Citation
Hydrology of western Collier County, Florida ( FGS: Report of investigations 63 )

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Title:
Hydrology of western Collier County, Florida ( FGS: Report of investigations 63 )
Series Title:
( FGS: Report of investigations 63 )
Creator:
McCoy, H. J ( Henry Jack )
Geological Survey (U.S.)
Florida -- Bureau of Geology
Place of Publication:
Tallahassee
Publisher:
State of Florida, Dept. of Natural Resources, Division of Interior Resources, Bureau of Geology
Publication Date:
Language:
English
Physical Description:
32 p. : illus. ; 23 cm.

Subjects

Subjects / Keywords:
Hydrology -- Florida -- Collier County ( lcsh )
Naples (Fla.) ( lcsh )
City of Naples ( local )
Collier County ( local )
Big Cypress ( local )
Gulf of Mexico ( local )
Henderson Creek ( local )
Canals ( jstor )
Aquifers ( jstor )
Rain ( jstor )
Counties ( jstor )
Water quality ( jstor )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Bibliography: p. 32.
Statement of Responsibility:
by Jack McCoy, prepared by U. S. Geological Survey in cooperation with Collier County, City of Naples [and] Bureau of Geology, Florida Department of Natural Resources.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier:
024797506 ( ALEPH )
01335132 ( OCLC )
AAM7946 ( NOTIS )

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STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
Randolph Hodges, Executive Director



DIVISION OF INTERIOR RESOURCES
Robert 0. Vernon, Director



BUREAU OF GEOLOGY
Charles W. Hendry, Jr., Chief




Report of Investigations No. 63



HYDROLOGY OF
WESTERN COLLIER COUNTY, FLORIDA



By
JACK McCoY



Prepared by
U.S. GEOLOGICAL SURVEY
in cooperation with
COLLIER COUNTY
CITY OF NAPLES
BUREAU OF GEOLOGY
FLORIDA DEPARTMENT OF NATURAL RESOURCES


TALLAHASSEE, FLORIDA
1972










CONTENTS

Page
-Abstract ----------------- 1
Introduction ----------------------- 1
Purpose and scope of investigation--------------- 1
Previous investigations ------- ----- 3
Acknowledgments --------------------------------------------- 3

General features ------------------------------------------------- 4
Climate ---------------------------------------6
Physiography and drainage ------------------------------------- 6

Water problems -------------------------------------------------- 7

Hydrology ------------------------------------------------------ 9
Surface flow system ------------------------------------------- 9
Shallow aquifer ---------------------------------------------14
Recharge and discharge ------------------------------------ 16
Hydraulic properties -------------------------------------- 21
Floridan aquifer ---------------------------------------------23

Water quality -----------------------------------------------23
Natural constituents -------------------------------------- 23
Surface water ------------------- 23
Ground water ---------------- --- 27
Contaminants -------------------- 27
Natural ----------------------- 28
Man-made --------------- ---------- 28

Water use ---------------------------------------------------- 28

Summary and conclusions ------------------- 29

Well logs -------------------------------------------------------30

References --------------------------------------------------- 32






ILLUSTRATIONS

Figure Page
I Map of Florida showing location of Collier County ------ 2

2 Location of area of investigation ------ 4

3 Physiographic regions of Collier County (after Davis, 1943, figure 1) 7

4 Map of the Big Cypress Watershed showing flow directions in Decem-
ber, 1969 (after Klein and others, 1970, figure 3) ------------------ 8

5 Canal system in western Collier County showing location of weirs and
discharge stations --------------------------------------------10

6 Hydrographs of discharge for selected canals in western Collier
County ----------------------------------------------------- 12

7 Direction and amount of flow in the Golden Gate Canal system on
May 13 and July 22, 1969 ------------------------------------- 13

8 Generalized geologic section along line A-A' in figure 9 ------------- 15

9 Location of test holes and line of generalized geologic section -------- 17

10 Location of wells equipped with water-level recorders --------------- 19

11 Hydrographs of selected wells in western Collier County and rainfall
at Naples ----------------------------------- ----------- 20







TABLES

Table Page
1 Average monthly and 1970 monthly temperatures and rainfall at Naples 5
2 Chemical analyses of water from selected canals in western Collier
County ------------------------------------------------------ 26
3 Chemical analyses of water from selected wells in western Collier
County -------------------------------------------------- 24









HYDROLOGY OF
WESTERN COLLIER COUNTY, FLORIDA

By
Jack McCoy


ABSTRACT
Although the fresh-water-supply potential of western Collier
County is large, water problems exist in that the 54 inches of annual
rainfall are not evenly distributed throughout the year, salt-water
intrustion threatens the Naples well field during prolonged dry
periods, and contamination of existing and future ground-water sup-
plies is possible by man-related activities.
The controlled surface-water flow system of the GAC (Gulf
American Corporatioh) developments minimizes the threats of
floods without an excessive lowering of water levels near the coast.
Variable water quality and inadequate flows during the dry season
preclude the use of the surface-water flow system as a direct source
of municipal water.
Naples well-field expansion is limited by water of inferior qual-
ity in the shallow aquifer immediately east of the well field. The
shallow aquifer in an area starting about 11 miles inland and extend-
ing eastward to State Road 29 contains water of good quality. The
shallow aquifer extends from land surface to a depth of almost 100
feet near SR 84 and SR 951 and from land surface to more than 70
feet near SR 84 and SR 29. Available data indicate the aquifer in
this area has a capacity several times that in the Naples coastal
area.

INTRODUCTION
PURPOSE AND SCOPE OF INVESTIGATION

Collier County, in southwestern Florida (fig. 1), receives abun-
dant rainfall, 54 inches annually. The western third of the county is
underlain by permeable sediments about 100 feet thick containing
water of good quality in most places. However, water problems exist
in the county. The major problem is the development of additional
fresh water supplies to meet the demands of the rapidly growing
population. The projected rapid growth rate prompted officials to
take action not only by expanding municipal water-supply systems
but also by suggesting that investigations be made to establish








2 BUREAU OF GEOLOGY













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Figure 1.-Map of Florida showing location of Collier County.





REPORT OF INVESTIGATION NO. 63


possible new well-field sites in inland areas. The U.S. Geological
Survey was requested in 1967 to locate areas that would most likely
yield the greatest quantities of the best quality water to satisfy the
projected municipal needs of western Collier County.
The investigation included the following phases: (1) evaluation
of existing data; (2) determination of the hydrologic and geologic
characteristics of the subsurface materials; (3) collection of miscel-
laneous discharge data in the inland canal complex and interpreta-
tion of the data; and (4) determination of the quality of water.
This report was prepared by the U.S. Geological Survey in co-
operation with Collier County, the city of Naples, and the Bureau of
Geology, Florida Department of Natural Resources. The work was
under the immediate supervision of T. J. Buchanan, Subdistrict
Chief, Miami, Florida, and under the general supervision of C. S.
Conover, District Chief, Tallahassee, Florida, both of the U.S.
Geological Survey,


PREVIOUS INVESTIGATIONS
Two reports, "Ground-water resources of the Naples area, Col-
lier County, Florida, 1954", by Klein and "Ground-water resources
of northwest Collier County, Florida, 1961", by Sherwood and Klein,
summarize the geologic and hydrologic conditions in northwestern
Collier County. The report "Ground-water resources of Collier
County, Florida, 1962", by McCoy gives a general portrayal of the
geologic and hydrologic conditions throughout the county. Some
hydrologic and biologic aspects of the Big Cypress Swamp water-
shed are described in a preliminary report by Klein and others
(1970). Day-to-day variations in physical, biological (including
bacterial), and chemical character of the water flowing into, through,
and discharging from the Big Cypress Swamp watershed during
March 1970 are recorded in the report by Little and others (1970).


ACKNOWLEDGMENTS
Many public officials have contributed valuable information and
assistance during the study. Among them were W. H. Turner,
County Manager; Tom Peeke, County Engineer; and W. F. Savidge,
Director of the Naples Public Works Department. Dr. J. I. Garcia-
Bengochea and Robert Ghiotto of Black, Crow, and Eidsness, Inc.
rendered many services and courtesies.





BUREAU OF GEOLOGY


GENERAL FEATURES
Collier County consists of 2,119 square miles in the southwest-
ern part of Florida, making it the second largest county in the State.
The county is bounded on the west and southwest by the Gulf of
Mexico, on the north by Lee and Hendry Counties, on the east by
Broward and Dade Counties, and on the southeast by Monroe


Figure 2.-Location of area of investigation.






REPORT OF INVESTIGATION NO. 63


TABLE 1.-AVERAGE MONTHLY AND 1970 MONTHLY TEMPERATURES
AT NAPLES1
Temperature (*F) Rainfall (inches)
1942-1970 1970 1942-1970 1970
January 65.5 60.7 1.74 1.95
February 66.5 61.7 1.76 1.97
March 71.0 68.5 2.39 13.56
April 73.6 75.4 2.01
May 77.1 75.9 3.98 5.32
June 80.9 80.4 8.16 6.48
July 82.4 82.0 8.30 5.26
August 82.9 82.7 8.19 4.68
September 81.9 81.7 9.55 13.32
October 77.1 77.5 4.96 2.87
November 71.1 67.1 1.39 .43
December 66.6 65.7 1.25 .02
Average 74.6 73.3 54.65 55.86
1U.S. Weather Bureau, Climatological Data, 1942-1970.

County. The principal municipalities are Naples, on the west coast,
Immokalee in the north-central part, and Everglades City, on the
south coast.
The area of investigation consists of about 280 square miles in
the western quarter of the county (fig. 2). The area's boundaries
are roughly the Naples city limits on the west, State Road 846 on
the north, the Fakha Union Canal on the east, and U.S. Highway 41
(Tamiami Trail) on the south. About half the area has been platted
for single and multiple-unit dwellings by GAC (Gulf American
Corporation). Streets in nearly one-third of the platted segment
have been completed. A massive canal system has been established
by the developers to provide flood control. Weirs that have been
placed throughout the canal system to control the flow prevent ex-
cessive drainage.
Collier County was the fastest growing county in Florida during
1960-70, increasing in population from almost 16,000 to slightly
more than 38,000. In 1970, Naples and its environs accounted for
about two-thirds of the population, and the population in the area
of investigation was about 1,000, mostly residents of the Golden
Gate Estates development. Projected population for Golden Gate
Estates exceeds 50,000.
Agriculture is the principal industry in the area investigated.
Several thousand acres of Golden Gate property in the northern
part of the development is leased for growing cucumbers, water-





BUREAU OF GEOLOGY


melons, tomatoes, and peppers. Farming on a smaller scale is active
along U.S. Highway 41 also.

CLIMATE
Climate in Collier County is humid subtropical: summers are
warm and wet, and the winters are mild and dry. Total rainfall in
Naples for 1949-70 averaged 54 inches (table 1). Most of the rain-
fall occurs during June through October. The summer rains are
usually tropical, frequent, intense, and of short duration. Winter
rains are associated with weather fronts and are usually longer but
less intense, and they vary widely in frequency.
Because of the cooling effect of summer rains, the highest daily
temperature during the summer is about 950F. The lowest daily
temperature for the winter is about 340F. Cold periods usually
follow the frontal rains and do not last more than a few days at a
time. The average annual temperature in Naples is about 75F
(table 1), the summer average is 820F, and the winter average is
660F.
PHYSIOGRAPHY AND DRAINAGE
Davis (1943, fig. 1) divided Collier County into three physio-
graphic regions: The Flatlands, the Big Cypress Swamp, and the
Southwest Coast and Ten Thousand Islands (fig. 3). Most of the
investigation area lies within the Big Cypress Swamp region and
is characterized by swamps containing large cypress trees, islands
of pine forests, and wet marl prairies. Most of this region is less
than 15 feet above msl (mean sea level). The southern part of the
area lies within the Southwest Coast and Ten Thousand Island
region and contains tidal streams, bays, lagoons, and thousands of
shoal-water islands. The area south of U.S. Highway 41 is primarily
mangrove swamps and salt-water marshes.
Drainage in Collier County is determined by topographic con-
figuration and canals. Because of the flat topography and slow nat-
ural drainage, no well-defined stream system is developed except for
the Gulf Coast estuaries, where drainage is through tidal channels.
In the fresh-water environment, most drainage is through sloughs
and strands and by canals, as shown in figure 4.
Drainage in the area investigated is characterized by an exten-
sive system of controlled canals, which drain southward and west-
ward into the Gulf Coast estuaries (fig. 2). Outlets for the system
are the Golden Gate Canal at Naples and the Fahka Union Canal






REPORT OF INVESTIGATION NO. 63


Figure 3.-Physiographic regions of
figure 1).

northwest of Everglades City.
mokalee is drained to the gulf
River Canal. The Henderson
drains the southwestern part


Collier County, Florida (after Davis, 1943,


Part of the area southwest of Im-
north of Naples by the Cocohatchee
Creek Canal, southeast of Naples,
of the area investigated.


WATER PROBLEMS
In western Collier County, as in most of southern Florida, the
major water problems are:
1) Availability and protection of potable ground-water sup-
plies in vicinity of population centers.
2) Quality of water in areas of potential well-field expansion.
3) Protection of ground-water supplies from excessive drain-


0 Miles





BUREAU OF GEOLOGY


Figure 4.-Map of the Big Cypress Watershed showing flow directions in
December, 1969 (after Klein and others, 1970, figure 3).

age by flood-control practices in the expanding urban
areas, and
4) threat of contamination of potable ground-water supplies
by man-made chemicals and wastes.
Nearly all ground water for public use in western Collier County
is supplied by the city of Naples well field. The well field is less than
2 miles inland from the gulf and has always been threatened by
salt-water intrusion. Production of treated ground water from the






REPORT OF INVESTIGATION NO. 63


well field has increased from an average daily rate of 0.2 mgd (mil-
lion gallons per day) in 1950 to 4.4 mgd in 1970 and is predicted to
exceed 17 mgd by 1990. The withdrawal of 17 mgd without serious
contamination resulting from salt-water intrusion will present a
formidable problem for water managers.
Expansion of the Naples well field to the north and to the south
is extremely limited by natural salt-water contamination in the
aquifer. For about 10 miles inland the quality of the ground water
is inferior to the water in the existing well field. Therefore, develop-
ment of additional ground-water supplies will have to start in an
area at least 10 miles inland, a considerable distance from the major-
ity of the water users.
Urbanization in the inland areas required the construction of
a large canal network to lower water levels in areas historically
swampy and to prevent flooding. However, increased water needs
resulting from the urbanization will require careful management of
the canal network in order to avoid depleting ground-water supplies
because of excessive drainage.
The possibility of contaminating fresh-water supplies by man-
made wastes and chemicals continues to increase as more land is
developed. The method and degree of treatment and the location of
waste-disposal sites will have a significant effect on the quality and
the quantity of future water supplies.

HYDROLOGY
SURFACE FLOW SYSTEM

Construction of the extensive canal system shown in figure 5
was begun in the early 1960's with the excavation of the Golden
Gate Canal, the primary canal in the western part of the system.
Excavation of the Fahka Union Canal, the .primary canal in the
eastern part of the system, was begun in 1968. Several secondary
canals connect with the Golden Gate Canal, whereas the Fahka
Union Canal is the combination of four parallel primary canals. The
canal systems provide controlled drainage to permit development
of the Golden Gate Estates, east of Naples, and the Remuda Ranch
Grants, southeast of Naples. Before construction of the canals,
much of the area was inundated each year during the rainy season.
The Golden Gate Canal extends about 20 miles inland from the
Gordon River. The bottom of the canal is 5 feet below msl at its
outlet to Gordon River and 6 to 8 feet above msl in the interior. The






10 BUREAU OF GEOLOGY
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Figure 5.--Canals in western Collier County showing location of weirs and
discharge stations.






REPORT OF INVESTIGATION NO. 63


design plans for the Fahka Union Canal call for similar bottom
elevations. Distributed throughout the canal system are about 30
weirs, which increase in elevation toward the interior. The eleva-
tions of the coastal weirs on the Golden Gate and Fahka Union
Canals (numbers 8 and 24) are 3 and 2 feet above msl. The eleva-
tion of the highest interior weir (number 13 near Immokalee) is 17
feet above msl.
The function of the canals is to lower annual peak water levels
to prevent flooding during the rainy season. The function of the
weirs is to control the canal flow and reduce the possibilities of over-
drainage. During the rainy season, when water levels in the interior
are high, water moves from aquifer storage into the canals and
downstream over the weirs. At the beginning of the dry season,
flow over the inlandmost weirs ceases but continues over the down-
stream weirs. Flow over the weirs ceases in succession downstream,
as the dry season continues, until flow occurs only at coastal weirs
on the primary canals. Water has continued to flow over the coastal
weirs in both primary canals since the canals were completed. The
shallow depth of the canals and the distribution of weirs at selected
elevations within the canal system limit drainage from the shallow
aquifer in the inland areas. By limiting drainage from aquifer stor-
age, regional water levels near the coast are not lowered excessively,
and, therefore, the problem of sea-water intrusion is not magnified.
Continuous records of discharge are obtained at all outlets of
the canal system (fig. 5). Flow in the Golden Gate Canal is measured
upstream from weir W8. The record began October 1964. Flow in
Fahka Union Canal is measured upstream from weir W24, beginning
in December 1969, and in the Henderson Creek Canal, about 4 miles
south of Alligator Alley, (SR84), beginning in August 1968. Flow
in the Cocohatchee River Canal was originally measured near a
bridge on SR846 about 1 mile east of U.S. Highway 41, but channel
improvements produced tidal effects at the gaging site, and the sta-
tion was relocated to its present site in October, 1968. Hydrographs
of these four canals for the periods of record are shown in figure 6.
The Golden Gate Canal is about 100 feet wide, less than 8 feet
deep, and has several fixed weirs throughout its reach of about 26
miles; the Fahka Union Canal is similar in width and depth and
about 30 miles long; the Henderson Creek and Cocohatchee River
Canals are about 25 feet wide, less than 5 feet deep, and 7 and 13
miles in length, respectively. The Henderson Creek Canal is uncon-
trolled except for a constriction at Alligator Alley which acts as a
surface-water divide most of the time. However, at the peak of the







BUREAU OF GEOLOGY


Figure 6.-Hydrographs of discharge for
County.


selected canals in western Collier


rainy season, the Henderson Creek Canal probably receives some
flow from the Golden Gate Canal. The Cocohatchee River Canal has
a control a short distance upstream from the gaging station. Farm-
ers regulate the control according to irrigation needs. The Coco-
hatchee River Canal drains most of the area southwest of Lake
Trafford, but it also helps drain the Golden Gate area during peak
wet periods. Because of their larger channels and drainage basins,
the Golden Gate and Fahka Union Canals discharge more water
than the Cocohatchee River and Henderson Creek Canals.
The discharge of all the canals responds quickly to rainfall on
their respective drainage basins, as demonstrated by the response
to rainfall in early June, 1969. (See rainfall graph in fig. 11). On the
other hand, rainless periods produced sustained declines of all dis-
charges such as those of April and most of May 1970. Only a trace
of rainfall was recorded at Naples during April and the first three
weeks of May. The rapid decline of the flows throughout this period
suggests very little ground-water inflow. This could be due to either
low permeability of the aquifer or shallowness of canals or both.
The closeness of the water table to land surface throughout the
area of investigation, the flatness of the drainage basins, and the


12








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REPORT OF INVESTIGATION NO. 63 13
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BUREAU OF GEOLOGY


intensity of most of the rainfall requires that drainage canals in
developed areas be adequately designed to remove surplus rainfall
quickly if flooding is to be prevented. The sharp rises of .the dis-
charge peaks in figure 6 indicate the rapid removal of flood waters;
the short duration of the peaks and the rapid declines indicate that
a minimal amount of water reaches the aquifer as recharge.
During 1970 the average discharge at each of the four stations
was: (1) Golden Gate Canal, 250 cfs (cubic feet per second); (2)
Fahka Union Canal, 270 cfs; (3) Henderson Creek Canal, 25 cfs;
and (4) Cocohatchee River Canal, 15 cfs. Near the end of the dry
season in 1971, discharge at the Golden Gate Canal outlet reached
a record low of less than 20 cfs (about twice the average daily
pumpage of the Naples water system in 1970).
Figure 7 shows the direction and amount of flow in the Golden
Gate Canal system on May 13 and July 22, 1969. These periods were
representative of flow conditions near the end of the dry season and
near the beginning of the wet season, respectively. Weirs completed
at the time of the measurements are identified by a symbol and
number.
The contrast in flow on the 2 days is readily apparent, except
for the inlandmost part of the system. Also apparent is the down-
stream increase in flow on both days. On May 13 this increase re-
sulted largely from prolonged ground water seepage into the canal
from aquifer storage. Even during this driest part of the year, 91
efs, or about 60 mgd, was discharged into the tidal reach of the
Gordon River.
Flow at every measuring site on July 22 was almost 10 times
that on May 13, except for the unfinished inland part of the system,
the Cocohatchee River Canal, and the Henderson Creek Canal.

SHALLOW AQUIFER
All fresh ground water used in western Collier County for mu-
nicipal, domestic and industrial supplies, and for irrigation is ob-
tained from a shallow unconfined aquifer. The shallow aquifer is
composed of the Pleistocene terrace sands, the permeable limestones
and sands of the Pleistocene Anastasia Formation, and the upper
permeable limestones of the late Miocene Tamiami Formation (Mc-
Coy, 1962, p. 24). The aquifer is underlain nearly everywhere by a
thick section of sand or clayey limestone. The maximum thickness
of the shallow aquifer is about 130 feet in Naples, where the terrace
sands and the Anastasia and Tamiami Formations are all present














This part of section Is not
AHKA UNION CANAL shown in figure 9.

25-- R -A-(25



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LEVEL ___4 -



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BUREAU OF GEOLOGY


and have some hydraulic connection. Thickness of the aquifer varies
for several miles inland from the coast. The aquifer is usually thick-
est at the coast, thinning to the northeast, east and southeast.
Figure 8 is a generalized geologic section from Naples to SR 29
along line A-A' in figure 9. The figure shows the undulation of the
bottom of the aquifer and the presence of sand and shelly marl in
the upper 50 feet near the coast.
The permeability of the aquifer varies considerably. The lime-
stone and shell beds near the coast are permeable, and 8-inch wells
drilled in them will yield 500 gpm (gallons per minute) with 7 to 15
feet of drawdown. In the area east and southeast of Naples to about
SR 858 and SR 84, the aquifer is less permeable, and the water in it
is more mineralized. Also a localized shallow dense limestone (not
shown in figure 8) retards rainfall infiltration in much of the area
immediately east of the Naples well field, thus inhibiting the flush-
ing of residual sea water (sea water trapped in the sediments dur-
ing deposition) from the aquifer in this area. Farther inland, where
the subsurface materials are more continuous and homogeneous,
the aquifer is more permeable than it is in the coastal area, par-
ticularly from test hole 11 (fig. 9) eastward to SR 29 and north to
about Golden Gate Boulevard.

RECHARGE AND DISCHARGE
Infiltration of rainfall and seepage from controlled canals are
the means of recharge to the shallow aquifer. Recharge from rain-
fall is greatest during the rainy season, June to November. Re-
charge from canals is greatest during the dry season, December to
May, when canal levels immediately upstream from the weirs are
higher than adjacent ground-water levels.
Discharge from the aquifer is by evapotranspiration, by ground-
water flow to canals and the gulf, and by pumping from wells.
Groundwater and surface-water flow and losses by evapotranspira-
tion are greatest during and shortly after periods of rainfall, when
water levels in the aquifer are high; discharge by pumping is great-
est during dry periods, although it constitutes only a small part of
the total discharge from the area.
Changes in aquifer storage are indicated by fluctuations of the
water table. When recharge to the aquifer is greater than dis-
charge-which is usually only during a rain-the water table rises;
when discharge from the aquifer is greater than recharge--which
is most of the time-the water table declines. Fluctuations of the







REPORT OF INVESTIGATION NO. 63 17

81145' 81l30'



0 1 2 3 4 MILES

\ LEE COUNTY \



COCOHATCHEE RIVER CANAL I I i

,H .._ ..I. .304.
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County test hole o

Geologic section line ISLAND 0



81045' 8130'
Figure 9.-Location of test holes and line of generalized geologic section.





BUREAU OF GEOLOGY


water table are monitored by automatic recording instruments on
five wells shown in figure 10. Hydrographs of these wells for their
periods of record are shown in figure 11. Monthly rainfall at Naples
is included for comparison.
Ground-water-level data are not available for the area east of
Naples before the canals were constructed because the area was
flooded or swampy through most of the year, and access was very
difficult. Local lowering of levels began with the construction of the
Cocohatchee River and Henderson Creek Canals, and regional lower-
ing followed construction of the Golden Gate Canal and finally the
Fahka Union Canal. The hydrographs in figure 11 began too late to
reflect the lowering of -vater levels when canal construction started
but show the changes that occurred as construction continued. Pre-
drainage levels were above land surface much of the year, which
would indicate the canal system lowered ground-water levels 1 to 2
feet before the weirs were installed.
Wells C-384 and C-381 are located, respectively, adjacent to the
Cocohatchee River and Henderson Creek Canals near their outlets.
The hydrographs of the two wells (fig. 11), plus early periodic meas-
urements in well C-384 show that water levels in the two wells were
higher in the rainy season of 1965 than in the two previous years,
even though the 1965 rainfall was below average. This suggests
that the completion of weir W-4 and W-8 in October 1964 may have
caused the Cocohatchee River and Henderson Creek Canals to act
as relief outlets for the Golden Gate Canal system during the wet
seasons. However, as the Golden Gate Canal system was extended
inland, surface water that normally drained to the Cocohatchee
River Canal was diverted to the Golden Gate Canal system. This is
indicated by the lowering, in 1970, of the peak levels in C-384 and
the decrease in discharge of Cocohatchee River Canal. For the same
period the area around C-381 was flooded most of the time, and the
discharge of Henderson Creek Canal increased.
Wells C-383 and C-382 are within the influence of the Golden
Gate Canal system (fig. 10); but C-383 is adjacent to a narrow bor-
row ditch, and C-382 is in the urbanized section of Golden Gate
Estates and about three-quarters of a mile from the Golden Gate
Canal Since 1965, wet-season water levels in well C-383 appear to
have risen about a foot; since mid-1967 the dry-season levels have
risen about a foot also. These effects are probably the result of a
combination of (1) improvements in the canal system, which allow
the borrow canal to convey more water during the wet season, (2)
the installation of weir 10 immediately downstream from C-383, and







REPORT OF INVESTIGATION NO. 63 19

81*45' 81-30'

A

0 I 2 3 4 MILES \\

LEE COUNTY
2\1, l ,\


C \ O COHATCHEE RIVER CANAL I I 1 N


C- G8- I- I- "






I EM' I I

ma II
Canaland" i We.r. S !S --MINOE .
S TATEi- .. -J -
-.I,'l I 1- r








u 1 41 1
A rE

1P 1 0
C adW ir I I I










8GATE C 8 N "110
Figure 10.-Lcation of wells equipped with water-level recorders
"-%3~~~----- -------- ,






20 BUREAU OF GEOLOGY





I LAND SbRFACE


12 WELL C-271 I
t I I .I I l l


I I1 I LAND SURFACE
d ,Ic WELL C-384


,I I I I I I .
O-





S i Is I LAND I I I I U A
S WELL C-384







LF1 RAINFALL -
S- I I ---- Annual _----- Z
U-j






zS rn11 (z 4
S I' I LN SR 0 u
U>L' l WELL C-382 [ -6
JI u nJ J Lri


Figure 11.--Hydrographs of selected wells in western Collier County and
monthly rainfall at Naples.






REPORT OF INVESTIGATION NO. 63


(3) the above-average rainfall starting in 1967 after 4 years of
below-average rainfall. The hydrograph for well C-382 shows a gen-
erally consistent pattern for 1963-68. Except for short-term fluctua-
tions due to abnormally high or low monthly rainfall, the seasonal
water levels are generally similar. The slight rise in levels starting
in 1969 is probably the result of above-average rainfall.
Well C-271 is near the inlandmost reach of the Golden Gate
Canal. The hydrograph for the well shows little year-to-year varia-
tion before 1966. Completion of the Golden Gate Canal into the area
near the well has doubtless caused the decline in seasonal water
levels in 1967-69. Completion of the weir installations and above-
average rainfall in early 1970 are probably responsible for the
higher dry-season levels in 1969-70. Water levels in well C-271 dur-
ing the last half of 1969 and all of 1970 indicate most graphi-
cally the effects of the canal system on the water levels in the
shallow aquifer. If the trend of the last 18 months in the hydro-
graph for C-271 persists, the canal system will have been effective in
lowering wet-season levels as much as 1.5 feet and dry-season levels
about 1 foot below pre-construction levels.
In summary, the effects of the canal system on the shallow
aquifer can be only approximately evaluated at this time (1971)
because the data-gathering period since completion of weir installa-
tions is too short for detailed analysis. If trends indicated in 1969
and 1970 persist, the canal system may lower wet-season water
levels at least 2 feet and perhaps as much as 4 feet in the far in-
terior areas.
The hydrographs in figure 11 show the water level in the shal-
low aquifer fluctuates as much as 6 feet from wet season to dry
season. Obviously the wet-season peaks must be lowered to prevent
flooding and to minimize fill requirements if development is to be
economically feasible in many areas. But if gated controls could be
installed on canals in areas of low water levels-such as near coastal
areas-the wet-season peaks would still be lowered, but the in-
creased water levels during the dry season would increase aquifer
storage, thereby providing a larger ground-water supply when de-
mand is greatest.
HYDRAULIC PROPERTIES
Several determinations of hydraulic properties of the shallow
aquifer in the Naples well field area have been made since 1952. In
the original well field in the southern part of the city, the average
transmissivity was 98,000 gpd (gallons per day) per foot, and the






BUREAU OF GEOLOGY


average storage coefficient was 0.0006 (Klein, 1954). In the south-
ern part of the existing well field the transmissivity is 185,000 gpd
per foot, and the storage coefficient is 0.0004 (Sherwood, 1961).
Both storage coefficients are very low and reflect an artesian rather
than a water-table condition: discontinuous overlying beds of low
permeability cause the shallow aquifer to react to short-term
stresses as an artesian aquifer.
The specific capacity of a well is the number of gallons of water
produced per foot of drawdown when the well is pumped at a
certain rate for a specific time. Using a method developed by Hurr
(1966), transmissivities ranging from 500,000 to over 800,000 gal-
lons per day per foot were obtained from specific capacities of test
wells along the Alligator Alley and east of Naples. These data indi-
cate that the permeability of the shallow aquifer in this area is
several times that in the Naples well-field area.
The downstream pick up in flow in the Golden Gate Canal sys-
tem during two periods in 1969 (see Surface Flow System section)
indicated hydraulic connection between the aquifer and the canal.
To confirm this connection, five wells (see fig. 9) on the west side
of SR 951 (Henderson Creek Road) and about 100 feet from Hender-
son Creek Canal were pumped November 1, 1970. The specific con-
ductance of the water pumped was determined at the beginning and
end of each pumping test. The specific conductance of water from
Henderson Creek Canal-sampled opposite the well being pumped-
was determined only at the end of each pumping test. The results
of those tests are listed below:
CONDUCTANCE
(micromhos
at 770F)

TIME HENDERSON
WELL NO. DEPTH DRAWDOWN DISCHARGE BEGIN END CREEK CANAL
(feet) (feet) (gpm)
C-450 31.7 0.22 250+ 1000 900 785
C-449 31.5 0.49 200 1600 1350 845
C-448 23.5 5.81 200 850 820 815
C-447 22.3 4.57 200 1220 1170 1100
C-446 24.7 3.80 200 790 840 1000
The table indicates hydraulic connection between the aquifer
and the Henderson Creek Canal in that where the canal water is
fresher than the ground water, the water from the well freshens
with pumping; where the canal water is less fresh, the water from
the well increases in salinity with pumping.






REPORT OF INVESTIGATION NO. 63


FLORIDAN AQUIFER
In recent years waste water has been injected into the lower
part of the Floridan aquifer at several locations in southeast Flor-
ida. At two locations, treated sewage is being injected and at a
third, industrial water. The industrial well and one sewage disposal
well are finished in the "boulder zone" of the aquifer, 2,000 to 3,000
feet below msl; the other sewage well is slightly more than 1,000
feet deep.
The suggestion has been made that the Floridan aquifer be used
also as a storage reservoir for surplus fresh water. During the wet
season, fresh water would be pumped into the aquifer though deep
wells, and during the dry season the fresh water would be recovered
for use.
The Floridan aquifer doubtless will become more important
when water demands are such that conversion of slightly saline
water to fresh water may become feasible.

WATER QUALITY
Along the coast in western Collier County, the quantity and
quality of water are of equal concern because without sufficient
quantity to maintain high fresh-water levels near the coast, salty
water from the gulf would contaminate ground water of good qual-
ity. Eastward expansion of the city of Naples well field is not prac-
tical because immediately east of the city mineralized ground water
occurs at relatively shallow depth in the shallow aquifer. However,
the shallow aquifer 15 miles east of Naples seems to contain large
quantities of ground water that is equal in quality to that of the
coastal area.
The quality of ground water is determined largely by the quality
of the rainfall, the materials through which the ground water
moves, and the length of time involved in the movement of the
ground water through the rocks and soil and down the streams.
Domestic and industrial wastes as well as sea water are sources of
mineral or biological contamination of streams and ground water.

NATURAL CONSTITUENTS
SURFACE WATER: Changes in water quality in the surface flow
system are greater and more frequent than they are in the aquifer.
This is due mainly to the system collecting unfiltered overland flow
and lack of filtering in the open channels. When no overland flow









TABLE 2,.-,CHIMICAL ANALYSES OF WATER FROM SELECTED CANALS IN WlESTERN COLLIER COUNTY,
(results in milligram per liter except where noted)


Station or
Site number


Date
of
Collection


Gordon River @
City Control
Structure

Golden Gate Canal
@ SR 858 Bridge


Gordon River @
U.S. 41, Bridge


Golden Gate
Canal Tributary


Cocohatchee River
Canal nr Naples,
Fla.
Henderson Creek
Canal nr Naples
Fahka Union Canal
nr Everglades City


10-26-70
2- 4.71
8.80-71
6.22-71
10-26-70
2. 4-71
8-80-71
6.22-71
10-26-70
2- 4-71
8-80-71
6.22-71
10-26-70
2- 4-71
8-80-71
6.22.71
65-19-70


906 7.4 27 26 10 8.4 0.06 0.02 110 18 1.0 68 2.4 260
1,700 7.7 10 20 6 1.4 .02 .01 110 81 1.8 190 8.8 264
82,900 7.6 21 80 7 2.6 .18 .04 880 590 6,500 280.0 204
84,000 7.6 27 50 25 5.8 .16 .11 870 790 6,700 2650.0 280


708 7.8 27
810 7.9 21
850 7.7 22
7900 7.9 27
88,400 7.6 80
40,000 7.6 19
47,000 7.7 28
84,000 7.8 80
688 7.5 29
680 7.7 20
640 7.6 20
660 7.7 28
500 8.0 22


5-19-70 1,200 8.2 29


40 15 18


.40 .02 120 5.0 .50
.04 .01 180 7.4 .66
.06 .01 120 9.0 -
.00 .00 120 11 --
.16 .02 840 760 4.2
.11 .04 840 500 10
.16 .08 880 580 -
.09 .02 820 810 -
.29 .01 120 4.4 .54
.12 .01 180 5.2 5.6
.16 .01 110 4.6 -
.16 .01 110 8.6 -
- 98 2.0 -


- 110 28 --


25 .8
86 1.2
47 1.4
60 1.5
6,600 260
8,100 810
11,000 380
6,700 250
20 .8
10 1.0
18 .8
18 .6


12 .8 268 26


120 4.5 824 84


56 180 0.2 0.02 0.05 218
87 880 .8 .08 .07 217
1,700 12,000 1.0 .48 .46 167
1,700 12,000 .9 .91 1.0 189
62 41 .2 .00 .08 259
70 64 .8 .02 .24 285
67 94 .2 .02 .05 289
68 120 .2 .05 .10 2658
2,000 12,000 1.0 .12 .14 177
2,100 14,000 1.5 .56 .57 161
2,400 18,000 1.4 .69 .76 185
2.000 12,000 .9 .54 .60 157
66 28 .8 .01 .01 264
62 24 .8 .02 .16 285
48 24 .2 .02 .05 256
48 26 .2 .04 .09 246


18 .4 .05 .05 220


210 .8 .08 .05 266


780 7.8 28 25 5.1 120 5.8 .80


0
4,


2-17-70


87 7 854 16 68 .2 290







TABLE 2. (CONTINUED)


Hardness Dissolved
as COCOs solids Nitrogen (N)



Station or oo o oo oo, .o



Gordon River i 880 120 578 510 0.05 0.04 0.002 0.01 0.000 0.01 0.8 0.2 0.1 0.00 0.00 0.1 0.09 0.70 -
City Control 400 190 955 940 .07 .08 .010 .01 .000 .01 .07 .08 .0 .01 .86 .0
Structure 8,800 8,100 21,500 .11 .07 .004 .05 .000 .02 .86 .80 .0 .01 .85 1
4,200 4,000 21,900 .09 .000 .08 .000 .04 .26 .89 .1 .08 :.0
Golden Gate Canal 820 62 478 420 .02 .08 .004 .01 .000 .00 .9 .2 .14 .00 .01 .1 .Of .50
@ SR 858 Bridge 860 71 502 490 .08 .05 .010 .00 .010 .01 .04 .08 .0 .02 .81 .0
840 97 668 490 .08 .06 .080 .00 0 .02 .09 10. .0 .01 .55 6.0
840 92 568 540 .07 .001 .01 .000 .02 .04 .08 .4 .08 6.0
Gordon River @ 4,000 8,800 22,100 .05 .04 .001 .02 .000 .01 40 .2 2.6 .40 .00 .0 .08 .62 -
U.S. 41 Bridge 2,900 2,800 25,000 .07 .09 .010 .08 .040 .00 ----.... .40 .49 .1 .04 ..94 .0
8,800 8,200 82,800 .16 .07 .008 .05 .000 .01 .20 1.1 .0 .08 .70 1.0
4,100 4,000 22,200 .07 .000 .04 .000 .01 -- .81 .26 .2 .08 5.0
Golden Gate 820 54 468 410 .08 .04 .002 .00 .000 .01 1.6 .2 .14 .10 .00 .0 .08 .62 .0
0anal Tributary 860 62 424 420 .08 .08 .010 .00 .050 .01 .08 .08 .0 .01 ..87 .0
290 88 486 860 .09 .11 .008 .00 .000 .01 .09 9.7 .2 .02 2.7 18.0
290 44 845 860 .01 .000 .00 .000 .01 .04 .08 .0 .02 4.0
Oocohatchee River 260 86 888 o00 -. .06 .0 .01 .80 -
Canal nr Naples,
Fla.
Henderson Creek 880 110 869 780 -- ... .08 .0 .07 .24 -
Canal nr Naples

Fahka Union Canal 880 44 466 480 .0 .01 -
nr Everglades City,








TABLE 3.-CIIEMICAL ANALYSES OF WATER FROM SELECTED WELLS IN WESTERN COLLIER COUNTY, g
(roeulta in milligrams per liter except where noted)


Hardness Dissolved

Station or Da % & sd
Bite number Collection




Naples well field 9.10.70 7,28 82 0.24 74 18 80 0,0 170 26 285
1BCE TH 1 6-28-.69 8.00 27 0.10 188 20 120 284 .24 887 117 912
TH 2 6-24-60 7.82 28 0.06 185 29 105 220 .18 842 114 00
TH 8 6-28.60 7.28 27 0.80 119 26 100 156 .8 840 66 7566
TH 4 6-25.69 7.18 28 0.25 119 22 50 122 .27 852 86 686
TH 5 6-24-69 7.98 27 0.20 144 18 89 162 .15 848 88 711
TH 6 6.25-69 7.85 25 0.10 160 26 66 274 .1 860 148 980
NA 7 6-18.70 7.85 81 0.04 95 9.5 8 80 .0 276 0 420
NA 8 6-80.70 7.70 16 0.04 82 15 16 86 .0 267 0 450
NA 9 7-14-70 7.75 88 0.04 96 18 10 86 .0 295 0 420
'USGS 7 6- 4-70 480 7.75 12 0.08 609 4.9 266 1 12 .75 218 245 8 277
8 6- 4-70 610 7.85 82 0.16 101 8.6 854 2 21 .95 290 802 18 878
9 6- 8-70 888 8.10 40 0.08 54 1.7 178 2 20 .85 142 189 9 202
10 6- 8-70 8.05 60 0.08 80 1.2 6 11 .15 77 4 187
11 60- 4.70 520 7.55 12 0.12 74 2.4 262 8 25 .96 215 286 14 810
11A 6- 8-70 700 7.75 20 0.04 85 14 842 27 28 1.0 281 298 81 486
0-802 7-24-659 625 7.6 2 25 0.01 72 16 89 4.6 886 11 82 .0 0.6 250 0 870
0-808 7-28.59 911 7.1 15 25 0.10 170 6.8 26 .2 620 4.4 46 .0 .8 450 24 599
0-804 8-10-69 609 8.1 15 10 0.01 70 15 40 4.6 808 14 41 .4 .2 240 0 865
0-805 8-12-59 1,040 7.6 18 0.00 100 17 88 1.9 290 16 180 .2 290 .8 820 87 688
0-450 11- 1-70 840 7.9 80 10 180 12 42 2.1 364 75 60 .8 299 .0 870 69 517 500
0-448 11- 1.70 770 8.0 0 8.5 110 9.8 48 1.6 878 5.2 72 .8 810 .0 820 11 449 440
0-446 11- 1.70 650 8.0 0 7.2 92 9.5 88 1.6 812 28 42 .2 266 .0 270 14 887 870

IBlack, Crow and Eidsness Inc. test holes and analyses. 'Analyses by Black, Crow and Eldeness, Inc.






REPORT OF INVESTIGATION NO. 63


occurs during the dry season, the canal flow is maintained chiefly by
inflow from the aquifer. Evapotranspiration of surface water during
the dry season causes chemical constituents to concentrate. Results
of analyses of water collected from selected sites in canals (fig. 5)
in western Collier County are shown in table 2. The chemical qual-
ity of the water is generally good except in the tidal reach of the
Gordon River. The increase in concentration of certain chemical
constituents upstream from the control in the Gordon River re-
sulted from sea water topping the control during high tides.
Surface water is seldom used in south Florida as a source of
municipal supply because fresh ground water is usually available in
large amounts and does not require expensive treatment that a sur-
face-water supply needs to make it potable. Marco Island obtains
water from a rock pit near the intersection of U.S. Highway 41 and
State Road 95 because the rock pit is the nearest source of a de-
pendable fresh-water supply.
Of the surface-water flow system of western Collier County, only
in the Golden Gate and the Fahka Union Canals is the flow large
enough to be considered a permanent source of water. However, dur-
ing the dry season, when water demands are greatest, the minimum
flow in Golden Gate Canal may be inadequate to meet future
demands.
GROUND WATER: Figure 9 shows the location of wells from which
water samples were collected for chemical analyses. Table 3 is a
compilation of those analyses. Several of the analyses were made by
Black, Crow, and Eidsness as part of a cooperative effort with the
county and the Geological Survey. Also included in the table is a
representative analysis of ground water from the Naples well field.
A comparison of the data in tables 2 and 3 reveals that in some
areas ground water is superior in quality to canal water. Also, both
the coastal and inland ground water is superior in quality to the
ground water immediately east of Naples. The area east of SR 951
is a potential source of ground water of good quality.

CONTAMINANTS
Contamination of water in western Collier County can be nat-
ural, man-made, or both. Salt-water intrusion into the aquifer and
canals is the most common type of natural contamination in coastal
regions; introduction of sewage and industrial wastes into canals
or the aquifer constitutes man-made contamination. Because of its
proximity, the gulf, is an ever-present source of natural contamina-





BUREAU OF GEOLOGY


tion; the free interchange of water between the surface flow system
and the aquifer increases the threat of man-made contamination.
NATURAL: Salt-water intrusion occurs when fresh-water levels
in the aquifer are not of sufficient height above msl to prevent the
inland movement of the heavier salt water; lowering water levels,
either by pumpage or drainage, upsets the natural balance between
fresh water and sea water.
The capacity of the well field (1971) in Naples is limited by the
threat of salt-water intrusion. Consultants for the city have calcu-
lated that withdrawals exceeding 20 mgd along the coastal ridge
would lower the water level in the aquifer between the well field
and the gulf to the point where salt-water intrusion would be
imminent.
The area 15 miles east of Naples, where the aquifer contains
water of good quality, would not be threatened by salt-water intru-
sion because of the distance inland from the gulf.
Another source of natural contamination is residual mineralized
water in the shallow aquifer immediately east of the Naples well
field. During the drought of 1970-71, the quality of water in the
Naples well field deteriorated because this mineralized water migra-
ted into the area of influence of the municipal water-supply wells.
The area 15 miles inland would probably not be affected by water
from this area of inferior water quality, but further exploratory
drilling is needed to determine the eastward extent of the area of
mineralized water.
MAN-MADE: Man-related contaminants that affect water re-
sources have been categorized by the FWQA (1969) into eight
general types: sewage and other oxygen-demanding wastes; disease-
causing agents; plant nutrients; synthetic organic chemicals; inor-
ganic chemicals and other mineral substances; sediment; radioactive
substances; and heat.
Preliminary data collected from a current supplementary U.S.
G.S. study in Collier County indicate man-made contaminants in the
water resources of western Collier County are well within the safe
limits established by federal water regulatory agencies.

WATER USE
Naples and the unincorporated areas of Golden Gate Estates and
Marco Island maintain the only public water supplies in western
Coier County. In 1970 the Naples well field pumped, on the aver-






REPORT OF INVESTIGATION NO. 63


age, 4.4 mgd and Marco Island, slightly less than 1 mgd. It is esti-
mated the Golden Gate Estates well field pumped less than 0.5 mgd
during 1970.
Acreage for agriculture in the investigation area varies yearly
but probably averages approximately 5,000 acres. Average irriga-
tion requirements for all crops are 1.5 to 2 feet per acre, or 6.5 to 10
mgd for the 5,000 acres. In western Collier County most of the crops
are irrigated with ground water pumped into conveyance canals
and ditches. Probably at least half the ground water pumped is
consumed.
Most industrial water is obtained from municipal wells that tap
the shallow aquifer. Also, private domestic supplies and lawn sprin-
kling systems plus self-supplied industries probably account for at
least 1 mgd from the shallow aquifer. The combined demand ap-
proximated 15 mgd in 1970. Canal discharge from the surface-flow
system in 1970 averaged about 350 mgd.
Consulting engineers for the city of Naples forecast that the
maximum daily rate of pumpage at the municipal water treatment
plant will exceed 20 mg by 1979. The 1970 maximum daily rate was
about 8 mg. The 1979 estimate probably exceeds the amount that
can safely be withdrawn from the aquifer by present well-field
facilities. Therefore, additional supplies from another source will be
needed at that time.
Analyses of data from both drilling of test wells and sampling
of surface water and ground water indicate that ground water in
quantities adequate to serve the future needs of western Collier
County can be developed from an area centered about 15 miles east
of the Naples city limits along Alligator Alley. Future drilling and
chemical analyses will delineate the limits of the source more
closely, but available data indicate water of good quality is available
for development in the aquifer underlying about a 100-square-mile
area.


SUMMARY AND CONCLUSIONS

Western Collier County has large fresh-water-supply potential
because of its 54 inches of rainfall annually and its manmade sur-
face flow system, hydraulically connected to a shallow permeable
aquifer. However, water problems exist because the rainfall is not
evenly distributed throughout the year, causing salt-water intru-






BUREAU OF GEOLOGY


sion to threaten the Naples well field during prolonged dry seasons.
Contamination of existing and future ground water supplies is
possible by man-related activities and urbanization.
The controlled surface-water flow system and the distribution
of weirs allow for water control without an excessive lowering of
ground-water levels. The system also has the potential for recharg-
ing the coastal section of the shallow aquifer during the dry sea-
sons. Variable water quality and inadequate flows during the dry
season precludes the use of the surface-water flow system as a
direct source of municipal water.
Water of good quality is contained in the shallow aquifer along
the west coast and for about 2 miles inland. The quality then de-
creases for about 10 miles inland. East of this area of ground water
of poor quality, thick sections of permeable limestone extend from
near land surface to a depth of almost 100 feet near SR 951 and
from land surface to more than 70 feet near Alligator Alley and SR
29. Quality of the ground water in this area is equal or better than
that in the coastal area; the quantity is much greater-perhaps sev-
eral times that of Naples coastal area.
More data collected in western Collier County are necessary to
more accurately determine the effects of the surface-water flow sys-
tem on the shallow aquifer in order for water managers to plan for
future water-resources development. In addition, a water-quality
monitoring network would be necessary to detect water-quality
changes in the surface-ground-water flow system as a result of con-
taminants by man-related activities.



WELL LOGS

WELL C-130
Depth, feet below
Material land surface
Sand, quartz, white in upper part, brown-rust in lower part.. 0-21
Marl, sheily, tan-gray, clayey, sandy; few rock fragments. .. 21-26
Limestone, soft, marly, very shelly ...................... 26-36
Marl, sandy, shelly, brown phosphate material............. 36-44
Limestone, gray to cream, very shelly, marl............... 44-51
Marl, tan-cream, sandy, shelly.......................... 51-58
Marl, white to light gray, very shelly and sandy, some
Hmestone fragments ............................... 58-63
Limestone, white to gray, shelly, cavernous, sandy. ........ 63- 71





REPORT OF INVESTIGATION NO. 63


WELL C-174
Depth, feet below
Material land surface
Sand, quartz, medium, gray ............................ 0- 2
Limestone, tan, hard .................................. 2- 10
Limestone, tan, shelly, softer than above.................. 10- 20
Limestone, white .................................... 20- 25
Limestone, mostly shell, loosely cemented; thin beds of marl.. 25- 41
Limestone, white to gray, very shelly .................... 41- 50
Limestone, white to gray, permeable..................... 50- 78
Limestone, white, sandy ............................... 78- 88
Sandstone, calcareous, sand increasing at bottom........... 88 -140



WELL C-185
Depth, feet below
Material land surface
Sand, quartz ........................................ 0- 9
Marl, dark, hard ..................................... 9- 13
Sand, quartz, fine to medium, marly, very shelly........... 13- 25
Limestone, white to dark gray, shelly, sandy, permeable ..... 25- 92
Sand, quartz, very fine, gray to tan...................... 92-115
Sand, quartz, very fine to medium, tan to green, phosphatic... 115 141



WELL 7
Depth, feet below
Material land surface
Fill and marl........................................ 0- 5
Limestone, some shell ................................. 5-45
Sand, quartz, clean .................................... 45-50


WELL 8


Material


Fill ........................ ........ ...............
Limestone, dark gray, permeable, shelly..................


WELL 9


Material


Limestone, low permeability, very hard. ..................
Limestone, alternating hard, low permeability
layers with soft permeable layers, shelly...............
Sand, brown, "dirty" ..................................


Depth, feet below
land surface


0- 4
4-85


Depth, feet below
land surface


0-17

17-60
60-75





32 BUREAU OF GEOLOGY


WELL 10
Depth, feet below
Material land surface
Fill brown ......................................... 0- 5
Limestone, large shells, permeable ...................... 5-32
Limestone, tan, very permeable, sulfur odor ............... 32-62
Limestone, shelly .................................... 62-70
Sand .............................................. 70-82

WELL 11
Depth, feet below
Material land surface
ill ............................................... 0- 5
Limestone, varying hardness, permeable, shelly............ 5-67

REFERENCES

Davis, J. H., 1943, The natural features of southern Florida, especially the
vegetation and the Everglades: Fla. Geol. Survey Bull. No. 25.
Federal Water Quality Administration, 1969, Summary and status of water
quality standards for interstate waters of Florida.
Hem, J. D, 1959, Study and interpretation of the chemical characteristics of
natural water: U.S. Geol. Survey Water Supply Paper 1473.
Hurr, R- T, 1966, A new approach for estimating Transmissibility from speci-
fic capacity: Water Resources Research vol. 2, no. 4, p. 657-664.
Klein, Howard, 1954, Ground-water resources of the Naples area, Collier
County, Florida: Fla. Geol. Survey Rept. of Inv. No. 11.
Klein, Howard, and others, 1970, Some hydrologic and biologic aspects of the
Big Cypress Swamp drainage area, southern Florida: U.S. Geo. Survey
Open-file Report.
Little, J. A., Schneider, R. F., and Carroll, B. J., 1970. A synoptic survey of
livnological characteristics of the Big Cypress Swamp, Florida: Federal
Water Quality Admin.
McCoy, H. J., 1962, Ground-water resources of Collier County, Florida: Fla.
GeoL Survey Rept. of Inv. No. 31.
Sherwood, C. B. and Klein, Howard, 1961, Ground-water resources of north-
western Collier County, Florida: Fla. Geol. Survey Inf. Circ. 29.




Full Text
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STATE OF FLORIDA DEPARTMENT OF NATURAL RESOURCES Randolph Hodges, Executive Director DIVISION OF INTERIOR RESOURCES Robert O. Vernon, Director BUREAU OF GEOLOGY Charles W. Hendry, Jr., Chief Report of Investigations No. 63 HYDROLOGY OF WESTERN COLLIER COUNTY, FLORIDA By JACK McCoY Prepared by U.S. GEOLOGICAL SURVEY in cooperation with COLLIER COUNTY CITY OF NAPLES BUREAU OF GEOLOGY FLORIDA DEPARTMENT OF NATURAL RESOURCES TALLAHASSEE, FLORIDA 1972

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CONTENTS Page -Abstract ---------------------------1 Introduction 1----------------------1 Purpose and scope of investigation -------------------1 Previous investigations -------------------------3 Acknowledgments ------------------------------3 General features -------------------------------4 Climate ----------------------------------6 Physiography and drainage -----------------------6 Water problems --------------------------------7 Hydrology ----------------------------------9 Surface flow system -------------------------------9 Shallow aquifer ------------------------------14 Recharge and discharge -------------------------16 Hydraulic properties -------------------------------------21 Floridan aquifer ------------------------------------------23 Water quality -------------------------------23 Natural constituents ----------------23 Surface water ------------------23 Ground water -----------------------------27 Contaminants ----------27 Natural ---------------------------28 Man-made ------------------------------28 Water use ------------------------------------Summary and conclusions ---------------------------29 Well logs -------------------------------30 References ------------------------------32

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ILLUSTRATIONS Figure Page I Map of Florida showing location of Collier County -----2 2 Location of area of investigation ----------------4 3 Physiographic regions of Collier County (after Davis, 1943, figure 1) 7 4 Map of the Big Cypress Watershed showing flow directions in December, 1969 (after Klein and others, 1970, figure 3)---------------8 5 Canal system in western Collier County showing location of weirs and discharge stations -----------------------10 6 Hydrographs of discharge for selected canals in western Collier County ----------------------------------------12 7 Direction and amount of flow in the Golden Gate Canal system on May 13 and July 22, 1969 ----------------------------13 8 Generalized geologic section along line A-A' in figure 9 --------15 9 Location of test holes and line of generalized geologic section-------17 10 Location of wells equipped with water-level recorders -------------19 11 Hydrographs of selected wells in western Collier County and rainfall at Naples ---------------------------------------20

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TABLES Table Page 1 Average monthly and 1970 monthly temperatures and rainfall at Naples 5 2 Chemical analyses of water from selected canals in western Collier County --------------------------------------26 3 Chemical analyses of water from selected wells in western Collier County ----------------------------------24

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HYDROLOGY OF WESTERN COLLIER COUNTY, FLORIDA By Jack McCoy ABSTRACT Although the fresh-water-supply potential of western Collier County is large, water problems exist in that the 54 inches of annual rainfall are not evenly distributed throughout the year, salt-water intrustion threatens the Naples well field during prolonged dry periods, and contamination of existing and future ground-water supplies is possible by man-related activities. The controlled surface-water flow system of the GAC (Gulf American Corporatioh) developments minimizes the threats of floods without an excessive lowering of water levels near the coast. Variable water quality and inadequate flows during the dry season preclude the use of the surface-water flow system as a direct source of municipal water. Naples well-field expansion is limited by water of inferior quality in the shallow aquifer immediately east of the well field. The shallow aquifer in an area starting about 11 miles inland and extending eastward to State Road 29 contains water of good quality. The shallow aquifer extends from land surface to a depth of almost 100 feet near SR 84 and SR 951 and from land surface to more than 70 feet near SR 84 and SR 29. Available data indicate the aquifer in this area has a capacity several times that in the Naples coastal area. INTRODUCTION PURPOSE AND SCOPE OF INVESTIGATION Collier County, in southwestern Florida (fig. 1), receives abundant rainfall, 54 inches annually. The western third of the county is underlain by permeable sediments about 100 feet thick containing water of good quality in most places. However, water problems exist in the county. The major problem is the development of additional fresh water supplies to meet the demands of the rapidly growing population. The projected rapid growth rate prompted officials to take action not only by expanding municipal water-supply systems but also by suggesting that investigations be made to establish 1

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2 BUREAU OF GEOLOGY A L A 8 A M A V w-a ,a j -Jacs G E 0 R G I A * -(ASSAUICT --R --i -,r -T" io.! uTNAM A f .i o. C ' -ASCO -1...--L SA*TtC I H DEE | C Oc V 1 -"--. HIGHLlDS o .,. , , , 0,_ S25 50) 75 MILES RoTTE LEE NDRY " .AL BEACH LOCATION OF AREA II NiOE l Af E Figure 1.-Map of Florida showing location of Collier County.

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REPORT OF INVESTIGATION NO. 63 3 possible new well-field sites in inland areas. The U.S. Geological Survey was requested in 1967 to locate areas that would most likely yield the greatest quantities of the best quality water to satisfy the projected municipal needs of western Collier County. The investigation included the following phases: (1) evaluation of existing data; (2) determination of the hydrologic and geologic characteristics of the subsurface materials; (3) collection of miscellaneous discharge data in the inland canal complex and interpretation of the data; and (4) determination of the quality of water. This report was prepared by the U.S. Geological Survey in cooperation with Collier County, the city of Naples, and the Bureau of Geology, Florida Department of Natural Resources. The work was under the immediate supervision of T. J. Buchanan, Subdistrict Chief, Miami, Florida, and under the general supervision of C. S. Conover, District Chief, Tallahassee, Florida, both of the U.S. Geological Survey, PREVIOUS INVESTIGATIONS Two reports, "Ground-water resources of the Naples area, Collier County, Florida, 1954", by Klein and "Ground-water resources of northwest Collier County, Florida, 1961", by Sherwood and Klein, summarize the geologic and hydrologic conditions in northwestern Collier County. The report "Ground-water resources of Collier County, Florida, 1962", by McCoy gives a general portrayal of the geologic and hydrologic conditions throughout the county. Some hydrologic and biologic aspects of the Big Cypress Swamp watershed are described in a preliminary report by Klein and others (1970). Day-to-day variations in physical, biological (including bacterial), and chemical character of the water flowing into, through, and discharging from the Big Cypress Swamp watershed during March 1970 are recorded in the report by Little and others (1970). ACKNOWLEDGMENTS Many public officials have contributed valuable information and assistance during the study. Among them were W. H. Turner, County Manager; Tom Peeke, County Engineer; and W. F. Savidge, Director of the Naples Public Works Department. Dr. J. I. GarciaBengochea and Robert Ghiotto of Black, Crow, and Eidsness, Inc. rendered many services and courtesies.

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4 BUREAU OF GEOLOGY GENERAL FEATURES Collier County consists of 2,119 square miles in the southwestern part of Florida, making it the second largest county in the State. The county is bounded on the west and southwest by the Gulf of Mexico, on the north by Lee and Hendry Counties, on the east by Broward and Dade Counties, and on the southeast by Monroe 45' 30' 15' 8100 ^ "» _ .HENDRY COUNTY i I I 7 -L iC L COUNY STUDY AREA SNA ONAL i oi I iro --I ) Lgcou~~ ~----------'. S L, 0 .M i .es I Figure 2.-oLocation of area of investgaton. 0C,. NATIONAL ! 9 10 MUiles Figure 2.-Location of area of investigation.

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REPORT OF INVESTIGATION NO. 63 5 TABLE 1.-AVERAGE MONTHLY AND 1970 MONTHLY TEMPERATURES AT NAPLESi Temperature (*F) Rainfall (inches) 1942-1970 1970 1942-1970 1970 January 65.5 60.7 1.74 1.95 February 66.5 61.7 1.76 1.97 March 71.0 68.5 2.39 13.56 April 73.6 75.4 2.01 May 77.1 75.9 3.98 5.32 June 80.9 80.4 8.16 6.48 July 82.4 82.0 8.30 5.26 August 82.9 82.7 8.19 4.68 September 81.9 81.7 9.55 13.32 October 77.1 77.5 4.96 2.87 November 71.1 67.1 1.39 .43 December 66.6 65.7 1.25 .02 Average 74.6 73.3 54.65 55.86 iU.S. Weather Bureau, Climatological Data, 1942-1970. County. The principal municipalities are Naples, on the west coast, Immokalee in the north-central part, and Everglades City, on the south coast. The area of investigation consists of about 280 square miles in the western quarter of the county (fig. 2). The area's boundaries are roughly the Naples city limits on the west, State Road 846 on the north, the Fakha Union Canal on the east, and U.S. Highway 41 (Tamiami Trail) on the south. About half the area has been platted for single and multiple-unit dwellings by GAC (Gulf American Corporation). Streets in nearly one-third of the platted segment have been completed. A massive canal system has been established by the developers to provide flood control. Weirs that have been placed throughout the canal system to control the flow prevent excessive drainage. Collier County was the fastest growing county in Florida during 1960-70, increasing in population from almost 16,000 to slightly more than 38,000. In 1970, Naples and its environs accounted for about two-thirds of the population, and the population in the area of investigation was about 1,000, mostly residents of the Golden Gate Estates development. Projected population for Golden Gate Estates exceeds 50,000. Agriculture is the principal industry in the area investigated. Several thousand acres of Golden Gate property in the northern part of the development is leased for growing cucumbers, water-

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6 BUREAU OF GEOLOGY melons, tomatoes, and peppers. Farming on a smaller scale is active along US. Highway 41 also. CLIMATE Climate in Collier County is humid subtropical: summers are warm and wet, and the winters are mild and dry. Total rainfall in Naples for 1949-70 averaged 54 inches (table 1). Most of the rainfall occurs during June through October. The summer rains are usually tropical, frequent, intense, and of short duration. Winter rains are associated with weather fronts and are usually longer but less intense, and they vary widely in frequency. Because of the cooling effect of summer rains, the highest daily temperature during the summer is about 950F. The lowest daily temperature for the winter is about 340F. Cold periods usually follow the frontal rains and do not last more than a few days at a time. The average annual temperature in Naples is about 75°F (table 1), the summer average is 820F, and the winter average is 660F. PHYSIOGRAPHY AND DRAINAGE Davis (1943, fig. 1) divided Collier County into three physiographic regions: The Flatlands, the Big Cypress Swamp, and the Southwest Coast and Ten Thousand Islands (fig. 3). Most of the investigation area lies within the Big Cypress Swamp region and is characterized by swamps containing large cypress trees, islands of pine forests, and wet marl prairies. Most of this region is less than 15 feet above msl (mean sea level). The southern part of the area lies within the Southwest Coast and Ten Thousand Island region and contains tidal streams, bays, lagoons, and thousands of shoal-water islands. The area south of U.S. Highway 41 is primarily mangrove swamps and salt-water marshes. Drainage in Collier County is determined by topographic configuration and canals. Because of the flat topography and slow natural drainage, no well-defined stream system is developed except for the Gulf Coast estuaries, where drainage is through tidal channels. In the fresh-water environment, most drainage is through sloughs and strands and by canals, as shown in figure 4. Drainage in the area investigated is characterized by an extensive system of controlled canals, which drain southward and westward into the Gulf Coast estuaries (fig. 2). Outlets for the system are the Golden Gate Canal at Naples and the Fahka Union Canal

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REPORT OF INVESTIGATION NO. 63 7 N F LA TLA N D-S 0. P Figure 3.-Physiographic regions of Collier County, Florida (after Davis, 1943, figure 1). northwest of Everglades City. Part of the area southwest of Immokalee is drained to the gulf north of Naples by the Cocohatchee River Canal. The Henderson Creek Canal, southeast of Naples, drains the southwestern part of the area investigated. WATER PROBLEMS In western Collier County, as in most of southern Florida, the major water problems are: 1) Availability and protection of potable ground-water supplies in vicinity of population centers. 2) Quality of water in areas of potential well-field expansion. 3) Protection of ground-water supplies from excessive drain-

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8 BUREAU OF GEOLOGY i \iI S I COLLIER COUNTY Lake Tarfford z \\ ' i / EVERLADEES NATLIEA COUNTY -Tge M o th Cy th ho o t December, 1969 (after Klein and others, 1970, figure 3). 4) threat of contamination of potable ground-water supplies oo 1 I0 ". Nearly all ground water for public use in western Couier County PI I is supplied by the city of Naplyes well field. The well field is less than 2 miles inland from the gulf and has always been threatened by salt-water intrusion. Production of treated ground water from the l a gCokolcugse COWER n COUlle Cont / y by man-made chemicals and wastes. is supplied by the city of Naples well field. The well field is less than 2 miles inland from the gulf and has always been threatened by salt-water intrusion. Production of treated ground water from the

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REPORT OF INVESTIGATION NO. 63 9 well field has increased from an average daily rate of 0.2 mgd (million gallons per day) in 1950 to 4.4 mgd in 1970 and is predicted to exceed 17 mgd by 1990. The withdrawal of 17 mgd without serious contamination resulting from salt-water intrusion will present a formidable problem for water managers. Expansion of the Naples well field to the north and to the south is extremely limited by natural salt-water contamination in the aquifer. For about 10 miles inland the quality of the ground water is inferior to the water in the existing well field. Therefore, development of additional ground-water supplies will have to start in an area at least 10 miles inland, a considerable distance from the majority of the water users. Urbanization in the inland areas required the construction of a large canal network to lower water levels in areas historically swampy and to prevent flooding. However, increased water needs resulting from the urbanization will require careful management of the canal network in order to avoid depleting ground-water supplies because of excessive drainage. The possibility of contaminating fresh-water supplies by manmade wastes and chemicals continues to increase as more land is developed. The method and degree of treatment and the location of waste-disposal sites will have a significant effect on the quality and the quantity of future water supplies. HYDROLOGY SURFACE FLOW SYSTEM Construction of the extensive canal system shown in figure 5 was begun in the early 1960's with the excavation of the Golden Gate Canal, the primary canal in the western part of the system. Excavation of the Fahka Union Canal, the .primary canal in the eastern part of the system, was begun in 1968. Several secondary canals connect with the Golden Gate Canal, whereas the Fahka Union Canal is the combination of four parallel primary canals. The canal systems provide controlled drainage to permit development of the Golden Gate Estates, east of Naples, and the Remuda Ranch Grants, southeast of Naples. Before construction of the canals, much of the area was inundated each year during the rainy season. The Golden Gate Canal extends about 20 miles inland from the Gordon River. The bottom of the canal is 5 feet below msl at its outlet to Gordon River and 6 to 8 feet above msl in the interior. The

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10 BUREAU OF GEOLOGY 81*45' 81130 fi! 0 1 2 3 4 MILES 1\ i L .I W-5I669 LEE COUNTYj " ^--W , 46-70 COCOHATcHEF RIVER CANAL I ---_------.. _ '?"" ii \ I iL -i --J^.^ I 1 GOD EN GATE BLVD. _ _ _ _ ----___ -I-1 8-67 U) a IGO N I I I I I I I I SEMINOLE j_4 STATE GATE 9 --^ -. -\A-' r< ^^ -s==:^?<6 --------FCgan 5.--Canals in western Collier County showing location of weirs and isct disharge stations.snin Figure alwester n Collier County showing location of weirs andER discharge stations.

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REPORT OF INVESTIGATION NO. 63 11 design plans for the Fahka Union Canal call for similar bottom elevations. Distributed throughout the canal system are about 30 weirs, which increase in elevation toward the interior. The elevations of the coastal weirs on the Golden Gate and Fahka Union Canals (numbers 8 and 24) are 3 and 2 feet above msl. The elevation of the highest interior weir (number 13 near Immokalee) is 17 feet above msl. The function of the canals is to lower annual peak water levels to prevent flooding during the rainy season. The function of the weirs is to control the canal flow and reduce the possibilities of overdrainage. During the rainy season, when water levels in the interior are high, water moves from aquifer storage into the canals and downstream over the weirs. At the beginning of the dry season, flow over the inlandmost weirs ceases but continues over the downstream weirs. Flow over the weirs ceases in succession downstream, as the dry season continues, until flow occurs only at coastal weirs on the primary canals. Water has continued to flow over the coastal weirs in both primary canals since the canals were completed. The shallow depth of the canals and the distribution of weirs at selected elevations within the canal system limit drainage from the shallow aquifer in the inland areas. By limiting drainage from aquifer storage, regional water levels near the coast are not lowered excessively, and, therefore, the problem of sea-water intrusion is not magnified. Continuous records of discharge are obtained at all outlets of the canal system (fig. 5). Flow in the Golden Gate Canal is measured upstream from weir W8. The record began October 1964. Flow in Fahka Union Canal is measured upstream from weir W24, beginning in December 1969, and in the Henderson Creek Canal, about 4 miles south of Alligator Alley, (SR84), beginning in August 1968. Flow in the Cocohatchee River Canal was originally measured near a bridge on SR846 about 1 mile east of U.S. Highway 41, but channel improvements produced tidal effects at the gaging site, and the station was relocated to its present site in October, 1968. Hydrographs of these four canals for the periods of record are shown in figure 6. The Golden Gate Canal is about 100 feet wide, less than 8 feet deep, and has several fixed weirs throughout its reach of about 26 miles; the Fahka Union Canal is similar in width and depth and about 30 miles long; the Henderson Creek and Cocohatchee River Canals are about 25 feet wide, less than 5 feet deep, and 7 and 13 miles in length, respectively. The Henderson Creek Canal is uncontrolled except for a constriction at Alligator Alley which acts as a surface-water divide most of the time. However, at the peak of the

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12 BUREAU OF GEOLOGY 3000 1 -1 2000 GOLDEN GATE CANAL 1000500 5030 1964 1965 1966 1967 1968 1969 1970 I*300 t. 200 HENDERSON CREEK -COHATCHEE REK FAHKA UNION 10 CANAL CANAL CANAL 0ooCANAL 50 5S1968 1969 1 1970 1968 1969 1970 1969 1970 Figure 6.-Hydrographs of discharge for selected canals in western Collier County. rainy season, the Henderson Creek Canal probably receives some flow from the Golden Gate Canal. The Cocohatchee River Canal has a control a short distance upstream from the gaging station. Farmers regulate the control according to irrigation needs. The Cocohatchee River Canal drains most of the area southwest of Lake Trafford, but it also helps drain the Golden Gate area during peak wet periods. Because of their larger channels and drainage basins, the Golden Gate and Fahka Union Canals discharge more water than the Cocohatchee River and Henderson Creek Canals. The discharge of all the canals responds quickly to rainfall on their respective drainage basins, as demonstrated by the response to rainfall in early June, 1969. (See rainfall graph in fig. 11). On the other hand, rainless periods produced sustained declines of all discharges such as those of April and most of May 1970. Only a trace of rainfall was recorded at Naples during April and the first three weeks of May. The rapid decline of the flows throughout this period suggests very little ground-water inflow. This could be due to either low permeability of the aquifer or shallowness of canals or both. The closeness of the water table to land surface throughout the area of investigation, the flatness of the drainage basins, and the

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REPORT OF INVESTIGATION NO. 63 13 S81*45 81-30' ,A SR \ \ 46 O I 2 3 4 MILES I \ I \ __ -LEE COUNTY_ j I \\ COCOHATCHEE RIVER CANAL * S I SR I S I I I I I I S\ 74 4....." 4" s 1158 rI .. -GATE m I 7 > G G OLDEN :. REMGUD RANC A N' I I I I SI i95i 14 PARK I I I IREMUDA IRANCH IGRANTS I I I ca 0-1 i i 19 69(. w er .EXPLANATION I Canal and Weir I SEMINOLE STATE F PARK Direction and amount of flow, in cubicfeet per secand,on 41 May 13(upper)and July22, MARCO 1969(lower). 8145' 81'30' Figure 7.-Direction and amount of flow in the Golden Gate Canal system on May 13 and July 22. 1969.

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14 BUREAU OF GEOLOGY intensity of most of the rainfall requires that drainage canals in developed areas be adequately designed to remove surplus rainfall quickly if flooding is to be prevented. The sharp rises of the discharge peaks in figure 6 indicate the rapid removal of flood waters; the short duration of the peaks and the rapid declines indicate that a minimal amount of water reaches the aquifer as recharge. During 1970 the average discharge at each of the four stations was: (1) Golden Gate Canal, 250 cfs (cubic feet per second); (2) Fahka Union Canal, 270 cfs; (3) Henderson Creek Canal, 25 cfs; and (4) Cocohatchee River Canal, 15 cfs. Near the end of the dry season in 1971, discharge at the Golden Gate Canal outlet reached a record low of less than 20 cfs (about twice the average daily pumpage of the Naples water system in 1970). Figure 7 shows the direction and amount of flow in the Golden Gate Canal system on May 13 and July 22, 1969. These periods were representative of flow conditions near the end of the dry season and near the beginning of the wet season, respectively. Weirs completed at the time of the measurements are identified by a symbol and number. The contrast in flow on the 2 days is readily apparent, except for the inlandmost part of the system. Also apparent is the downstream increase in flow on both days. On May 13 this increase resulted largely from prolonged ground water seepage into the canal from aquifer storage. Even during this driest part of the year, 91 efs, or about 60 mgd, was discharged into the tidal reach of the Gordon River. Flow at every measuring site on July 22 was almost 10 times that on May 13, except for the unfinished inland part of the system, the Cocohatchee River Canal, and the Henderson Creek Canal. SHALLOW AQUIFER All fresh ground water used in western Collier County for municipal, domestic and industrial supplies, and for irrigation is obtained from a shallow unconfined aquifer. The shallow aquifer is composed of the Pleistocene terrace sands, the permeable limestones and sands of the Pleistocene Anastasia Formation, and the upper permeable limestones of the late Miocene Tamiami Formation (McCoy, 1962, p. 24). The aquifer is underlain nearly everywhere by a thick section of sand or clayey limestone. The maximum thickness of the shallow aquifer is about 130 feet in Naples, where the terrace sands and the Anastasia and Tamiami Formations are all present

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I-I A A'llFAHK UNIONCA. This part of section is not _ shown in figure 9. T T :2 MEAN (5 SEA 2 2 ... ;.. .. LEVEL 4--0 25 e e25 S100 .1 SLimestone Sand Marl 100 125 -.Sandy Shelly Sandy, 125 SMiles LIMESTONE " "' '' ''1" '' " .''"m .^-, 1 50 Cd 125 -;. ,' ' ' Sany ghell S dy .125 J 9 ! ? , SMiles LIMESTONE leO5 S 180 ,'

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16 BUREAU OF GEOLOGY and have some hydraulic connection. Thickness of the aquifer varies for several miles inland from the coast. The aquifer is usually thickest at the coast, thinning to the northeast, east and southeast. Figure 8 is a generalized geologic section from Naples to SR 29 along line A-A' in figure 9. The figure shows the undulation of the bottom of the aquifer and the presence of sand and shelly marl in the upper 50 feet near the coast. The permeability of the aquifer varies considerably. The limestone and shell beds near the coast are permeable, and 8-inch wells drilled in them will yield 500 gpm (gallons per minute) with 7 to 15 feet of drawdown. In the area east and southeast of Naples to about SR 858 and SR 84, the aquifer is less permeable, and the water in it is more mineralized. Also a localized shallow dense limestone (not shown in figure 8) retards rainfall infiltration in much of the area immediately east of the Naples well field, thus inhibiting the flushing of residual sea water (sea water trapped in the sediments during deposition) from the aquifer in this area. Farther inland, where the subsurface materials are more continuous and homogeneous, the aquifer is more permeable than it is in the coastal area, particularly from test hole 11 (fig. 9) eastward to SR 29 and north to about Golden Gate Boulevard. RECHARGE AND DISCHARGE Infiltration of rainfall and seepage from controlled canals are the means of recharge to the shallow aquifer. Recharge from rainfall is greatest during the rainy season, June to November. Recharge from canals is greatest during the dry season, December to May, when canal levels immediately upstream from the weirs are higher than adjacent ground-water levels. Discharge from the aquifer is by evapotranspiration, by groundwater flow to canals and the gulf, and by pumping from wells. Groundwater and surface-water flow and losses by evapotranspiration are greatest during and shortly after periods of rainfall, when water levels in the aquifer are high; discharge by pumping is greatest during dry periods, although it constitutes only a small part of the total discharge from the area. Changes in aquifer storage are indicated by fluctuations of the water table. When recharge to the aquifer is greater than discharge-which is usually only during a rain-the water table rises; when discharge from the aquifer is greater than recharge-which is most of the time-the water table declines. Fluctuations of the

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REPORT OF INVESTIGATION NO. 63 17 81145' 81l30' A SR 0 1 2 3 4 MILES t .'i I.\\ Ijl I I \\ S LEE COUNTY J COCOHATCHEE RIVER CANAL I I 1i ,H I,.2 T._3 ...304 1 S C-3 1 '18 581 T H4 *L -Ci GOLDEN GATE BLVD. I I I I 0411 j GATE " ) a NA I -oI -I ,A G'OLDEN,_, A! Cn--adW GATE ei STT e allseanlllllnel ISLADI C--130 .. .... 45p 12 181 4n9 9 NAPLES -44 A(C-185 951 13. 1 c-305 C -44 a of C'447 h 41 A L , = -446 I i I I I 0 I I I -EXPLANATION r_ ..Canal andWeir /OLLIER SSTATE F U.S.G.S.test hole PARK County test hole -i1 Geologic sectionline I.SLAND 1 v -0 ^ 'y / ^ 1 81045' 81-30' Figure 9.-Location of test-holes-and line of generalized geologic section.

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18 BUREAU OF GEOLOGY water table are monitored by automatic recording instruments on five wells shown in figure 10. Hydrographs of these wells for their periods of record are shown in figure 11. Monthly rainfall at Naples is included for comparison. Ground-water-level data are not available for the area east of Naples before the canals were constructed because the area was flooded or swampy through most of the year, and access was very difficult. Local lowering of levels began with the construction of the Cocohatchee River and Henderson Creek Canals, and regional lowering followed construction of the Golden Gate Canal and finally the Fahka Union Canal. The hydrographs in figure 11 began too late to reflect the lowering of -vater levels when canal construction started but show the changes that occurred as construction continued. Predrainage levels were above land surface much of the year, which would indicate the canal system lowered ground-water levels 1 to 2 feet before the weirs were installed. Wells C-384 and C-381 are located, respectively, adjacent to the Cocohatchee River and Henderson Creek Canals near their outlets. The hydrographs of the two wells (fig. 11), plus early periodic measurements in well C-384 show that water levels in the two wells were higher in the rainy season of 1965 than in the two previous years, even though the 1965 rainfall was below average. This suggests that the completion of weir W-4 and W-8 in October 1964 may have caused the Cocohatchee River and Henderson Creek Canals to act as relief outlets for the Golden Gate Canal system during the wet seasons. However, as the Golden Gate Canal system was extended inland, surface water that normally drained to the Cocohatchee River Canal was diverted to the Golden Gate Canal system. This is indicated by the lowering, in 1970, of the peak levels in C-384 and the decrease in discharge of Cocohatchee River Canal. For the same period the area around C-381 was flooded most of the time, and the discharge of Henderson Creek Canal increased. Wells C-383 and C-382 are within the influence of the Golden Gate Canal system (fig. 10); but C-383 is adjacent to a narrow borrow ditch, and C-382 is in the urbanized section of Golden Gate Estates and about three-quarters of a mile from the Golden Gate Canal Since 1965, wet-season water levels in well C-383 appear to have risen about a foot; since mid-1967 the dry-season levels have risen about a foot also. These effects are probably the result of a combination of (1) improvements in the canal system, which allow the borrow canal to convey more water during the wet season, (2) the installation of weir 10 immediately downstream from C-383, and

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REPORT OF INVESTIGATION NO. 63 19 81*45 81-30' 0 I 3 4 MILES / I _ _ , \\ LEE COUNTY \ -27 '"I 11 i S\ .CO'COHATCHEE RIVER CANAL -I 1 0^ ~----------------------*--~d ' -REUDI RN I G'NS GOLDEN GATE BLVD. i i " i r .... -.' ----eOLDEN Ier GO L I GATE .__ " """-'r'""""" i"-i> GOLDEP 1 "% 3----------------, ,, NAPLES I I I • 41 , SiREMUDA iRANCH iGRANTS ! -EXPLANATION -..1 P Conol and Weir COLLIER 5 I -381 SEMINOLE ji 85 wCSTAT Observation wel 1 a f well equ PARK w I recrd number) equipped with PARK water-level recorder. \ ISLAND 0 i 81645' 81a30' Figure 10.-Location of wells equipped with water-level recorders.

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20 BUREAU OF GEOLOGY -' I I -I LAND SbRFACE 12 WELL C-271 t ItI I I I l S2 I 1 I LAND SURFACE w ,c WELL C-384 < -t t I .I I 1. ...I . U I I ' LAND S URFACE ' WELL C-383 10 I W I J .11 -I -; 6 S I I LAND SURFACEI I I 10 196 1 1963 -? 1964 1... 196 9 19 67 19 19 I I[ {i -RAINFALL -; F si I -d ---Annual i r C-r-----l -Z m l WE in C-382r Zy I" ----Monthly r -t L L-pz r -I 1 RAINFALL 2 19I1 [ 1962 I 1963 11964 [ 1965 1966 1967 1968 | I 1970 Figure 11.-Hydrographs of selected wells in western Collier County and monthly rainfall at Naples. monthly rainfall at Naples.

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REPORT OF INVESTIGATION NO. 63 21 (3) the above-average rainfall starting in 1967 after 4 years of below-average rainfall. The hydrograph for well C-382 shows a generally consistent pattern for 1963-68. Except for short-term fluctuations due to abnormally high or low monthly rainfall, the seasonal water levels are generally similar. The slight rise in levels starting in 1969 is probably the result of above-average rainfall. Well C-271 is near the inlandmost reach of the Golden Gate Canal. The hydrograph for the well shows little year-to-year variation before 1966. Completion of the Golden Gate Canal into the area near the well has doubtless caused the decline in seasonal water levels in 1967-69. Completion of the weir installations and aboveaverage rainfall in early 1970 are probably responsible for the higher dry-season levels in 1969-70. Water levels in well C-271 during the last half of 1969 and all of 1970 indicate most graphically the effects of the canal system on the water levels in the shallow aquifer. If the trend of the last 18 months in the hydrograph for C-271 persists, the canal system will have been effective in lowering wet-season levels as much as 1.5 feet and dry-season levels about 1 foot below pre-construction levels. In summary, the effects of the canal system on the shallow aquifer can be only approximately evaluated at this time (1971) because the data-gathering period since completion of weir installations is too short for detailed analysis. If trends indicated in 1969 and 1970 persist, the canal system may lower wet-season water levels at least 2 feet and perhaps as much as 4 feet in the far interior areas. The hydrographs in figure 11 show the water level in the shallow aquifer fluctuates as much as 6 feet from wet season to dry season. Obviously the wet-season peaks must be lowered to prevent flooding and to minimize fill requirements if development is to be economically feasible in many areas. But if gated controls could be installed on canals in areas of low water levels-such as near coastal areas-the wet-season peaks would still be lowered, but the increased water levels during the dry season would increase aquifer storage, thereby providing a larger ground-water supply when demand is greatest. HYDRAULIC PROPERTIES Several determinations of hydraulic properties of the shallow aquifer in the Naples well field area have been made since 1952. In the original well field in the southern part of the city, the average transmissivity was 98,000 gpd (gallons per day) per foot, and the

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22 BUREAU OF GEOLOGY average storage coefficient was 0.0006 (Klein, 1954). In the southern part of the existing well field the transmissivity is 185,000 gpd per foot, and the storage coefficient is 0.0004 (Sherwood, 1961). Both storage coefficients are very low and reflect an artesian rather than a water-table condition: discontinuous overlying beds of low permeability cause the shallow aquifer to react to short-term stresses as an artesian aquifer. The specific capacity of a well is the number of gallons of water produced per foot of drawdown when the well is pumped at a certain rate for a specific time. Using a method developed by Hurr (1966), transmissivities ranging from 500,000 to over 800,000 gallons per day per foot were obtained from specific capacities of test wells along the Alligator Alley and east of Naples. These data indicate that the permeability of the shallow aquifer in this area is several times that in the Naples well-field area. The downstream pick up in flow in the Golden Gate Canal system during two periods in 1969 (see Surface Flow System section) indicated hydraulic connection between the aquifer and the canal. To confirm this connection, five wells (see fig. 9) on the west side of SR 951 (Henderson Creek Road) and about 100 feet from Henderson Creek Canal were pumped November 1, 1970. The specific conductance of the water pumped was determined at the beginning and end of each pumping test. The specific conductance of water from Henderson Creek Canal-sampled opposite the well being pumpedwas determined only at the end of each pumping test. The results of those tests are listed below: CONDUCTANCE (micromhos at 770F) TIME HENDERSON WELL NO. DEPTH DRAWDOWN DISCHARGE BEGIN END CREEK CANAL (feet) (feet) (gpm) C-450 31.7 0.22 250+ 1000 900 785 C-449 31.5 0.49 200 1600 1350 845 C-448 23.5 5.81 200 850 820 815 C-447 22.3 4.57 200 1220 1170 1100 C-446 24.7 3.80 200 790 840 1000 The table indicates hydraulic connection between the aquifer and the Henderson Creek Canal in that where the canal water is fresher than the ground water, the water from the well freshens with pumping; where the canal water is less fresh, the water from the well increases in salinity with pumping.

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REPORT OF INVESTIGATION NO. 63 23 FLORIDAN AQUIFER In recent years waste water has been injected into the lower part of the Floridan aquifer at several locations in southeast Florida. At two locations, treated sewage is being injected and at a third, industrial water. The industrial well and one sewage disposal well are finished in the "boulder zone" of the aquifer, 2,000 to 3,000 feet below msl; the other sewage well is slightly more than 1,000 feet deep. The suggestion has been made that the Floridan aquifer be used also as a storage reservoir for surplus fresh water. During the wet season, fresh water would be pumped into the aquifer though deep wells, and during the dry season the fresh water would be recovered for use. The Floridan aquifer doubtless will become more important when water demands are such that conversion of slightly saline water to fresh water may become feasible. WATER QUALITY Along the coast in western Collier County, the quantity and quality of water are of equal concern because without sufficient quantity to maintain high fresh-water levels near the coast, salty water from the gulf would contaminate ground water of good quality. Eastward expansion of the city of Naples well field is not practical because immediately east of the city mineralized ground water occurs at relatively shallow depth in the shallow aquifer. However, the shallow aquifer 15 miles east of Naples seems to contain large quantities of ground water that is equal in quality to that of the coastal area. The quality of ground water is determined largely by the quality of the rainfall, the materials through which the ground water moves, and the length of time involved in the movement of the ground water through the rocks and soil and down the streams. Domestic and industrial wastes as well as sea water are sources of mineral or biological contamination of streams and ground water. NATURAL CONSTITUENTS SURFACE WATER: Changes in water quality in the surface flow system are greater and more frequent than they are in the aquifer. This is due mainly to the system collecting unfiltered overland flow and lack of filtering in the open channels. When no overland flow

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TABLIE 2,--CHIMICAL ANALYSES OF WATER FROM SELECTED CANALS IN WESTERN COLLIER COUNTY, (results in millligram per liter except where noted) station or fot Phoaphorus Bite number ofl -oB Q t I I I I .4 j §| I N1 Gordon River @ 10-26.70 906 7.4 27 25 10 8.4 0.05 0.02 110 18 1.0 68 2.4 260 56 180 0.2 0.02 0.05 218 City Control 24.71 1,700 7.7 10 20 6 1.4 .02 .01 110 81 1.8 190 8.8 264 87 880 .8 .08 .07 217 Structure 8.80-71 82,900 7.6 21 80 7 2.6 ,18 .04 880 590 -6,500 280.0 204 1,700 12,000 1.0 .48 .46 167 6.22-71 84,000 7.6 27 50 25 5.8 .16 .11 870 790 -6,700 250.0 280 1,700 12,000 .9 .91 1.0 189 Golden Gate Canal 10-26-70 708 7,8 27 50 55 7.8 .40 .02 120 5.0 .50 25 .8 816 62 41 .2 .00 .08 259 @ SR 858 Bridge 2. 4-71 810 7.9 21 60 80 7.2 .04 .01 180 7.4 .66 86 1.2 848 70 64 .8 .02 .24 285 0 8-80-71 850 7.7 22 40 20 8.9 .06 .01 120 9.0 -47 1.4 292 67 94 .2 .02 .05 289 1 6.22-71 790 7.9 27 85 80 9.6 .09 .00 120 11 -60 1.5 808 68 120 .2 .05 .10 258 Gordon River 10-26-70 88,400 7.6 80 85 15 4.6 .16 .02 840 760 4.2 6,600 260 216 2,000 12,000 1.0 .12 .14 177 U.S. 41, Bridge 2471 40,000 7.6 19 20 5 4.2 .11 .04 840 500 10 8,100 810 196 2,100 14,000 1.5 .56 .57 161 0 8-80-71 47,000 7.7 28 20 10 8.0 .15 .08 880 580 -11,000 880 164 2,400 18,000 1.4 .69 .76 185 6-22.71 84,000 7.8 80 80 5 4.5 .09 .02 820 810 -6,700 250 192 2,000 12,000 .9 .54 .60 157 Golden Gate 10-26-70 688 7.5 29 80 55 8.8 .29 .01 120 4.4 .54 20 .8 822 66 28 .8 .01 .01 264 Canal Tributary 24.71 680 7.7 20 70 80 5.8 .12 .01 180 5.2 5.6 10 1.0 848 62 24 .8 .02 .16 285 8-80-71 640 7.6 20 60 40 7.6 6 ..01 110 4.6 -18 .8 812 48 24 .2 .02 .05 256 6-22-71 650 7.7 28 70 40 8.4 .16 .01 110 8.6 -18 .6 800 48 26 .2 .04 .09 246 Cocohatchee River 6-19-70 500 8.0 22 40 25 7.6 --98 2.6 -12 .8 268 26 18 .4 .05 .05 220 Canal nr Naples, Fla. Henderson Creek 5-19-70 1,200 8,2 29 40 15 18 --110 28 -120 4.5 824 84 210 .8 .08 .05 266 Canal nr Naples Fahka Union Canal 2-17-70 780 7.8 28 25 -5.1 --120 5.8 .80 87 7 854 16 68 .2 --290 nr Everglades City

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TABLE 2. (CONTINUED) Hardness Dissolved as OaCOs solids Nitrogen (N) Station or o. o.o1 .o ooo o « Sitenumber P -.' a a Gordon River i 880 120 578 510 0.05 0.04 0.002 0.01 0.000 0.01 0.8 0.2 0.1 0.00 0.00 0.1 0.09 0.70 City Control 400 190 955 940 .07 .08 .010 .01 .000 .01 ---.07 .08 .0 .01 .86 .0 3 Structure 8,800 8,100 -21,500 .11 .07 .004 .05 .000 .02 ---.86 .80 .0 .01 .85 .1 4,200 4,000 -21,900 -.09 .000 .08 .000 .04 ---.26 .89 .1 .08 -5:0 Golden Gate Canal 820 62 478 420 .02 .08 .004 .01 .000 .00 .9 .2 .14 .00 .01 .1 .09 .60 @ SR 858 Bridge 860 71 502 490 .08 .05 .010 .00 .010 .01 ---.04 .08 .0 .02 .81 .0 840 97 568 490 .08 .06 .080 .00 .000 .02 ---.09 10. .0 .01 .55 6.0 840 92 568 840 -.07 .001 .01 .000 .02 ---.04 .08 .4 .08 6.0 Gordon River @ 4,000 8,800 -22,100 .06 .04 .001 .02 .000 .01 40 .2 2.6 .40 .00 .0 .08 .62 U.S. 41 Bridge 2,900 2,800 -25,000 .07 .09 .010 .08 .040 .00 ---. -.40 .49 .1 .04 ..94 .0 8,800 8,200 -82,800 .16 .07 .008 .06 .000 .01 ---.20 1.1 .0 .08 .70 1.0 4,100 4,000 -22,200 -.07 .000 .04 .000 .01 ---.81 .26 .2 .08 -5.0 Golden Gate 820 54 468 410 .08 .04 .002 .00 .000 .01 1.6 .2 .14 .10 .00 .0 .08 .62 .0 Oanal Tributary 850 62 424 420 .08 .08 .010 .00 .050 .01 ---.08 .08 .0 .01 ..87 .0 290 88 486 860 .09 .11 .008 .00 .000 .01 ---.09 9.7 .2 .02 2.7 18.0 290 44 846 860 -.01 .000 .00 .000 .01 --.04 .08 .0 .02 4.0 Cocohatchee River 260 86 888 00 -------.06 .0 .01 .80 Canal nr Naples, Fla. Henderson Creek 880 110 869 780 ------.-.08 .0 .07 .24 Canal nr Naples Fahka Union Canal 880 44 466 480 ----------.0 .01 -nr Everglades City,

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TABLE 8,-CIIEMICAL ANALYSES OF WATER FROM SELECTED WELLS IN WESTERN COLLIER COUNTY, g (resulta in milligrama per liter except where noted) aHardness Dissolved t as 040(X)0 solids Station or DW % s Bite number Colletion , 3 to I t § I a I Naples well field 9.10.70 7,28 82 0,24 74 18 80 0,0 170 26 285 BEOB TH 1 6-28-69 8.00 27 0.10 188 20 120 284 .24 887 117 912 TH 2 6-24-0 7.82 28 0.06 185 29 105 220 .18 842 114 000 TH 8 6-28.60 7.28 27 0.80 119 26 100 156 .8 840 66 756 TH 4 6-25.69 7.18 28 0.25 119 22 50 122 .27 852 86 686 TH 5 6-24-69 7.98 27 0,20 144 18 89 162 .15 848 88 711 TH 6 6.25-69 7.86 25 0.10 160 26 66 274 .1 860 148 980 NA 7 6-18.70 7.85 81 0.04 95 9.5 8 80 .0 276 0 420 NA 8 6-80.70 7.70 16 0.04 82 15 16 86 .0 267 0 450 NA 9 7-14-70 7.75 88 0.04 96 18 10 86 .0 295 0 420 'USGS 7 64-70 480 7.75 12 0.08 69 4.9 266 1 12 .75 218 245 8 277 8 64-70 610 7.85 82 0.16 101 8.6 854 2 21 .95 290 802 18 878 9 68-70 888 8.10 40 0.08 54 1,7 178 2 20 .85 142 189 9 202 10 68-70 8.05 60 0.08 80 1.2 6 11 .15 77 4 187 11 64.70 620 7.55 12 0.12 74 2,4 262 8 25 .96 216 286 14 810 11A 68-70 700 7.75 20 0,04 85 14 842 27 28 1.0 281 298 81 486 0-802 7-24-59 625 7.6 2 25 0.01 72 16 89 4.6 886 11 82 .0 0,6 260 0 870 0-808 7-28.59 911 7.1 15 25 0.10 170 6,8 26 .2 620 4.4 46 .0 .8 450 24 599 0-804 8-10-69 609 8.1 15 10 0.01 70 16 40 4.6 808 14 41 .4 .2 240 0 865 0-805 8-12-59 1,040 7.6 18 0.00 100 17 88 1,9 290 16 180 .2 290 .8 820 87 688 0-450 111-70 840 7.9 80 10 -180 12 42 2.1 864 75 60 .8 299 .0 870 69 517 500 0-448 111.70 770 8.0 0 8.5 -110 9.8 48 1.6 878 6.2 72 .8 810 .0 820 11 449 440 0-446 111.70 650 8.0 0 7.2 -92 9.6 88 1.6 812 28 42 .2 256 .0 270 14 887 870 IBlack, Crow and Eidsness Inc. test holes and analyses. 'Analyses by Black, Crow and Eldsness, Inc.

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REPORT OF INVESTIGATION NO. 63 27 occurs during the dry season, the canal flow is maintained chiefly by inflow from the aquifer. Evapotranspiration of surface water during the dry season causes chemical constituents to concentrate. Results of analyses of water collected from selected sites in canals (fig. 5) in western Collier County are shown in table 2. The chemical quality of the water is generally good except in the tidal reach of the Gordon River. The increase in concentration of certain chemical constitutents upstream from the control in the Gordon River resulted from sea water topping the control during high tides. Surface water is seldom used in south Florida as a source of municipal supply because fresh ground water is usually available in large amounts and does not require expensive treatment that a surface-water supply needs to make it potable. Marco Island obtains water from a rock pit near the intersection of U.S. Highway 41 and State Road 95 because the rock pit is the nearest source of a dependable fresh-water supply. Of the surface-water flow system of western Collier County, only in the Golden Gate and the Fahka Union Canals is the flow large enough to be considered a permanent source of water. However, during the dry season, when water demands are greatest, the minimum flow in Golden Gate Canal may be inadequate to meet future demands. GROUND WATER: Figure 9 shows the location of wells from which water samples were collected for chemical analyses. Table 3 is a compilation of those analyses. Several of the analyses were made by Black, Crow, and Eidsness as part of a cooperative effort with the county and the Geological Survey. Also included in the table is a representative analysis of ground water from the Naples well field. A comparison of the data in tables 2 and 3 reveals that in some areas ground water is superior in quality to canal water. Also, both the coastal and inland ground water is superior in quality to the grohnd water immediately east of Naples. The area east of SR 951 is a potential source of ground water of good quality. CONTAMINANTS Contamination of water in western Collier County can be natural, man-made, or both. Salt-water intrusion into the aquifer and canals is the most common type of natural contamination in coastal regions; introduction of sewage and industrial wastes into canals or the aquifer constitutes man-made contamination. Because of its proximity, the gulf, is an ever-present source of natural contamina-

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28 BUREAU OF GEOLOGY tion; the free interchange of water between the surface flow system and the aquifer increases the threat of man-made contamination. NATURAL: Salt-water intrusion occurs when fresh-water levels in the aquifer are not of sufficient height above msl to prevent the inland movement of the heavier salt water; lowering water levels, either by pumpage or drainage, upsets the natural balance between fresh water and sea water. The capacity of the well field (1971) in Naples is limited by the threat of salt-water intrusion. Consultants for the city have calculated that withdrawals exceeding 20 mgd along the coastal ridge would lower the water level in the aquifer between the well field and the gulf to the point where salt-water intrusion would be immi-nent. The area 15 miles east of Naples, where the aquifer contains water of good quality, would not be threatened by salt-water intrusion because of the distance inland from the gulf. Another source of natural contamination is residual mineralized water in the shallow aquifer immediately east of the Naples well field. During the drought of 1970-71, the quality of water in the Naples well field deteriorated because this mineralized water migrated into the area of influence of the municipal water-supply wells. The area 15 miles inland would probably not be affected by water from this area of inferior water quality, but further exploratory drilling is needed to determine the eastward extent of the area of mineralized water. MAN-MADE: Man-related contaminants that affect water resources have been categorized by the FWQA (1969) into eight general types: sewage and other oxygen-demanding wastes; diseasecausing agents; plant nutrients; synthetic organic chemicals; inorganic chemicals and other mineral substances; sediment; radioactive substances; and heat. Preliminary data collected from a current supplementary U.S. G.S. study in Collier County indicate man-made contaminants in the water resources of western Collier County are well within the safe limits established by federal water regulatory agencies. WATER USE Naples and the unincorporated areas of Golden Gate Estates and Marco Island maintain the only public water supplies in western Coier County. In 1970 the Naples well field pumped, on the aver-

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REPORT OF INVESTIGATION NO. 63 29 age, 4.4 mgd and Marco Island, slightly less than 1 mgd. It is estimated the Golden Gate Estates well field pumped less than 0.5 mgd during 1970. Acreage for agriculture in the investigation area varies yearly but probably averages approximately 5,000 acres. Average irrigation requirements for all crops are 1.5 to 2 feet per acre, or 6.5 to 10 mgd for the 5,000 acres. In western Collier County most of the crops are irrigated with ground water pumped into conveyance canals and ditches. Probably at least half the ground water pumped is consumed. Most industrial water is obtained from municipal wells that tap the shallow aquifer. Also, private domestic supplies and lawn sprinkling systems plus self-supplied industries probably account for at least 1 mgd from the shallow aquifer. The combined demand approximated 15 mgd in 1970. Canal discharge from the surface-flow system in 1970 averaged about 350 mgd. Consulting engineers for the city of Naples forecast that the maximum daily rate of pumpage at the municipal water treatment plant will exceed 20 mg by 1979. The 1970 maximum daily rate was about 8 mg. The 1979 estimate probably exceeds the amount that can safely be withdrawn from the aquifer by present well-field facilities. Therefore, additional supplies from another source will be needed at that time. Analyses of data from both drilling of test wells and sampling of surface water and ground water indicate that ground water in quantities adequate to serve the future needs of western Collier County can be developed from an area centered about 15 miles east of the Naples city limits along Alligator Alley. Future drilling and chemical analyses will delineate the limits of the source more closely, but available data indicate water of good quality is available for development in the aquifer underlying about a 100-square-mile area. SUMMARY AND CONCLUSIONS Western Collier County has large fresh-water-supply potential because of its 54 inches of rainfall annually and its manmade surface flow system, hydraulically connected to a shallow permeable aquifer. However, water problems exist because the rainfall is not evenly distributed throughout the year, causing salt-water intru-

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30 BUREAU OF GEOLOGY sion to threaten the Naples well field during prolonged dry seasons. Contamination of existing and future ground water supplies is possible by man-related activities and urbanization. The controlled surface-water flow system and the distribution of weirs allow for water control without an excessive lowering of ground-water levels. The system also has the potential for recharging the coastal section of the shallow aquifer during the dry seasons. Variable water quality and inadequate flows during the dry season precludes the use of the surface-water flow system as a direct source of municipal water. Water of good quality is contained in the shallow aquifer along the west coast and for about 2 miles inland. The quality then decreases for about 10 miles inland. East of this area of ground water of poor quality, thick sections of permeable limestone extend from near land surface to a depth of almost 100 feet near SR 951 and from land surface to more than 70 feet near Alligator Alley and SR 29. Quality of the ground water in this area is equal or better than that in the coastal area; the quantity is much greater-perhaps several times that of Naples coastal area. More data collected in western Collier County are necessary to more accurately determine the effects of the surface-water flow system on the shallow aquifer in order for water managers to plan for future water-resources development. In addition, a water-quality monitoring network would be necessary to detect water-quality changes in the surface-ground-water flow system as a result of contaminants by man-related activities. WELL LOGS WELL C-130 Depth, feet below Material land surface Sand, quartz, white in upper part, brown-rust in lower part.. 0-21 Marl, sheily, tan-gray, clayey, sandy; few rock fragments... 21-26 Limestone, soft, marly, very shelly ...................... 26-36 Marl, sandy, shely, brown phosphate material ............. 36 -44 Limestone, gray to cream, very shelly, marl............... 44-51 Marl, tan-cream, sandy, shelly.......................... 51-58 Marl, white to light gray, very shelly and sandy, some Hmestone fragments ............................... 58-63 Limestone, white to gray, shelly, cavernous, sandy......... 6371

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REPORT OF INVESTIGATION NO. 63 31 WELL C-174 Depth, feet below Material land surface Sand, quartz, medium, gray............................ 02 Limestone, tan, hard .................................. 210 Limestone, tan, shelly, softer than above................... 1020 Limestone, white .................................... 2025 Limestone, mostly shell, loosely cemented; thin beds of marl.. 2541 Limestone, white to gray, very shelly..................... 4150 Limestone, white to gray, permeable...................... 5078 Limestone, white, sandy ............................... 7888 Sandstone, calcareous, sand increasing at bottom........... 88 -140 WELL C-185 Depth, feet below Material land surface Sand, quartz ........................................ 09 Marl, dark, hard ..................................... 913 Sand, quartz, fine to medium, marly, very shelly........... 1325 Limestone, white to dark gray, shelly, sandy, permeable ..... 2592 Sand, quartz, very fine, gray to tan..................... 92-115 Sand, quartz, very fine to medium, tan to green, phosphatic... 115 -141 WELL 7 Depth, feet below Material land surface Fill and marl ........................................ 05 Limestone, some shell ................................. 5-45 Sand, quartz, clean ................................... 45-50 WELL 8 Depth, feet below Material land surface Fill ............................................... 0 -4 Limestone, dark gray, permeable, shelly .................. 4-85 WELL 9 Depth, feet below Material land surface Limestone, low permeability, very hard .................. 0-17 Limestone, alternating hard, low permeability layers with soft permeable layers, shelly................ 17-60 Sand, brown, "dirty" .................................. 60-75

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32 BUREAU OF GEOLOGY : WELL 10 Depth, feet below Material land surface FiI. brown ......................................... 05 Limestone, large shells, permeable ...................... 5-32 Limestone, tan, very permeable, sulfur odor............... 32 -62 Limestone, shelly .................................... 62-70 Sand .............................................. 70-82 WELL 11 Depth, feet below Material land surface ill ...... ...................................... 05 Limestone, varying hardness, permeable, shelly............ 5 -67 REFERENCES Davis, J. H, 1943, The natural features of southern Florida, especially the vegetation and the Everglades: Fla. Geol. Survey Bull. No. 25. Federal Water Quality Administration, 1969, Summary and status of water qualty standards for interstate waters of Florida. Hem, J. D, 1959, Study and interpretation of the chemical characteristics of nat'ral water: U.S. Geol. Survey Water Supply Paper 1473. Hurr, RT, 1966, A new approach for estimating Transmissibility from specific capacity: Water Resources Research vol. 2, no. 4, p. 657-664. Klein, Howard, 1954, Ground-water resources of the Naples area, Collier County, Florida: Fla. Geol. Survey Rept. of Inv. No. 11. Klein, Howard, and others, 1970, Some hydrologic and biologic aspects of the Big Cypress Swamp drainage area, southern Florida: U.S. Geo. Survey Open-file Report. Little, J. A, Schneider, R. F., and Carroll, B. J., 1970. A synoptic survey of livnological characteristics of the Big Cypress Swamp, Florida: Federal Water Quality Admin. McCoy, H. J, 1962, Ground-water resources of Collier County, Florida: Fla. GeoL Survey Rept. of Inv. No. 31. Sherwood, C. B. and Klein, Howard, 1961, Ground-water resources of northwestern Collier County, Florida: Fla. Geol. Survey Inf. Circ. 29.

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-FLORIDA-GEOLOGICAL-SURVEY COPYRIGHT NOTICE © [year of publication as printed] Florida Geological Survey [source text] The Florida Geological Survey holds all rights to the source text of this electronic resource on behalf of the State of Florida. The Florida Geological Survey shall be considered the copyright holder for the text of this publication. Under the Statutes of the State of Florida (FS 257.05; 257.105, and 377.075), the Florida Geologic Survey (Tallahassee, FL), publisher of the Florida Geologic Survey, as a division of state government, makes its documents public (i.e., published) and extends to the state's official agencies and libraries, including the University of Florida's Smathers Libraries, rights of reproduction. The Florida Geological Survey has made its publications available to the University of Florida, on behalf of the State University System of Florida, for the purpose of digitization and Internet distribution. The Florida Geological Survey reserves all rights to its publications. All uses, excluding those made under "fair use" provisions of U.S. copyright legislation (U.S. Code, Title 17, Section 107), are restricted. Contact the Florida Geological Survey for additional information and permissions.