawn from the fresh-water
aquifers in the Naples area is governed by the amount that ground-
water levels can be lowered without producing accelerated vertical
movement of high-chloride water from underlying sources or lateral
movement from the Gulf or Naples Bay. Because of a lower specific
gravity, the fresh-water body floats on top of the salt water, and
the depth to the salt water is related to the height of the fresh water
above mean sea level. This relationship, which is simply that of
a U-tube whose 2 limbs contain liquids of different density, is referred
to as the Ghyben-Herzberg principle (Brown, 1925, pp. 16-17) and
is expressed as:
t
h=
h ..___t
g-1
where h is the depth of fresh water below mean sea level, t is the
fresh-water level in feet above mean sea level and g is the specific
gravity of the salt water. If it is assumed that the specific gravity
of the sea water is 1.025, a common value, then for each foot of fresh
water which occurs above sea level, 40 feet of fresh water extends
below mean sea level. The relationship applies strictly only to static
conditions, and is modified under dynamic conditions. However,
the departure is not large enough to invalidate the principle for prac-
tical use.
CONTAMINATION IN NONARTESIAN AQUIFER
The formula is directly applicable to the nonartesian aquifer which
is relatively permeable throughout and extends outward beneath
the Gulf of Mexico and Naples Bay. An average fresh-water head
of 1.5 feet above mean sea level is sufficient to prevent salt-water en-


30






REPORT OF INVESTIGATIONS No. 11
~ -- -


EXPLANATION
12 5-- WATER-LEVEL CONTOUR
CONTOUR INTERVAL, O 25 FOOT

SCALE IN FEET
56o 0 600 ,OO


I SE


FIGUI~E 11. Contour map showing the effect of well-field pumping on water
levels in the Naples area, May 26, 1952.







FLORIDA GEOLOGICAL SURVEY


croachment to a depth of 60 feet below mean sea level. Therefore,
this aquifer with a maximum depth of 55 feet below sea level is pro-
tected in areas where the water-table elevation is 1.5 feet or more
above mean sea level. In fringe areas adjacent to the Gulf and Naples
Bay the water table slopes off to near-sea-level elevations, permitting
salt water to enter the aquifer for short distances inland. This move-
ment has not been excessive. In the southern part of the city, where
land elevations average about 5 feet, the water table lies at low ele-
vations. The various boat basins dug in this area have lowered the
water table still farther so that salt water has contaminated the area
south of Broad Avenue South. Fresh ground water is available in
this part of Naples only in very shallow wells during periods of heavy
rainfall, at which time fresh water exists as a thin lens floating on
the salt water. Wells in these fringe areas cannot be pumped heavily
or continuously because salt water would be drawn in after a short
time.

Elsewhere in the city the water table has remained at sufficient
height to prevent major contamination. It must be recognized, how-
ever, that pumping from the aquifer at present is very small as com-
pared with that from the main (shallow artesian) aquifer, the largest
losses occurring from natural seepage and evaporation. If pumpage
were to increase with the advent of many new irrigation, municipal,
or industrial wells, the water table would be lowered to a point where
salt-water contamination would result and would pose a major threat.

The extent of lowering of the water table during the months De-
cember through May is the factor that determines the safe rate of
withdrawal from the nonartesian aquifer. During this period the
water table reaches its lowest levels during the year because of mini-
mum rainfall, high evapotranspiration, and increased pumping from
small irrigation wells; thus the probability of sea-water encroach-
ment is greatest.
Under present conditions at Naples, the decline of the water table
during critical times is widespread and gradual. Pumping is scat-
tered throughout the area so that no pronounced centers of withdrawal
exist and no large cones of depression are developed. Over-all declines
are very slow but progressive. Therefore, if the water table remained
long enough below the point of salt water-fresh water balance, the
salt-water encroachment would occur slowly but on a broad front.
However, there is a considerable lag between the time of lowering
the fresh-water head and the resultant movement of salt water. It is


32







REPORT OF INVESTIGATIONS NO. 11


probably the over-all, not the short-time, water level that controls the
salt water-fresh water 1:40' ratio.
The water level in well 110 was about 3 feet above mean sea
level on March 12, 1952, but by May 27, after a period of little rainfall,
the water level fell to 1.25 feet above sea level. This water-table
elevation is at the point where a further lowering of 0.25 foot would
permit salt water to move inland from the fringe areas into the lower
part of the aquifer. As encroachment into the nonartesian aquifer
occurred, the lower fresh-water aquifer would become exposed to
contamination owing to recharge through the confining cover at times
when the piezometric surface was below the water table.
The concentration of chloride in areas near the Gulf and Naples
Bay is influenced by tides, increasing at high tides and decreasing
at low tides, and by storms. When ground-water levels inland are
high, only a narrow segment of land adjacent to the Gulf and Bay is
affected. As the ground-water level falls, a progressively wider lateral
zone is subject to fluctuation in chloride. A high tide of 2.5 feet above
mean sea level was recorded on September 2, 1951, and on October 2,
during a squall, a high of 3.1 feet above mean sea level occurred.
Along vith the flooding of the southern part of Naples, sea water
backed up into the Gordon River and raised the water levels in
tributaries, causing salty water to flow laterally into the permeable
materials.
The water from several wells tapping the nonartesian aquifer
was analyzed for chloride content and showed low concentrations
denoting little salt-water movement (see tables 2, 7, and fig. 12).
Water samples were collected also from the bottom of the various
lakes in the area, and along the Gordon River. The chloride concen-
tration in the lakes ranged from 5 parts per million at the lake south
of the golf course to about 1,420 ppm at the lake west of the well field
between First and Third Streets. The latter lake drains to the Gulf
through a control at First Street and Fifth Avenue North. Prior to
the installation of the control the lake may have been subject to some
reverse flow from the Gulf during very high tides or during dry times
when the water table approached mean sea level. The high chloride
content in this lake is probably due to the accumulation of sea water
which became land locked prior to the installation of the dam.


33








34 FLORIDA GEOLOGICAL SURVEY


TABLE 2
Chloride concentration in water samples
from selected wells at Naples
Depth of well,
Well In feet, Date Chloride
No. below land surface ppm
76 65 Aug. 8, 1951 560
Nov. 2, 1951 565
Nov. 26, 1951 610
Jan. 4, 1952 665
Feb. 28, 1952 510
Apr. 14, 1952 705
May 27, 1952 735
99 60 Sept. 26, 1951 253
Jan. 18, 1952 400
Apr. 14, 1952 528
May 27, 1952 500
100 42 Sept. 26, 1951 102
Jan. 18, 1952 96
Apr. 29, 1952 93
May 2', 1952 118
105 83 Sept. 26, 1951 110
Nov. 2, 1951 101
Nov. 26, 1951 103
Jan. 18, 1952 126
Feb. 28, 1952 133
Apr. 14, 1952 130
May 27, 1952 133
119 611 Jan. 15, 1952 14
80 Jan. 16, 1952 17
100 Jan. 16, 1952 181
103 Jan. 17, 1952 210
108 Jan. 17, 1952 452
113 Jan. 17, 1952 550
Feb. 28, 1952 605
Apr. 15, 1952 605
May 27, 1952 615
124 55+ Mar. 11, 1952 105
Apr. 30, 1952 113
June 4, 1952 127
Chloride samples collected at various depths during drilling.

The Gordon River was sampled from the Tamiami Trail bridge
crossing to a point about 2 miles upstream. The samples, which
were collected during high tide when the chloride concentration is
highest, increased southward from 11,500 ppm to 13,400 ppm. The
ground-water levels at the time of collection (February 12, 1952)
were relatively high for that part of the year so that during normal
years the chloride would probably show a still higher concentration.
Little encroachment has occurred in areas adjacent to the Gordon
River because the river is shallow, and its floor is silted up and







REPORT OF INVESTIGATIONS No. 11


clogged with organic matter. Also, the water table in areas adjacent
to the river probably has remained sufficiently high to retard encroach-
ment.
CONTAMINATION IN SHALLOW ARTESIAN AQUIFER
The elevation of the piezometric surface in the shallow artesian
aquifer, rather than the water table in the nonartesian aquifer, controls
the depth at which salt water occurs in the lower fresh-water aquifer.
The maximum depth of the municipal wells is 93 feet below mean
sea level; therefore, an average fresh-water head of more than 2.25
feet above mean sea level is required to retard the movement of the
salt front in the shallow artesian aquifer. As noted during the con-
trolled drilling of test well 119 (table 2), the chloride concentration
in the artesian aquifer increased markedly at about 92 feet below
mean sea level (100 feet below land surface). At the time of drilling,
the nonpumping water level in supply wells at the well field stood
at an average elevation of about 2.5 feet above mean sea level. The
depth at which high chloride actually occurred and the depth at which
high chloride content is predicted from the Ghyben-Herzberg formula
apparently check to within a few feet.
The water samples taken in the interval between 100 feet and 113
feet below the land surface in well 119 were collected with a bailer
because the rock material was too low in permeability to supply
sufficient water to a pump. This indication of low permeability sug-
gests the possibility that the brackish water at that depth might
represent Pleistocene sea water trapped in sediments of low perme-
ability.
The lower fresh-water aquifer as penetrated in test well 123 is
composed almost entirely of limestones of variable permeability from
about 70 feet to 145 feet below mean sea level. The water level in
this well at the time of drilling was about 4 feet above mean sea level.
Highly mineralized ground water was not' encountered at the bottom
of the well. Therefore, it may be assumed that the Ghyben-Herzberg
principle applies throughout the Naples area.

The aquifer underlies the entire Naples area and extends west-
ward beneath the Gulf of Mexico, possibly cropping out at an unde-
termined distance from the shoreline. Salt-water contamination
apparently has taken place along the western fringe and in the
southern part of the area, and chloride analyses from well 105 (table
2) indicate slight encroachment in the lower part of the aquifer west
of the well field. Encroachment in the south and in the vicinity of


35






FLORIDA GEOLOGICAL SURVEY


the Gulf is the result of direct lateral movement of sea water into
the aquifer and perhaps some seepage from the contaminated parts
of the nonartesian aquifer through the confining bed. The deeper
contamination in the aquifer inland probably is due in part to lateral
movement and also to upward migration of highly mineralized water
which remained trapped in the deep sediments at the time of deposi-
tion or has become trapped since.
The salt water interface is a fluctuating front that slowly advances
inland, or rises from below the aquifer, when ground-water levels
fall owing to pumping or low rainfall; conversely, it slowly moves
seaward and is depressed when fresh-water levels rise. Maximum
seasonal encroachment occurs during January through May when
the decline in fresh-water levels, due to the lack of recharge by rain-
fall, is further accelerated by the near-capacity operation of munici-
pal and irrigation wells. If sufficient recharge is not available to
balance the quantity withdrawn, a persistent, slow, inland, and up-
ward movement of the salt front occurs.
The hydrograph in figure 6 shows the reason for the salt-water
contamination in the south. The average water levels for January
and April 1952 were about 1.6 feet above mean sea level and were
further lowered during May 1952. If the estimated average water
level through April and May was 1.5 feet, then salt water would
occur at 60 feet below sea level. The measured depth of well 88 is
73 feet below sea level; thus, the well penetrates a contaminated por-
tion of the aquifer (table 7).
Wells 76, 99, 105, and 119, (table 2) are excellent index wells for
observing changes in chloride. The water samples from well 76, near
the Gulf, show an over-all increase in chloride content. The progres-
sive increase in chloride as noted in the analyses of samples from well
105 gives evidence of definite movement of brackish water into the
lower portion of the aquifer. This well, located midway between the
Gulf and the well field, and well 119 at the well field, are good indices
to determine the extent of salt-water encroachment in the lower part
of the aquifer.
QUALITY OF WATER
Eighteen ground-water samples were collected at Naples for com-
plete or partial chemical analyses. The principal chemical con-
stituents found in these samples are given in table 3. Four of the
analyses are of water from the nonartesian aquifer, and the remainder
represent water from the shallow artesian aquifer.


36






REPORT OF INVESTIGATIONS No. 11 37

Few major variations are noted in the water from the two aquifers
except in fringe areas near the salt-water bodies and inland at depths
greater than 100 feet below mean sea level where the water becomes
relatively highly mineralized. The high mineralization is due pri-
marily to an increase in sodium and calcium chloride and bicarbonate,
which is accompanied by an increase in hardness. High mineralization
occurs in both aquifers in the southern part of the city. In the fringe
areas and in the southern part of Naples the mineralization is prob-
ably due to sea water mixing with fresh ground water. However, the
high mineral content noted in the sample from the bottom of well 119
at a depth of ,113 feet, may represent Pleistocene sea water trapped
in relatively impermeable material. This is suggested by the fact
that the principal cation in this sample is calcium whereas the prin-
cipal cation in the water from wells 76, 88, and 99 is sodium. The
high calcium content and the increase in total hardness may denote
alteration of Pleistocene sea water trapped in relatively impermeable
limy sediments. Also, the increase in silica content may signify a
difference in the original composition of the Pleistocene sea water,
as compared with modern sea water.

Ground-water samples taken from wells more distant from sources
of contamination contained less than 250 ppm of dissolved solids. The
dissolved-solids content of the nonartesian water is apparently higher
than that of the water from the lower fresh-water aquifer.

Water having a hardness of less than 60 ppm is rated as soft; be-
tween 60 and 120 ppm, moderately hard; and 120 to 200 parts, hard.
Water having a hardness of more than 200 ppm ordinarily requires
softening for most uses. Ground water from the well-field area has
a hardness of less than 200 ppm, most of which is due to calcium bi-
carbonate and is removable by means of relatively simple treatment.
Hardness tends to increase to the east and south of the well field.

Iron in quantities of more than a few tenths of one ppm is an
objectional constituent in water (Collins and Howard, 1928, p. 181).
In addition to causing a disagreeable taste, it quickly discolors plumb-
ing fixtures and other objects with which it comes in contact to a
reddish-brown color. Many home owners in the Naples area have
experienced this discoloration on their property. The content of iron
seldom can be predicted. It differs from place to place and may also
vary with depth in the same location. Iron in water to be used for
public consumption can be removed by aeration and filtration. The
results for iron in table 3 represent iron in solution and do not in-








TABLE 3
Analyses of water from selected wells at Naples
(All results are in parts per million except those for color, pH, and specific conductance)


Well 76 Well 88 Well 99 Well 105 Well 111 Well 112


Silica (SiO,) ....................................
Iron (Pe)1 ........................................
Calcium (Ca) -....................................
Magnesium (Mg) .............................
Sodium (Na) ...................................
Potassium (K).............................
Carbonate (CO3) ..............................
Bicarbonate (HCOC ) ......................
Sulfate (S04) ...................................
Chloride (C1)...............................
Fluoride (F) .................................
Nitrate (NO ) .....................................
Dissolved solids ................................
Total hardness as CaCO, ................
Color ...................................................
pH .--.....---..---....----------------........... .----
Specific conductance
(micromhos at 25 C.) .................
Date of collection ..........................
Depth of sample (feet
below land surface) ....................
Aquifer ............................................


7.2
2.3
117
27
309
6
0
300
45
558
0.1
1.2
1,370
402
160
7.5


2,250
Mar. 26, 1953

65
Artesian


7.8
1.9
102
30
273
6
0
250
56
508
0
1.1
1,230
378
110
7.4


2,040
Mar. 26, 1953

78
Artesian


8.7
2
134
9.1
172
1.5
0
250
24
368
0
1.1
967
372
110
7.4


1,580
Mar. 26, 1953

60
Artesian


............
1.9
92
6

68
0
224
17
142
............
0.5
............
254
120
7.5


821
Mar. 26, 1953

83
Artesian


9.4
0.04
62
4
10
0.5
0
206
6.5
12
0.4
0.5
220
171
27
7.9

332
Aug. 16, 1951

76
Artesian


12.0
0.48
61
3
7.7
0.8
0
198
6
10
0.2
0.6
212
164
26
7.6


316
Aug. 16, 1951

68
Artesian


0






C4
cI









TABLE 3- continued


Well 116 Well 116 Well 117 Well 117 Well 117 Well 118
F.G.S. W-3046* F.G.S. W-3046 F.G.S. W-3041 F.G.S. W-3041 F.G.S. W-3041 F.G.S. W-3040


Silica (SiO2) ..............................
Ir on ( m e Mg) ...............................
Ironi (Fe)c ....................................

Calcium (Ca ) ............................
Magnesium (Mg) .....................
Sodium (Na) ...............................
Potassium (K) ...........................
rbionate (C3O) ..............................
icarbonate (HCO) ..... .........
ulfate ( 4) ---------------------.........
(orie (Cl) ...................................
P ride (F) ....................................
N itrate (NO) ..................................
D dissolved solids ............... ..................
Total hardness as CaCO3 ................
Color ... .......................................
H ...i ......... ..................................
Specific conductance
(micromhos at 25 C.) ............
-Date of collection ...................
Depth of sample (feet
below land surface) .................
Aquifer ............................


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

26

0
200
5.5
28
............
0.5
............
152
............
7.5

379
Jan. 3, 1952

30-36
Nonartesian


17
0.29
62
6.4
8.6
0.3
0
218
3.5
13
0.4
0.5
240
181
22
7.9

355
Jan. 4,1952

62-70
Artesian


7.2

0
238
4.5
14
............
0.3
............
204

............
7.6


390
Jan. 5, 1952

23
Nonartesian


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

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

9.4

0
252
4.5
11

0.8
............
212

7.8


401
Jan. 9, 1952

23-40
Nonartesian


11.0
0.02
59
4.5
8
0.8
0
197
3.5
11
0.5
0.5
............
166
22
7.9

320
Jan. 10, 1952

63-78
Artesian


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

49

0
314
4.5
62
............
1

244

............
7.7


644
Jan. 11, 1952

40
Nonartesian


1 Rock cuttings are filed in the sample library of the Florida Geological S urvey, Tallahassee, Florida, under this number.


Z














TABLE 3- continued


Well 118
F.G.S. W-3040


Silica (SiO ) .................................
Iron (Fe) ......................... ...........
Calcium (C ) ....................................
Magnesium (Mg) ............ ..................
Sodium (Na) ...................................
Potassium (K) ..................................
Carbonate (CO ) .............................
Bicarbonate (HCO ) .....................
Sulfate (SO ) ...................................
Chloride (C1) .................................
Fluoride ().................................
Nitrate (NO.) .................................
Dissolved solids ..............................
Total hardness as CaCO3 ...............
Color ..................................................
pH ........................................................
Specific conductance
(micromhos at 25 C.) .................
Date of collection ...............................
Depth of sample (feet
below land surface) .................
Aquifer ............................................


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


17
0
262
4.5


............
0.9

216
............
7.7

456
Jan. 11, 1952

46
Artesian


Well 118
F.0.S. W-3040


11.0
0.10
69
3
8.8
0.6
0
218
4.5


0.1
0.5
241
184
45
7.8

368
Jan. 14, 1952

70
Artesian


Well 119
F.G.S. W-3042


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

4.4
0
142
1.0
8.5
............
0.2
............
120
............
8.0

238
Jan. 15, 1952

62
Artesian


Well 119
P.G S. W-3042


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



7.6
0
200
2.5
14
............
0.3
............
170
............
8.2

339
Jan. 16, 1952

80
Artesian


Well 119
P.G.S. W-3042
34.0
0.00
181
29
125
3.4
0
246
6.5
448
0.1
0.5
963
570
29
7.7

1,740
Jan. 17, 1952

113
Artesian


Well 124


............
0.15
76
5

70
0
204
4.0
135

0.5
............
210
19
7.6


747
Mar. 26,1953

55
Artesian


. Iron in solution at time of analysis.


w


___ ~


-- I-











REPORT OF INVESTIGATIONS NO. 11


43
52-


EXPLANATION
*
WELL

CITY SUPPLY AND OTHER
WELLS OF LAROE YIELD

WELL EQUIPPED WITH
RECORDING GAGE

16
71
UPPER NUMBER IS CHLORIDE
CONCENTRATION (PPM)
LOWER NUMBER IS WELL
DEPTH (FEET BELOW LAND
SURFACE)


SCALE IN FEET
00 0 00 1,000


FIGURE 12. Naples area showing maximum chloride concentration in water
from wells of various depths, analyzed during course of investi-
gation.


Ic4






FLORIDA GEOLOGICAL SURVEY


elude iron that may have precipitated after the water was pumped
from the well.
The pH indicates the degree of acidity or alkalinity of the water.
Figures below 7.0 denote increasing acidity, and above 7.0 indicate
increasing alkalinity. The pH of samples at Naples were between
7.5 and 8.2, the greater alkalinities generally occurring in the deeper
water.
Chloride analyses were taken of samples from several wells
throughout the Naples area. These are listed in tables 2 and 7 and
are shown in figure 12, with the depth below land surface from which
the samples were collected.

QUANTITATIVE STUDIES
Three separate pumping tests were made on selected wells tapping
the shallow artesian aquifer at Naples. From water-level changes
reflected in observation wells during the tests, the coefficients of
transmissibility and storage were computed. The determinations of
the transmissibility and storage coefficients were made by the appli-
cation of the nonequilibrium method developed by Theis and de-
scribed by Wenzel (1942, pp. 87-90), and also by the method described
by Cooper and Jacob (1946, pp. 526-534).
The coefficient of transmissibility is a determination of the ca-
pacity of an aquifer to transmit water. It is expressed as the quantity
of water, in gallons per day, that will move through a vertical section
of the aquifer one foot wide under a hydraulic gradient of one foot
per foot (Theis, 1938, p. 892). The coefficient of storage expresses
the capacity of the aquifer to store water, and is the amount of water,
in cubic feet, that will be released from a vertical section of the aquifer
one foot square when the water level is lowered one foot (Theis,
1938, p. 894).
Computations are based on the following assumptions: (1) the
aquifer is without limit in a lateral direction; (2) the aquifer is homo-
geneous throughout and transmits water with equal ease in all direc-
tions; (3) the aquifer is bounded above and below by impervious
material; and, (4) no recharge enters the aquifer, and the well pumped
for the test constitutes the only discharge from the aquifer. The
characteristics of the main aquifer at Naples do not satisfy the require-
ments of an ideal aquifer. It is heterogeneous throughout, it is capped
by slightly permeable marl, it is limited by the proximity of the Gulf,
and receives recharge both from the area to the north and from the


42







REPORT OF INVESTIGATIONS No. 11


overlying material. However, the determinations for transmissibility
and storage give some valuable indications of the capacities of the
aquifer.

The first pumping test was performed on August 24, 1951 at the
municipal well field whereby well 58 was pumped for 6Y2 hours at
the rate of 62 gallons per minute. The test was of short duration
due to limited storage facilities. Water-level measurements were
taken at frequent intervals in wells 57 and 59 which are 437 feet
and 609 feet, respectively, from the pumping well. Two minutes after
pumping started the drawdown in water levels was reflected in well
57, and after nine minutes was noted in well 59. Total drawdowns
at the completion of the test were 0.42 foot in well 57 and 0.3 foot
in well 59. A recording gauge on well 107, about 2,500 feet south of
the pumped well registered a total drawdown of 0.25 foot and
the effect of pumpage reached this well after an interval of 20 or
25 minutes. The comparatively rapid response of water levels in
observation wells and the magnitude of the computed coefficient of
storage indicate the existence of artesian conditions at the well field.
Table 4 lists the results of this test and subsequent tests.
On May 6-7, 1952 a pumping test was run on the 6-inch irrigation
wells at the J. G. Sample citrus grove. Well 72 was pumped for 11
hours at the rate of 250 gpm, and then shut off to permit recovery
of the water level. Frequent water-level measurements were made
for both drawdown and recovery in wells 71, 73, 74, and 98 which
range from 575 feet to 1,075 feet from the pumped well. The effect
of pumping was reflected immediately in well 71. Total drawdowns
after 11.hours ranged from 1.88 feet in well 71 to 0.79 foot in well 98.
After 12 hours of recovery the water level returned to its pre-pumping
elevation.


TABLE 4
Results of pumping tests on wells in the
shallow artesian aquifer at Naples


Coefficient of Coefficient
Well transmissibility, of storage, REMARKS
No. T, gpd/ft. S
33 92,000 .0014 Entire city field pumping.
107 92,000 .00096 do.
57 83,000 .00038 Well 58 pumping.
59 71,000 .0010 do:
71 100,000 .00015 Well 72 pumping.
71 96,000 .00025 Recovery after pumping
well 72.
73 116,000 .00057 do.
74 129,000 .0004 do.
98 91,000 .0011 Well 72 pumping.


-----------


43






FLORIDA GEOLOGICAL SURVEY


Evidence of fluctuations in pumping rates was noted in plotting
curves for drawdown and recovery levels in observation wells. Draw-
down measurements during the test were effected by uncontrolled
variations of pumping in the grove and were influenced by with-
drawals at the municipal well field and the golf course. Also affecting
the water levels during tests were fluctuations due to tides. There-
fore, figures for transmissibility and storage computed from draw-
down measurements may not be as accurate as those determined
from the recovery test. Conditions during recovery were more con-
stant except that after approximately two hours, the effect of shutting
down of the city field was noted. The effect of the shutting down
of the city field immediately increases the quantity of water available
for recharge with the result of more rapid recovery. Recovery then
proceeded as if an imaginary well at the city field were recharging
water into the aquifer at the same rate that the well field was pumping
previously. By computation the distance from the pumped well at
the grove to the image well was 4,240 feet. If it is assumed that the
approximate center of pumping at the well field (figs. 10 and 11) is
well 33 the scaled distance between the two wells is about 4,000 feet.
Water samples were collected from well 72 throughout the duration
of pumping. Analyses of these samples did not indicate any trend
toward an increase in the concentration of chloride.
The final quantitative test was made on August 6, 1952, using the
city supply wells. The entire well field was operated at full capacity
for five hours. The average pumping rate for the duration of the
test was 616 gpm from 20 wells. Well 33 was not pumped during
the test but was used to observe water-level changes in the northern
part of the well field. An automatic gage was installed on well 107
to record water levels in the southern part of the field. The results
of this test were undoubtedly the most accurate and are indicative
of the conditions throughout the entire well field while in operation,
with no outside influences to effect water levels with the possible
exception of tidal influence.
The curves in figure 13 are plots of the drawdown in water levels
as observed in wells 33 and 107 during this test. From these changes
in water levels, computations were made to determine the composite
effect that the pumping wells produced on levels in the observation
wells after selected time intervals. These values are plotted for both
wells in figure 14 as specific drawdown (s/Q) against the logarithmic
mean of the distance (r2/t).


44






REPORT OF INVESTIGATIONS No. 11


FIGURE 13. Drawdown observed in wells 33 and 107 during pumping test on
Naples well field, August 1', 1952.

Transmissibility and storage coefficients were then determined by
the following formulas (Cooper and Jacob, 1946, p. 528):

T= 2.303 Q
4II As
S2.25 T to
r2
where T = transmissibility, s drawdown in feet, Q discharge of
well in gpm, S storage, r t distance in feet from discharge well to
observed water levels, and t = time in days. The slopes of the lines
showing the composite drawdowns in observation wells after various


0.0


0.5


I. o






c 2.0


25
W 5 --LL------ /' ---"---





3.0



50 100 IS0 200 250 300
TIME IN MINUTES AFTER PUMPING STARTED





46


FLORIDA GEOLOGICAL SURVEY


C)
z
4S



I
ho



.a
0
&
p<




t-

0
re1











04)
kO
M-






gio


B 1^
*O w


intervals (fig. 14) are parallel or very nearly parallel; thus the com-
puted transmissibility for each is 92,000 gpd per foot. However, the
offset.of the lines denotes a value of .00096 for the storage coefficient
in well 107 as compared with .0014 in well 33. In comparing these
results with those of previous tests, the cofficient of transmissibility





REPORT OF INVESTIGATIONS No. 11


falls within the same magnitude but the storage coefficient is higher.
The average transmissibility for the August 1951 and May 1952 tests
was about 98,000 gpd per foot and the average storage coefficient
was .0006.
Figure 15 presents a series of curves that represent expected
drawdowns at various distances from a pumped well after selected
time intervals. The pumpage is arbitrarily placed at 1,000 gpm or
less than twice the present rate of pumping in the Naples well field.
The curves are plotted from the Theis (1935) formula using a co-
efficient of transmissibility of 92,000 gpd per foot and a storage co-
efficient of .001. If it is assumed that a single well is discharging at
1,000 gpm at the location of well 33, the drawdown at a point 2,800
feet west of the well (edge of Gulf) after 24 hours of pumping would
be 1.7 feet. This computation for drawdown is the predicted draw-
down if the aquifer transmits water with equal facility in all directions
with the assumption that no recharge is available to the aquifer.
The following is a list of theoretical predicted drawdowns, as taken
from the graph, at various distances from a single well in the main
aquifer pumping 1,000 gpm:

DISTANCE IN FEET FROM PUMPED WELL
So
0 0 o
oo o o 0 o o 0













io




14
^y-4-----
|.^Z_ __
^y ....- --.----


FIGURE 15. Expected drawdowns at various distances from a well pumping
at a constant rate of 1,000 gpm after selected time intervals.


47






FLORIDA GEOLOGICAL SURVEY


Distance Drawdown (feet)
(feet) after
1 day 2 days
200 .......... ........................................................... 8.25 9.03
500 .............................................. ....................... 5.95 6.75
1,000 ..................................................................... 4.22 5.02
2,000 .......................................... ........................ 2.51 3.32
3,000 ......................................... ............................ 1.55 2.38
5,000 ................................................................ 0.73 1.30

The foregoing computations are based on the supposition that
only a single well is pumping at a constant rate. If withdrawals
were distributed over 10 wells, each pumping 100 gpm, and spaced
400 feet apart along the center line of the well field, the predicted
drawdown after one day at the edge of the Gulf would be 1.56 feet
or 0.15 foot less drawdown than if the total withdrawal came from
one well.
Under present operating conditions at the well field, 21 wells
pump a total of 500 gpm from the shallow artesian aquifer or an
average of 24 gpm per well. Being proportional to the rate of output,
the predicted drawdown at the Gulf beach after 24 hours is computed
at 0.78 foot or slightly less, due to the wider distribution of wells.
In analyzing the accuracy of the chosen coefficients of transmissi-
bility and storage used in figure 15, a predicted drawdown is compared
with an actual measured drawdown. On May 26, 1952 the measured
drawdown in well 117, 2,000 feet east of the center of the well-field
pumpage, was 0.6 foot after 10 hours of operation at 500 gpm. A pre-
dicted drawdown of 0.73 foot was computed after 12 hours and less
than 0.7 foot after 10 hours. Thus, the actual drawdown and the
predicted lowering check to within less than 0.1 foot.
With this relatively accurate comparison between measured and
anticipated drawdowns it was assumed that the Theis method of
computing pumping test data was sufficient for practical purposes.
Some departure in the coefficient of transmissibility would result by
using the method described by Jacob (1946 pp. 198-205), in which
leakage from the confining bed is taken into account. Owing to the
fact that the pumping tests were of short duration the ground-water
contribution to the aquifer in the form of vertical leakage is probably
relatively small, and thus would produce only a slight deviation from
the Theis curve.
As is often the case during dry periods, the irrigation wells at
the golf course and the citrus grove pump water at the same time


148







REPORT OF INVESTIGATIONS No. 11


the city well field is operating at peak. This arrangement sets up
three distinct centers of pumpage in the area. The point where the
three cones of influence intersect (greatest accumulated drawdown)
is the theoretical center of pumpage of the three withdrawal areas.
Employing figure 15 for varying distances, the point of greatest
mutual interference between the three centers is located about 100
feet east of a line connecting wells 33 and 79, midway between the
two wells. Assuming that 500 gpm is withdrawn from a single
well at each center, the accumulated drawdown at the theoretical
point of greatest interference would be 4.16 feet after 12 hours and
5.33 feet after 24 hours.
The maximum amount of water that can be pumped from the
Naples area without endangering the quality of the ground water is the
safe yield of the aquifer. The nearest source of salt water is the
Gulf of Mexico and is considered the boundary of the aquifer.
It has been previously determined that a line of 10 wells each pump:-
ing 100 gpm at the well field would produce a drawdown of 1.56
feet at the edge of the Gulf after 24 hours. From the short period
of water-level data and from figure 9, the nonpumping water level
at the well field ranged from 2.0 feet to 2.5 feet above mean sea
level at the end of May 1952 after an extended dry period, and
sloped off to 1.5 feet near the western edge of the peninsula. Using
this range in water levels as a low or a near low of record it is readily
seen that after 24 hours of continuous pumping at 1,000 gpm the
ground-water level at the western edge of Naples would decline to
mean sea level, and after 12 hours at the same rate the water level
would fall to 0.8 foot above mean sea level.

The lowering of ground-water levels to mean sea level at the
Gulf indicates that the safe yield of the aquifer is being exceeded.
This is not meant to imply that as soon as the fresh-water head
falls below the critical 2.0 foot level set up by the Ghyben-Herzberg
formula, the well field will be immediately contaminated. Actually
salt water moves first into the lower part of the aquifer and along
the fringes of the peninsula. The movement of ground water is
naturally slow, depending upon the gradient, so that contamination
would occur gradually but probably with a consideralle time lag.
If lowering were induced by pumping over a period of days, the
encroachment would be accelerated due to the steeper ground-water
gradient. However, when pumping stops, rising fresh-water levels
force the salt water interface back toward its original position. Thus,
the safe yield of the aquifer may be exceeded only for short periods.


49







FLORIDA GEOLOGICAL SURVEY


If exceeded over long periods the aquifer will become permanently
contaminated.
GROUND-WATER USE
In the several years prior to 1945 the development of the Naples
area remained nearly static. Ground-water withdrawals were small
and supplies were relatively undeveloped. A large percentage of
water was pumped from privately owned wells. One 6-inch well
and two 4-inch wells west of the water plant, ranging in depth from
80 to 84 feet, produced the water supply for the city. The wells
eventually yielded brackish water because of close spacing and ex-
cessive local lowering of the ground-water levels. The present
water-supply system was developed in 1945 when the rapid growth
of the city of Naples created a demand for a dependable water supply.
The supply was obtained from 10 wells of 3-inch diameter, tapping
the shallow artesian aquifer, each equipped with a small centrifugal
pump. Pumpage was restricted to not more than 30 gpm from each
well. The wells were spaced about 400 feet apart so that the pump-
ing effect was distributed over a relatively large area and drawdowns
were slight. With the large increase of population from 1946 to 1951,
12 additional wells were drilled. Eleven of these are 4 inches in
diameter and penetrate the shallow artesian aquifer; the last, well
110, is a 6-inch well developed in the nonartesian aquifer. Similarly,
the pumping rates of these wells are restricted so that average out-
puts are usually below 30 gpm per well during peak seasons. The
spacing of these wells is also approximately 400 feet. The entire
well field is spread over an area of about 65 acres.
Figures of total pumpage from the well field are available since
1946 and are presented in table 4. The peak months of water usage
are December through April which coincides with the height of the
tourist season. During these months the population at Naples nearly
doubles. In addition, this is a period of low rainfall and increasing
need for irrigation water.
Irrigational use is one of the largest drains on the ground water
supplies. Most private homes in the area irrigate with small-diameter
wells that penetrate either the nonartesian or the shallow artesian
aquifer. Approximately 100 of these wells are in operation during
the period of low rainfall, and even when they are pumped only
3 or 4 hours daily their combined pumpage amounts to a considerable
percentage of the total groundwater withdrawal. In the southern
part of the city the shallow aquifers produce salty water and the


50













TABLE 5
Pumpage from Naples well field in millions of gallons per month


Year


Jan.


Feb.


Mar.


Apr.


May


June


July


Aug.


Sept.


Oct.


Nov.


Dec.


1946 .............. ...... ...... ...... 4.802 2.40 1.58 1.82 1.82 1.41 2.54 2.41 2.12
1947 ............. 3.48 3.78 4.37 3.92 3.05 1.60 1.64 1.94 1.65 1.97 2.59 3.33
1948 ..-------.. 3.42 4.93 6.31 3.86 3.56 3.24 2.15 1.95 2.41 3.44 5.76 5.52
1949 ............. 6.83 7.16 7.71 5.54 4.37 2.43 2.39 2.51 2.24 2.76 3.28 5.04
1950 .............. 7.02 6.86 8.60 7.20 5.503 4.44 3.08 3.48 4.12 3.99 5.15 4.624
1951 .............. 6.505 7.506 9.30 5.71 7.46 6.70 3.87 3.84 3.77 4.20 7.22 9.07
1952 ..............11.55 9.79 12.327 11.27 9.09 5.68 5.15 8.04 5.18 4.62 8.38 10.04


1 Fiigres are approximate.
2 Twelve wells in operation.
s Estimate.
SThirteen wells in operation.
5 Fifteen wells in operation.
Seventeen wells in operation.
7 Twenty-two wells in operation.


0










(
0
z







FLORIDA GEOLOGICAL SURVEY


municipal supply is used for irrigation as well as household needs. A
few residents in this area have reverted to partial irrigation from
flowing wells penetrating the principal artesian aquifer. According
to some owners this high-chloride water is fairly satisfactory for
irrigating some grasses.

The largest withdrawal of water for irrigation is made at the
golf course, which is supplied by pumping three 6-inch wells (wells
78, 79, and 80) and one 8-inch well (well 136) that penetrate the
shallow artesian aquifer. These wells are piped together into a
single system serviced by one pump of 500- to 600-gpm capacity.
When irrigation is required, the wells operate 5 to 8 hours per day.
To be noted again in figure 7 is the marked effect produced in the
northern part of the well field by the heavy pumping in the golf
course area.

Considerable quantities of water for irrigation are pumped from
five 6-inch wells at the J. G. Sample citrus grove in the eastern part
of the city. Each well is capable of yielding 200 to 300 gpm from
the shallow artesian aquifer, and during dry seasons some of the
wells may pump continuously for 3 or 4 days.


SUMMARY
In the Naples are and most of Collier County the principal artesian
aquifer contains salty water. At the town of Everglades near the
southern edge of Collier County, however, the principal artesian
aquifer yields water containing less than 300 ppm of chloride to
some flowing wells. The shallow artesian and nonartesian aquifers
yield fresh water to wells at shallow depths throughout most of the
county and are used for irrigation, domestic, and public supplies.
In the vicinity of Ochopee, 35 miles southeast of Naples, and much
of the area south of the Tamiami Trail, the shallow aquifers contain
salty or brackish water.
The shallow artesian aquifer at Naples is composed of part of
the Tamiami formation, and in northwestern Collier County it in-
cludes shell beds in the upper part of the Hawthorn formation. The
less permeable marls of the Tamiami formation form a confining
layer above the shallow artesian aquifer. At present few data are
available for north-central and east-central Collier County concern-
ing the variation in depth, thickness, and capacities of the fresh-
water aquifers.


52







REPORT OF INVESTIGATIONS No. 11


With the exception of the city of Naples, no area in Collier County
shows any indication of overdraft of the ground-water reserves. The
original municipal well field at Naples was abandoned after the
shallow ground water in the southern part of the city became salty
because of heavy pumping and declining ground-water levels. The
present well field is similarly subject to contamination, and sampling
of ground water reveals that some encroachment of salt water has
taken place in the lower part of the shallow artesian aquifer. Pump-
ing tests indicate that, because of the proximity of salt water, the
safe yield of the shallow artesian aquifer can be exceeded only for
short periods of pumping, and that contamination will occur during
dry periods if ground-water levels are not permitted to recover
sufficiently each day.

As existing well-field facilities have already reached peak ca-
pacity, further development has been proposed for the area to the
north, in the direction indicated by the test-drilling program. Of
prime importance in the development of additional ground-water
supplies is a location where the pumping will have the least effect
on the ground-water levels in the present area of withdrawal, and
to obtain water from the nonartesian aquifer as well as the shallow
artesian aquifer. Results of pumping tests and predictions of draw-
downs in wells provide data useful in locating and spacing new wells
penetrating the shallow artesian aquifer. These data, however, prob-
ably are not indicative of the aquifer as a whole. This fact is borne
out by the variation in the results of various pumping tests.

The most favorable sites for additional ground-water supplies are
in areas where: (1) the aquifers are thickest; (2) pumping will
least affect water levels in the present well field; (3) there is least
danger of salt-water contamination (farthest from the source of salt
water); and, (4) ground-water levels remain sufficiently high
throughout the year to prevent salt-water encroachment. These
areas, so far as known at this time, include sites 0.7 mile to a mile
north or northeast of the golf course.

Dredging of boat basins in the southern part of the city has
caused lowering of the ground-water levels in that area, thus per-
mitting accelerated salt-water encroachment. The digging of drain-
age canals results in a rapid decline of ground-water levels, which
may extend back into the recharge areas. Drainage ditches have
caused serious problems of salt-water encroachment in other parts
of south Florida, notably in the Miami area.


53







54 FLORIDA GEOLOGICAL SURVEY

Much valuable information concerning the capacities and the
development of the fresh-water aquifers in Collier County can be
gained through the continuous gathering of such basic data as water-
level fluctuations, changes in chloride concentration, and pumpage
records. Water-level observations in both equifers made on a con-
tinuing basis, and regular chloride analyses of water from key wells
taken at the beginning and end of periods of well-field pumping, more
frequently during critical months, will permit determining the extent
of overdevelopment of the ground-water resources, the quantity of
usable ground water available, and the approximate position of the
salt-water front.








55


REPORT OF INVESTIGATIONS No. 11
TABLE 6


Water levels, in feet, referred to mean sea level
(p denotes pumping level)

Well Date Water Well Date Water
No. level No. level


11-12-51
11-26-51
11-27-51
3-12-52
5-26-52
5-27-52

11-12-51
11-26-51
11-27-51
2-11-52
2-12-52
3-12-52
5-26-52
5-27-52

11-12-51
11-26-51
11-27-51
2-11-52
2-12-52
3-12-52

2-11-52
2-12-52
3-12-52
5-26-52
5-27-52

11-12-51
11-26-51
11-27-51
2-11-52
2-12-52
3-12-52
5-26-52
5-27-52

11-12-51
11-26-51
11-27-51
2-11-52
2-12-52
3-12-52
5-26-52
5-27-52

11-12-51
11-26-51
11-27-51
2-11-52
2-12-52
3-12-52
5-26-52
5-27-52


0.91p
0.66p
3.41
3.02
-0.87p
2.11

0.93p
0.65p
3.37
0.16p
3.10
3.00
-1.26p
2.11

0.59p
0.30p
3.38
0.30p
3.08
2.99

0.50p
3.13
3.04
-0.91p
2.07

0.78p
0.50p
3.38
0.67p
3.08
2.99
-1.41p
2.12

0.70p
0.39p
3.41
0.26p
3.09
3.02
-1.01
2.13

0.97p
0.69p
3.58
0.64p
3.21
3.14
-0.77p
2.21


31







32





33







56







57







58







59


11-12-51
11-26-51
11-27-51
2-11-52
2-12-52
3-12-52
5-26-52
5-27-52

11-12-51
11-26-51
11-27-51
3-12-52
5-26-52
5-27-52

11-12-51
11-26-51
11-27-51
2-11-52
2-12-52
3-12-52
5-26-52
5-27-52

11-12-51
11-26-51
11-27-51
2-11-52
2-12-52
3-12-52
5-26-52
5-27-52

11-12-51
11-26-51
11-27-51
2-11-52
2-12-52
3-12-52
5-26-52
5-27-52

11-12-51
11-26-51
11-27-51
2-11-52
2-12-52
3-12-52
5-26-52
5-27-52

11-12-51
11-26-51
11-27-51
2-11-52


0.78p
0.46p
3.47
0.16p
3.14
3.04
-1.18p
2.14

0.55p
0.20p
3.33
2.89
-1.32p
2.09

-0.37p
-0.58p
3.64
-1.63p
3.21
3.18
-2.96p
2.27

1.llp
0.89p
3.72
0.60p
3.22
3.25
-0.80
2.33

1.65p
1.31p
3.72
1.07'p
3.20
3.24
-0.35p
2.34

0.93p
0.66p
3.57
0.36p
3.14
3.11
-0.96p
2.23


1.88p
1.69p
3.84
1.62p


27




28







29







30







FLORIDA GEOLOGICAL SURVEY


TABLE 6- continued

Well Date Water Well Date Water
No. level No. level

2-12-52 3.16 108 11-12-51 2.18
3-12-52 3.32 11-26-51 1.90
5-26-52 0.06p 11-27-51 3.66
5-27-52 2.44 2-11-52 1.79
2-12-52 3.28
60 11-12-51 1.55P 3-12-52 3.22
11-26-51 1.63p 5-26-52 -0.57p
11-27-51 3.95 5-27-52 2.17
2-11-52 1.46p
2-12-52 3.12 109 11-12-51 1.77
3-12-52 3.45 11-26-51 1.47
5-26-52 0.01p 11-27-51 3.42
5-27-52 2.55 2-11-52 0.72p
2-12-52 3.15
3-12-52 3,02
61 11-12-51 1.41p -26-52 --1.02p
11-26-51 1.64p 5-27-52 2.06
11-27-51 4.04
2-11-52 1.18p 110 11-12-51 3.73
2-12-52 3.02 11-26-51 3.60
3-12-52 3.53 11-27-51 3.61
5-26-52 -0.31p 2-11-52 3.28p
2-12-52 3.53
62 11-12-51 2.08p 3-12-52 2.98
11-26-51 2.05P 5-26-52 0.71p
11-27-51 3.98 5-27-52 1.25
2-11-52 1.51p
2-12-52 3.12 111 11-12-51 1.71
3-12-52 3.47 11-26-51 1.41
5-26-52 1.02 11-27-51 3.56
5-27-52 2.58 2-11-52 1.30
2-12-52 3.21
78 11-12-51 1.58 3-12-52 3.31
5-26-52 -0.17
11-26-51 3.32 5-27-52 0.18
11-27-51 4.17-2 2 21
2-11-52 3.1' 112 11-12-51 2.06
2-12-52 2.30 11-26-51 1.78
3-12-52 3.43p 11-27-51 3.71
5-26-52 1.60 2-11-52 1.OO
2-11-52 1.OOp
5-27-52 2.74 2-12-52 3.16
3-12-52 3.21
79 11-12-51 -4.81p 5-26-52 0.37p
11-26-51 3.31 5-27-52 2.34
11-27-51 4.15
2-11-52 3.17 116 2-11-52 3.02
2-12-52 -1.07p 2-12-52 2.85
3-12-52 3.59 3-12-52 3,19
5-26-52 1.58 5-26-52 1,78
5-27-52 1.12p 5-27-52 2.38







57


REPORT OF INVESTIGATIONS No. 1.1


TABLE 6 continued


Well Date Water Well Date Water
No. level No. level

117 2-11-52 1.89 5-26-52 1.22
2-12-52 2.40 5-27-52 1.57
3-12-52 2.21
5-26-52 0.87 119 2-11-52 0.80
5-27-52 1.47 2-12-52 0.90
5-26-52 -.0.31
5-27-52 1.74
118 2-11-52 2.38
2-12-52 2.58 123 5-26-52 2.67
3-12-52 2.30 5-27-52 3.36






TABLE 7
Records of selected wells at Naples


Well Pla. Sample
No. Library No..


Owner


Driller


Year
com-
pleted


Dia-
Depth meter
(ft.i i n.


City of Naples
do.
do.
do.

do.

do.
do.
do.
do.
do.

J. L. Kirk
City of Naples
do.
do.
do.
do.
do.
do.
J. Prince
Naples
Supply Co.
J. Pulling
do.
do.
City of Naples

W. R. Rosier
Trail's End
Motel
J. G. Sample
do.
do.


29
30
31
32
33


38
56
57
58
59
60
61
62
63
64

65
66
67
68

69
70

71
72
73


J. Maharrey
do.
do.
do.

do.

do.
do.
do.
do.
do.

A. Cooper
J. Maharrey
do.
do.
do.
do.
do.
do.

J. ~aharrey

Jenkins
do.
do.
J. Maharrey

J. Pulling
..........

J. Maharrey
do.
do.


1945
1945
1945
1945


43
43
28
28


41
1945 63 3 60 28
25
1945 63 3 60 28
1945 63 3 60 17
1945 73 3 71 28
1945 98 3 92 63
1945 95 3 93 13


1951
1949
1949
1950
1950
1950
1950
1950
1930
1950

1939
1939
1939
1950


42
74
76
75
88
92
82?
70-
27
65-70

33
33
33
90


1951 63
1951 75


1945
1945
1949


60+
52+-
434-


2
4
4
4
4
4
4
4
1Y2
3

4
4
2
4


40
67
65
69
83
88
7*8
70



26?
26
30
75


1M2 60
4 70

6
6 ....
6


8- 7-51
8- 7-51
8- 7-51
7-31-46
8- 7-51
7-31-46
8- 7-51
8- 7-51
8- 7-51
8- 7-51
12-31-52
8- 7-51


168 8-
16 8-
12 8-


15
13
12
12
19
19
28


32
11
13
25
29


34
41


9-51
7-51
7-51


8- 7-51
8- 7-51
8- 7-51
8- 7-51
11-26-51
11-26-51
1-18-52


8- 8-51
11-26-51
5-27-52
8- 8-51
11-26-51


5- 6-52
8-23-51


PS.
P.S.
P.S.
P.S.

P.S.


PS.
P.S.
P.S.
P.S.
PS.

Irr.
P.S.
P.S.
P.S.
P.S.
P.S.
Ps.


P.S.
PJS.


Dom.
Ind.

Irr.
Irr.
Stock
School

Dom.
Irr.


Irr.
Irr.
Irr.


See table 6
do.
do.
do.


do.


do.
do.
do.
do.
See tables 4, 6 and
figs. 13, 14

See table 6
See tables 4 and 6
do.
do.
See table 6
do.
do.


See table 4
do.
do.


Casing
depth
Ift.,


ppm.


Chloride


Date


Use,


REMARKS


MC

0



8



HS


__


__~







TABLE 7- continued


Well Fla. Sample
- No. Library No.


Owner


Driller


Year
corm-
pieted


Dia-
Depth meter
(ft.) (in.)


Casing
depth
(ft.)


Chloride
ppm. Date


74
75
76
77


do.
do.
J. Townshend
do.

J. Maharrey

do.
do.


C. Rivers

do.


do.
do.
Tibbett' Estate
Fleiscbhmann
Estate
Naples Co.

do.
do.

City Ice Co.
Neopolitan
Enterprises
L. A. Oricks

R. Lehman
City Ice Co.

do.

B. W. Morris

J. G. Sample
A. D. Miller
J. E. Turner
C. J. Sumarall
R. O. Clark
H. C. Peterson

W. T. Truesdale

do.
W. Storter
City of Naples


1949
1949
1950
1950

1930

1930
1930


50+
62+
65
55


6

63 6
63 6


60
50 364
362
14
12
.... 24
.... 14


1930 73
1951 63


1949 52 2 50 19
31
1936 72 2 70 18
........ 73 3 70 .

1922 78 4 .... 458
465
1950 46? 3 .... 58
48
1949 52+ 6 .... 43
1950 60 2
1950 42 2 40
1949 42 11/2 40 15
1950 42 2 40 14
1950 42 2 40 113
80
1951 63 2 60 27
34
1951 83 2 78
1949 45 11/4 .... 442
1951 66 3 60


8- 8-51
4-29-52
8- 8-51
3- 6-52
3-12-52
5-27-52


Irr.
Irr.
Irr.
Irr.

Irr.


Irr.


Ind.
............ I d.
8- 8-51 Dom.,
Irr.
8- 8-51 Irr.


5-27-52
8- 9-51


4-15-52
5-27-52
8-22-51
5-27-52
8-23-51


9-26-51
9-26-51
9-26-51
4-29-52
9-26-51
5-27-52

9-26-51
............


Irr.
Ind.,
Irr.
Obs.

Irr.

Irr.
Irr.
Irr.
Irr.
Irr.
Irr.

Irr.

Irr.
Irr.
Obs.


do.

See tables 2 and 3


See table 6

do.
Composite sample with
well 79







See fig. 6, table 3


See table 4
See tables 2 and
See table 2


3


Cd

0




01




I-


See tables 2 and 3

See figs. 5, 13, 14 and ,
table 4


C. Rivers

J. Maharrey
A. Cooper
J. Townshend

A. Cooper
do.

do.

do.
J. Townshend
J. Maharrey


79
80


81
82

83

86
87

88

97


Usel


REMARKS


98
99
100
'1-01
102
103

104

105
106
107


--


18







TABLE 7- continued


Well P.l. Sample
No. Library No.


Owner


Driller


Year
com-
pleted


Dme-
Depth meter
tft. I I in. )


108
109
110

111
112
114

115


116 W-3046

117 W-3041
118 W-3040
119 W-3042

123 W-3045

124

125

126


127

128
129
130

136


W-3044


City of Naples
do.
do.

do.
do.
Beldin

City of Naples

U. S. Geological
Survey
do.
do.
do.

do.

A. DiMeola

H. M. McClaskey

H. C. Sherier

L. P. Grimes

R. L. Williams
F. W. Dreher
U. S. Geological
Survey
Naples Co.


J. Maharrey
do.
do.

do.
do.
P. Duke

J. Maharrey

Miller Bros.

do.
do.
do.

do.

C. Rivers

A. Cooper

do.

do.

J. Maharrey
C. Rivers
Miller Bros.

J. Maharrey


1951
1951
1951

1951
1951
1951


71

40

77
68
245


59

27

74
66
235


16
31
15
16


4510


1939 540 5 300 2300
2160
1952 71 2 62


1952
1952
1952


78
70
113


1952 157


63
69
112


2 97


1949 55+ 1/2 50

1951 40 + 1/2 40 3

1951 42 11/2 40


1951 46 1IY


1951
1951
1952


60?
40+
71


2
1Y2
6


10-11-51
10-12-51
10-12-51
4-30-52

11-13-51

11-13-51
3-24-52
............


P.S.
P.S.
P.S.


See table 6
do.
do.


P.S. See tables 3 and 6
P.S. do.
Irr. Water level slightly
above land surface
Fire Water level approx. 20
ft. above land surface
Obs. Test well; see log and
tables 3 and 6


............ Obs. do.
.... ............ Obs. do.
.... ............ Obs. Test well; see log and
tables 2, 3, and 6
............ Obs. Test well; see log and
table 6
.... ............ Dom., See tables 2 and 3
Irr.
318 4-29-52 Irr.


242
16
17


.... 214
192
27
40 34
69 148


5-27-52
4-29-52
5-27-52
4-29-52
5-27-52
4-29-52
4-29-52
6-10-52


1952 90 8 84+


frr.

frr.


Irr.
Irr.
Obs.


Recording gage


............ Irr.


P.&-PubLlc tPPMly
frr.-mIngation
Dom-Domestic
Ibs.-Iiervatriso
Obs.-Obsrvaton


Casing
depth
S ft. I


Chloride


ppm.


Date


Usel


REMARKS







FLORIDA GEOLOGICAL SURVEY


municipal supply is used for irrigation as well as household needs. A
few residents in this area have reverted to partial irrigation from
flowing wells penetrating the principal artesian aquifer. According
to some owners this high-chloride water is fairly satisfactory for
irrigating some grasses.

The largest withdrawal of water for irrigation is made at the
golf course, which is supplied by pumping three 6-inch wells (wells
78, 79, and 80) and one 8-inch well (well 136) that penetrate the
shallow artesian aquifer. These wells are piped together into a
single system serviced by one pump of 500- to 600-gpm capacity.
When irrigation is required, the wells operate 5 to 8 hours per day.
To be noted again in figure 7 is the marked effect produced in the
northern part of the well field by the heavy pumping in the golf
course area.

Considerable quantities of water for irrigation are pumped from
five 6-inch wells at the J. G. Sample citrus grove in the eastern part
of the city. Each well is capable of yielding 200 to 300 gpm from
the shallow artesian aquifer, and during dry seasons some of the
wells may pump continuously for 3 or 4 days.


SUMMARY
In the Naples are and most of Collier County the principal artesian
aquifer contains salty water. At the town of Everglades near the
southern edge of Collier County, however, the principal artesian
aquifer yields water containing less than 300 ppm of chloride to
some flowing wells. The shallow artesian and nonartesian aquifers
yield fresh water to wells at shallow depths throughout most of the
county and are used for irrigation, domestic, and public supplies.
In the vicinity of Ochopee, 35 miles southeast of Naples, and much
of the area south of the Tamiami Trail, the shallow aquifers contain
salty or brackish water.
The shallow artesian aquifer at Naples is composed of part of
the Tamiami formation, and in northwestern Collier County it in-
cludes shell beds in the upper part of the Hawthorn formation. The
less permeable marls of the Tamiami formation form a confining
layer above the shallow artesian aquifer. At present few data are
available for north-central and east-central Collier County concern-
ing the variation in depth, thickness, and capacities of the fresh-
water aquifers.


52







RtEPo oRTO INVESTPGATIONs No, 11


WELL LOGS
WELL 116
(P.G.S. Sample Library No. W-3046)
Southwest corner of Third Street and South Golf Drive, Naples, Florida
Depth, in feet,
Description below land surface
Sand, quartz, fine to medium, white to tan, becoming brown
in lower part .......................... ............ ..................0... 20
Sand, quartz, fine to very fine, brown .................................... 20- 25
Limestone, sandy, fossiliferous, tan to gray; permeable........ 25 42
Marl, sandy, tan to gray; becomes very shelly in lower part.... 42 52
Lim estone, sandy, gray .................................................................. 2- 55
M arl, sandy, white to gray .......................................... ......... .. 55- 61
Limestone, sandy, fossiliferous, gray; permeable..................... 61- 70
Sand, marly, fine to medium, gray ............................................ 70 71

WELL 117
(F.G.S. Sample Library No. W-3041)
North side of Fifth Avenue, North, east of Tamiami Trail, just
west of Atlantic Coast Line Railroad, Naples, Florida.
Depth, in feet,
Description below land surface
Sand, quartz, fine to medium, white to tan grading to
brown at base ....... ....................................................... ......... 0- 15
Sand, quartz, very shelly, white to tan; with few fresh-
water gastropod shells .......................................... .......... 15- 19
Limestone, sandy, fossiliferous, very hard, tan; permeable.. 19- 34
Limestone, sandy, fossiliferous, tan to gray, softer than
above; perm eable ................................................. .......... 34 40
Sand, fine, shelly, gray to greenish ......................................... 40 45
Limestone, sandy, gray, fossiliferous ........................... ... 45- 47
Sand, marly, shelly, gray to greenish ........................................ 47- 54
Limestone, sandy, gray ............................................................. 54 57
Marl, sandy, shelly, gray to green .............................. .... 57 64
Limestone, sandy, fossiliferous, gray to tan; permeable .......... 64 78

WELL 118
(F.G.S. Sample Library No. W-3040)
Five hundred feet west of Naples water plant, Naples, Florida.
Depth, in feet,
Description below land surface
Sand, quartz, fine to medium, white to gray becoming rust-
brown in lower part ............................................... ........ 0 21
Limestone, sandy, shelly, tan ...... .............................. ........... 21- 22
Sand, fine, marly, very shelly, tan to cream ............................... 22- 34
Sand, tan, fine, very shelly ............................................. 34 38
Limestone, sandy, fossiliferous, gray to tan; permeable........ 38 40
Marl, sandy, very shelly, gray to tan .............................. 40 45
Limestone, sandy, fossiliferous, gray; permeable .................... 45- 47







FLORIDA GEOLOGICAL SURVEY


Marl, sandy, very shelly in lower part, gray ............................ 47 54
Limestone, sandy, gray .............................................................. 54 56
Marl, very sandy, gray ................................................... ....... 56 64
Limestone, sandy, fossiliferous, gray, hard; permeable ........ 64 70
WELL 119
(F.O.S. Sample Library No. W-3042)
Depth, in feet,
Description below land surface
Fifty feet west of well 31, Naples well field, Naples, Florida.
Sand, quartz, fine to medium, white to tan, changing to
brown in lower part ....................................................... 0- 20
Marl, sandy, shelly, tan to cream ............................................. 20- 25
Limestone, sandy, shelly, tan to gray ............ ........................... 25- 27'
Sand, quartz, shelly, fine, tan to gray ........................................ 27 32
Limestone, sandy, fossiliferous, tan to gray .............................. 32 38
Marl, sandy, shelly, gray to green ................................................ 38- 56
Limestone, sandy, fossiliferous, gray; permeable .................. 56- 71
Marl, sandy, gray, with thin interbed of soft limestone ........ 71 78
Limestone, sandy, fossiliferous, gray; permeable .................... 78-83
Marl, very sandy, gray to green, becoming cream to white in
lower part; contains thin interbeds of hard, fossiliferous
lim estone .................................................................................. 83 113
WELL 123
(F.G.S. Sample Library No. W-3045)
Seven-tenths mile north of South Golf Drive, and 150 feet west
of Tamiami Trail in city dump area, Naples, Florida.
Depth, in feet,
Description below land surface


Sand, quartz, medium to fine, white to tan, grading to rust-
brown in lower 10 feet ..................................... ............
Limestone, sandy, shelly, tan................................................
Marl, very sandy, shelly, tan ..................................... .............
Marl, similar to above, contains fresh-water gastropods ........
Sand, quartz, medium, shelly, tan ............................:.................
Limestone, sandy, fossiliferous, tan to gray, very hard;
perm eable .............................................................. ..............
Limestone, very sandy, tan, soft, contains few fossils; perme-
able ...................................................... ...................................
Limestone, partially cemented, sandy, shelly, tan to light
g reen ...........................................................................................
Marl, very sandy and shelly, gray to green .................................
Limestone, sandy, fossiliferous, gray to green; a sand-filled
cavity at 69 feet; permeable ..................................................
Marl, sandy, very shelly, gray to green; heaves badly ............
Limestone, sandy, fossiliferous, cream to white; permeable....
Marl, sandy, cream to white; occurs as a cavity filling or
thin bed ............................................ ................... ................
Limestone, sandy, slightly fossiliferous, cream to yellowish-
green; with cavity fills or thin interbeds of marl or cal-


0- 26
26 28
28 32
32 34
34 36

36 44

44 54

54 60
60 63

63 71
71 82
82 107

107- 109


62








REPORT OF INVESTIGATIONS NO. 11


careous sand .............................................................................. 109 138
Marl, sandy, cream; as cavity filling or thin bed .................... 138 141
Limestone, partly cemented, sandy, fossiliferous, and cream
m arl, sandy ............................................................................ 141 157




BIBLIOGRAPHY
BROWN, J. S.
1925 A study of coastal ground water with special reference to Con-
necticut: U. S. Geol. Survey Water-Supply Paper 537, pp. 14-17,
34-37, 49-53.
COLLINS, W. D.
1928 (and HOWARD, C. S.) Chemical character of waters of Florida:
U. S. Geol. Survey Water-Supply Paper 596-G, pp. 181-185.
COOKE, C. WYTHE (also see PARKER, G. G.)
1945 Geology of Florida: Florida Geol. Survey Bull. 29, pp. 111-113,
144, 210-212, 238-243.
COOPER, H. H.
1946 (and JACOB, C. E.) A generalized graphical method for evaluating
formation constants and summarizing well-field history: Am.
Geophys. Union Trans., vol. 27, no. IV, pp. 526-534.


HOY, N. D.
1952


JACOB, C. E


(and SCHROEDER, M. C.) Geology and ground-water resources of
Lee and Charlotte Counties, Florida: (unpublished manuscript in
preparation).
".


1946 Radial flow in a leaky artesian aquifer: Am. Geophys. Union
Trans., vol. 27, no. 2, pp. 198-205.
MANSFIELD, W. C.
1939 Notes on the upper Tertiary and Pleistocene mollusks of penin-
sular Florida: Florida Geol. Survey Bull. 18, pp. 11-16.
MATSON, G. C.
1913 (and SANFORD, SAMUEL) Geology and ground waters of Florida:
U. S. Geol. Survey Water-Supply Paper 319.
MEINZER, .O. E.
1923 Outline of ground-water hydrology: U. S. Geol. Survey Water-
Supply Paper 494, pp. 17-28, 32-50, 60-63.
1932 The occurrence of ground water in the United States with a dis-
cussion of principles: U. S. Geol. Survey Water-Supply Paper
489, pp. 2-8, 28, 52-53.
PARKER, G. G.
1944 (and COOKE, C. WYTHE) Late Cenozoic geology of southern Flor-
ida, with a discussion of the ground water: Florida Geol. Survey
Bull. 27, pp. 56-67, 74-75.
1950 (and STRINGFIELD, V. T.) Effects of earthquakes, trains, tides,
winds, and atmospheric pressure changes on water in the geologic
formations in southern Florida: Econ. Geology, vol. 45, no. 5,
pp. 441-460.


63






FLORIDA GEOLOGICAL SURVEY


1951 Geologic and hydrologic factors in the perennial yield of the
Biscayne aquifer: Jour. Amer. Water Works Assn,, vol. 43, no.
10, p. 819.
STRINGFIELD, V. T. (also see PARKER, G. G.)
1936 Artesian water in the Florida peninsula: U. S. Geol. Survey Water-
Supply Paper 773-C, pp. 127-132, 146-148, 166-167, and pl. 12.
THIS, C. V.
1935 The relation between the lowering of the piezometric surface and
the rate and duration of discharge of a well using ground-water
storage: Am. Geophys. Union Trans.. pp. 519-524.
1938 The significance and nature of the cone of depression in ground-
water bodies: Econ. Geology vol. 33, no. 8, p. 894.
VERNON, R. O.
1951 Geology of Citrus and Levy Counties, Florida: Florida Geol. Sur-
vey Bull. 33, pp. 186-187.
WENZEL, L. K.
1942 Methods for determining permeability of water-bearing materials:
U. S. Geol. Survey Water-Supply Paper 887, pp. 87-90.


64








REPORT OF INVESTIGATIONS NO. 11


careous sand .............................................................................. 109 138
Marl, sandy, cream; as cavity filling or thin bed .................... 138 141
Limestone, partly cemented, sandy, fossiliferous, and cream
m arl, sandy ............................................................................ 141 157




BIBLIOGRAPHY
BROWN, J. S.
1925 A study of coastal ground water with special reference to Con-
necticut: U. S. Geol. Survey Water-Supply Paper 537, pp. 14-17,
34-37, 49-53.
COLLINS, W. D.
1928 (and HOWARD, C. S.) Chemical character of waters of Florida:
U. S. Geol. Survey Water-Supply Paper 596-G, pp. 181-185.
COOKE, C. WYTHE (also see PARKER, G. G.)
1945 Geology of Florida: Florida Geol. Survey Bull. 29, pp. 111-113,
144, 210-212, 238-243.
COOPER, H. H.
1946 (and JACOB, C. E.) A generalized graphical method for evaluating
formation constants and summarizing well-field history: Am.
Geophys. Union Trans., vol. 27, no. IV, pp. 526-534.


HOY, N. D.
1952


JACOB, C. E


(and SCHROEDER, M. C.) Geology and ground-water resources of
Lee and Charlotte Counties, Florida: (unpublished manuscript in
preparation).
".


1946 Radial flow in a leaky artesian aquifer: Am. Geophys. Union
Trans., vol. 27, no. 2, pp. 198-205.
MANSFIELD, W. C.
1939 Notes on the upper Tertiary and Pleistocene mollusks of penin-
sular Florida: Florida Geol. Survey Bull. 18, pp. 11-16.
MATSON, G. C.
1913 (and SANFORD, SAMUEL) Geology and ground waters of Florida:
U. S. Geol. Survey Water-Supply Paper 319.
MEINZER, .O. E.
1923 Outline of ground-water hydrology: U. S. Geol. Survey Water-
Supply Paper 494, pp. 17-28, 32-50, 60-63.
1932 The occurrence of ground water in the United States with a dis-
cussion of principles: U. S. Geol. Survey Water-Supply Paper
489, pp. 2-8, 28, 52-53.
PARKER, G. G.
1944 (and COOKE, C. WYTHE) Late Cenozoic geology of southern Flor-
ida, with a discussion of the ground water: Florida Geol. Survey
Bull. 27, pp. 56-67, 74-75.
1950 (and STRINGFIELD, V. T.) Effects of earthquakes, trains, tides,
winds, and atmospheric pressure changes on water in the geologic
formations in southern Florida: Econ. Geology, vol. 45, no. 5,
pp. 441-460.


63










FLRD GEOLOSk ( IC SUfRiW


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