Ground water in the Immokalee area, Collier County, Florida ( FGS: Information circular 51 )

STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY

FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director

INFORMATION CIRCULAR NO. 51

GROUND WATER IN THE IMMOKALEE AREA,

COLLIER COUNTY, FLORIDA

By
Henry J. McCoy
U. S. Geological Survey

Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
COLLIER COUNTY COMMISSION
and the
FLORIDA GEOLOGICAL SURVEY

TALLAHASSEE
1967

Completed manuscript received
December 1, 1966
Printed by the Florida Geological Survey (job no. 208)
Tallahassee

ii

TABLE OF CONTENTS

Page

Abstract................................................. 1
Introduction ............................................ 1
Purpose and soope .................................. 1
Geography ............................................. 3
Location and general features ........................ 3
C limate ........................................... 4
Topography and.drainage .............. .......... ..... 5
Water use ............................................. 6
Test-well drilling ...................................... 7
Geology ................................................ 7
Ground water ........................................... 10
Hydrology ....... ..... ..... ... ..................... 12
Quantitative studies ................................ 13
Quality of water .................................... 16
Summary ................................................ 22
References ............................................ 25
Well logs .............................................. 27

ILLUSTRATIONS

Figure
1 Map of Florida peninsula showing location of Collier
County and Immokalee area ...................... 2
2 Map and diagrams explaining well-numbering system 4
3 Graph showing average monthly rainfall at Lake
Trafford, for the period 1951-63, and monthly rain-
fall for 1963 .................................... 5
4 Map showing physiographic areas of Collier County.. 6
5 Map showing location of inventoried wells, test holes,
lines of lithologic logs, and wells sampled for chem-
ical analyses .................... .............. 8
6 Lithologio logs along line A-A' ................... 9
7 Lithologic logs along line B-B' ................... 10
8 Fence diagram showing lithology of subsurface mat-
erials .......................................... 11
9 Graphs showing rainfall and stage at Lake Trafford
and water levels in well 2521-1619 ................ 14
10 Bar graph showing concentrations of chemical con-
stituents in ground water from selected wells in
northwestern Collier County ...................... 18
11 Stiff diagrams showing relative concentrations of
chemical constituents in ground water from wells .... 21

TABLES

Table
1 Chemical analyses of water from wells in the Immo-
kalee area ..................................... 19

GROUND WATER IN THE IMMOKALEE AREA,
COLLIER COUNTY, FLORIDA

By
Henry J. McCoy

ABSTRACT

Potable ground water in the Immokalee area is available at
depths ranging from about 20 to 300 feet below the land surface.
The materials comprising this subsurface section are primarily
quartz sand, marl, shells, and consolidated to semiconsolidated
limestone. Although vertical and horizontal ground-water move-
ment is retarded by marl layers, the section is essentially a single
unconfined aquifer.

The principal chemical constituents of the ground water
are calcium and bicarbonate. The most objectionable constituents
are iron and hydrogen sulfide which occur in small amounts and
both of which can be removed easily and inexpensively.

The shallow coarse sand and gravel beds west and northwest
of Immokalee contain the best quality of ground water in the area
and appear to be the most feasible source for municipal supplies.
A deep limestone section in Immokalee and a shallow limestone
section to the east could be developed for increased future de-
mands. However, detailed studies regarding size, shape, and
hydraulic characteristics of the major producing zones are needed
to determine the overall ground-water potential of the system.

INTRODUCTION

PURPOSE AND SCOPE

Acceleration and expansion of farming in the Immokalee area,
figure 1, during the past 10 years have caused rapid increases in
both permanent and migrant labor populations. The accompanying
demands for increased ground-water supplies and sewage disposal
have been met by individual domestic wells and septic tanks.
However, the concentration of population in the town of Immokalee
and the increasing need for larger water supplies in the near
future have made the need for a central water-supply system

FLORIDA GEOLOGICAL SURVEY

- I cl

i Miles

0 10 miles

Figure 1. Location of Collier County and the Immokalee area.

apparent. Recognizing this, the Board of Commissioners of Collier
County requested the U.S. Geological Survey to investigate the
ground-water resources of the Immokalee area as a part of the
continuing cooperative program started in 1958 between the County
and the Survey.

INFORMATION CIRCULAR NO. 51

The scope of the investigation involved the drilling of test
holes and the detailed inventorying of existing wells in order to
define the location, depth, potential yield, and chemical quality
of the water contained in the shallow aquifer that might be used
for the development of a central water-supply system.

The field work and collection of data for the investigation
covered the period 1961 through 1963. Much of the data collected
for the report on the ground-water resources of Collier County
(McCoy, 1962) is incorporated into this report.

The well-numbering.system used in this report conforms with
the well-numbering system of the Water Resources Division of the
U.S. Geological Survey and is based on a one-second grid of
parallels of latitude and meridians of longitude, figure 2.

The well number is a composite of two numbers separated
by the letter N. The two numbers consist of the digits of the
'degrees, the two digits of the minutes, and the two digits of the
seconds of latitude and longitude. The N indicates "North" la-
titude. If more than one well lies within a one-second grid, the
wells are numbered consecutively and this number is placed at
the end of the well number following the decimal. Hence, the
well number defines the latitude and the longitude on the south
and east sides of a one-second quadrangle in which the well is
located.

Because the Immokalee area lies within the quadrangle formed
by the 260 north latitude parallel and the 810 west meridian of
longitude and each one-second quadrangle does not have more than
one well, these digits, plus the letter N, are deleted from the well
numbers used in this report.

Therefore, well 262627N0812601.1 is referred to in the text
as well 2627-2601.

GEOGRAPHY

LOCATION AND GENERAL FEATURES

Immokalee is an unincorporated community in the northern
part of Collier County, Florida. (see fig. 1). Its principal occu-
pations are truck farming and cattle raising. A large part of its

FLORIDA GEOLOGICAL SURVEY

Figure 2. Well-numbering system.

1960 population of 4,800 was migrant farm laborers. Two main
highways, State 846 and State 29, connect the town with sur-
rounding communities. The town is serviced by bus and railway,
and a small commercial plane airfield.

CLIMATE

The climate of Immokalee is subtropical with an average
annual temperature of 76OF. The warmest months are generally

INFORMATION CIRCULAR NO. 51

The scope of the investigation involved the drilling of test
holes and the detailed inventorying of existing wells in order to
define the location, depth, potential yield, and chemical quality
of the water contained in the shallow aquifer that might be used
for the development of a central water-supply system.

The field work and collection of data for the investigation
covered the period 1961 through 1963. Much of the data collected
for the report on the ground-water resources of Collier County
(McCoy, 1962) is incorporated into this report.

The well-numbering.system used in this report conforms with
the well-numbering system of the Water Resources Division of the
U.S. Geological Survey and is based on a one-second grid of
parallels of latitude and meridians of longitude, figure 2.

The well number is a composite of two numbers separated
by the letter N. The two numbers consist of the digits of the
'degrees, the two digits of the minutes, and the two digits of the
seconds of latitude and longitude. The N indicates "North" la-
titude. If more than one well lies within a one-second grid, the
wells are numbered consecutively and this number is placed at
the end of the well number following the decimal. Hence, the
well number defines the latitude and the longitude on the south
and east sides of a one-second quadrangle in which the well is
located.

Because the Immokalee area lies within the quadrangle formed
by the 260 north latitude parallel and the 810 west meridian of
longitude and each one-second quadrangle does not have more than
one well, these digits, plus the letter N, are deleted from the well
numbers used in this report.

Therefore, well 262627N0812601.1 is referred to in the text
as well 2627-2601.

GEOGRAPHY

LOCATION AND GENERAL FEATURES

Immokalee is an unincorporated community in the northern
part of Collier County, Florida. (see fig. 1). Its principal occu-
pations are truck farming and cattle raising. A large part of its

INFORMATION CIRCULAR NO. 51

July and August. The average annual rainfall is 52 inches. More
than half the yearly rainfall occurs during June through September.
Figure 3 shows the average monthly rainfall at Lake Trafford,
near Immokalee, for the period 1951-63 and monthly rainfall for
1963.

EXPLANATION

9 1951- --1963
1963

07-
z 6

4

JAN. FEB. MAR APR. MAY. JUN. JUL. AUG. SEPT. OCT. NOV. DEC.

Figure 3. Average monthly rainfall at Lake Trafford,- for the period
1951-63 and monthly rainfall for 1963.

TOPOGRAPHY AND DRAINAGE

Immokalee is in the Flatlands physiographic area of Collier
County as shown in figure 4 (Davis, 1943). The Flatlands is cha-
racterized by flat sandy areas, marshes, cypress stands, and open-
water depressions. The elevation of the land surface is about
35 feet above msl (mean sea level). Except for high dunes on
Marco Island (fig. 4), the highest elevations in the county, 42
feet, occur immediately north of Immokalee.

Drainage of the Immokalee area is generally westward toward
Lake Trafford by way of sloughs and marshes, and southward
through ditches and canals. Ditches and canals have improved
the otherwise sluggish natural drainage.

FLORIDA GEOLOGICAL SURVEY

Figure 4. Physiographic areas of Collier County.

WATER USE

Ground water is the source of all irrigation and domestic
supplies in the Immokalee area. Because the community does not
have a central water-supply system and has little industry other
than agriculture, the per capital use of water in the Immokalee
area is probably about 50 to 75 percent of the national average
of 150 gallons per day (Leopold and Langbein, 1960). Therefore,
using 4,500 as the population for the period of investigation, an
estimate of daily water use for the Immokalee area would be in
the range of 0.3 to 0.5 mgd (million gallons per day).

The principal crops grown in the Immokalee area are tomatoes,
peppers, cucumbers, and watermelons and are irrigated by pumping

INFORMATION CIRCULAR NO. 51

ground water into ditches that dissect the fields. Estimates of
water requirements for these crops are about .01 acre-foot (3,250
gallons per acre) per day (County Agent, personal communica-
tion). Assuming that an average of 5,000 acres were irrigated
daily for the period of record, an estimate of daily water use for
irrigation in the Immokalee area would be about 16 mgd.

TEST-WELL DRILLING

Three test holes were drilled in the Immokalee area during
the countywide study but the location and extent of the major
water-bearing formations in the Immokalee area could not be de-
termined from this number of test holes. As a part of the present
study, five additional test wells were drilled to depths of about
120 feet during the summer of 1961, as shown in figure 5. Rock
cuttings and water samples were taken systematicallyiduring the
drilling of each hole. Logs of the eight exploratory holes are
given at the end of this report.

GEOLOGY

In the Immokalee area, the primary source of ground water is
the permeable sediments in the uppermost 200 feet of the subsur-
face. This 200-foot section comprises mostly quartz sand, marl,
shell beds, and consolidated and semiconsolidated limestone.
The well logs in figures 6 and 7 and the lithologic fence diagram
of figure 8 indicate that the materials change markedly with depth
and location. Correlation between wells is extremely difficult
because of the nonuniformity of sediments.

The materials in the lower 100 feet of the 200-foot section
are probably of late Miocene age and are similar to the Tamiami
Formation throughout most of Collier County, except for the ab-
sence of consolidated limestone. The gravel and coarse sand
beds of the upper 100 feet of the 200-foot section of permeable
sediments are somewhat unique to the Immokalee area and may
have been deposited by large late Miocene and pre-Pleistocene
deltaic streams that extended southward from the Highlands Ridge
(Bishop, 1956, p. 26). The shape, size, and texture of the mater-
ials composing the gravel beds, plus the presence of fresh-water
shells and marls suggest that they were deposited in a lagoon or
delta. The rapid vertical and horizontal changes in *occurrence
of the gravel beds could be attributed to streams changing fre-

8 FLORIDA GEOLOGICAL SURVEY

ItSE 28 Eh 2E 26~30
..-.. --1291-2

r^ EXPLANXrG H i 1 I

Inte
S ft 1 and untr hi g1
"1-hu0 coapae whmcal

"est hol Oand nb W
Ulft a W*of I" 2744-26M2
Lt- ci b.. I % -
(2 an flog

SE ---261 6-2327

logs, and wells sampled for cemia2616327 aBalyses
------ 2530-2611 25 -0
S 2502-2418e
^ ^^ V A ~ _,~- -*- \" '-P 9 --- ,r 4^ ^- --l

S- --- --- 245 25541 2506-24 2507-2357

2 L21.- -L-. 1 r

A AJ

Figure 5. Location of inventoried wells, test holes, lines of lithologic
logs, and wells sampled for chemical analyses.

INFORMATION CIRCULAR NO. 51

OJ
C?
(D
N

Figure 6. Lithologic logs along line A-A*.

quently on an ancient delta and to subsequent reworking of the
deposits by wave action.

The surficial sands in the Immokalee area were deposited on
the ocean floor during the Pleistocene Epoch when sea level was
about 42 feet higher than at present. During a particular stand of
the sea, the sands from rivers and streams settled in the shallow
water near shore. These ancient sea floors are known as terraces
and are recognizable throughout the Atlantic Coastal Plain. Al-
though similar in composition to the surface sands in the Immo-

FLORIDA GEOLOGICAL SURVEY

Figure 7. Lithologic logs along line B-B'.

kalee area, the surface sands throughout the rest of Collier County
were deposited when sea level was only about 25 feet higher than
at present.

Information from test drilling indicates that the limestone
that occurs at shallow depths throughout the rest of the county
pinches out as it approaches the Immokalee area from the south-
west, south, and east.

GROUND WATER

Ground water occurs in permeable subsurface formations
called aquifers. If the ground water is unconfined and under atmos-
pheric pressure, its upper surface is called the water table. The
slope of the water table indicates the direction of movement of
unconfined ground water. Unconfined, or nonartesian aquifers
are replenished by the downward infiltration of rainfall, or by

INFORMATION CIRCULAR NO. 51 11

2627-2701

C-- mile

2C -

30

2627-260

/ miles
2542-2506
S256-2426
2504-
8 16-2327
5052558

2442- -- 418,
2517 2507-2357

Index mop showing location of wells
used in fence diagram.

Figure 8. Lithology of subsurface materials.

FLORIDA GEOLOGICAL SURVEY

downward seepage from lakes and rivers. This replenishment, or
recharge, generally occurs in varying degree throughout the extent
of the aquifer.

Data from test holes in the Immokalee area indicate the ground
water to a depth of nearly 300 feet is unconfined or partly con-
fined. The presence of marl beds throughout the section suggests
that partly confined conditions may exist in areas where the marl
beds of low permeability separate the water-bearing zones on the
top and bottom. However, the partly confined zones appear to be
of limited areal extent and therefore have little significance as
large water-bearing reservoirs.

Domestic and industrial wells in the Immokalee area range
in depth-from 22 to 292 feet below the land surface. Large esta-
blishments such as the packing houses usually obtain ground-
water supplies from consolidated materials at depths greater than
150 feet.

Fifteen or more years ago, large quantities of ground water
for irrigation were derived from the artesian Floridan aquifer which
underlies the Immokalee area at a depth of about 400 feet (McCoy,
1962, p. 18). However, because the artesian water is highly miner-
alized, smaller wells developed in the shallow aquifer have re-
placed nearly all of the deep artesian wells. Many of the remaining
artesian wells are still serviceable and could be used as a supple-
mental source to mix with the shallow ground-water supplies during
droughts.

Because the Floridan aquifer contains tremendous quantities
of water, it should not be ignored because of its mineralization. As
domestic and agricultural demands for ground water increase in
the future, the importance of the artesian aquifer as a potential
source of ground water will also increase.

HYDROLOGY

In the Immokalee area, surface-water bodies are directly con-
nected to the shallow aquifers. Levels of lakes and canals reflect
essentially the elevation of the water table.

The shallow aquifer in the Immokalee area is recharged prin-
cipally by local rainfall. During the rainy season some of the

FLORIDA GEOLOGICAL SURVEY

Figure 7. Lithologic logs along line B-B'.

kalee area, the surface sands throughout the rest of Collier County
were deposited when sea level was only about 25 feet higher than
at present.

Information from test drilling indicates that the limestone
that occurs at shallow depths throughout the rest of the county
pinches out as it approaches the Immokalee area from the south-
west, south, and east.

GROUND WATER

Ground water occurs in permeable subsurface formations
called aquifers. If the ground water is unconfined and under atmos-
pheric pressure, its upper surface is called the water table. The
slope of the water table indicates the direction of movement of
unconfined ground water. Unconfined, or nonartesian aquifers
are replenished by the downward infiltration of rainfall, or by

INFORMATION CIRCULAR NO. 51

higher parts of the county north of Immokalee are inundated and
overland and groundwater flow enter the area to recharge the aqui-
Fer.

Canal flow and evaporation from open bodies of water are the
principal means of surface-water discharge in the Immokalee area
and are greatest during the rainy season.

Irrigation, evapotranspiration, and domestic use are the prin-
cipal means of ground-water discharge. The significance of irri-
gation discharge is more pronounced during the dry winter months
when farming is at a maximum.

In the Immokalee area the water level fluctuates in response
to rainfall, evapotranspiration, and pumping. Figure 9 shows hydro-
graphs of daily rainfall and stage at Lake Trafford and a well
54 feet deep, 8 miles east of Immokalee. The fluctuations of the
lake stage and the water level in the well are similar. Both levels
rise in response to increased rainfall and fall during decreased
rainfall. The "saw-tooth" pattern of fluctuations of water levels
in the well is due primarily to nearby irrigation wells being pumped
periodically. The hydrographs show that the range of fluctuation
of the water levels in 1963 was about 4 to 5 feet and probably
reflect the range of the water-table fluctuation throughout most
of the area. Some outlying areas around Immokalee are drainedby
canals to reduce flooding thereby preventing large fluctuations of
the water table.

The subsurface material changes markedly in short distances
and with depth; these differences result in changes in both hori-
zontal and vertical permeability. In the area northwest of Immo-
kalee, shallow (50-foot) irrigation wells pumping at 150 gpm
(gallons per minute) produce drawdowns of about 5 feet or more,
while in the area east of Immokalee, wells of similar depths (51
and 54 feet) discharging 1,000 gpm produce equal or less draw-
down. This is due chiefly to the differences in aquifer permeabi-
lity. Wells in the eastern area penetrate a limestone of very high
permeability, while those in the northwestern area tap sandy mater-
ials of much lower permeability.

QUANTITATIVE STUDIES

To determine the ground-water potential of an area, the hy-
draulic properties of the aquifers must be known. The principal

FLORIDA GEOLOGICAL SURVEY

C

4.6 for month

J F M A M J "J A S 0 N D
1963

Figure 9. Rainfall and stage at Lake Trafford and water levels in well
2521-1619.

hydraulic properties of an aquifer are its capacities to transmit
and store water. If less permeable beds are present above or below
the aquifer, leakage through those beds is also important to the
overall potential of the hydraulic system. The aquifer properties
are generally expressed as coefficients of transmissibility, sto-
rage, and leakance. The most commonly used method for deter-
mining these properties is by an aquifer test wherein a well pene-
trating the aquifer is pumped and its effect on the water table is
observed in other wells in the vicinity of the pumped well.

14

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Ut
ri

Lu

m,

UtJ
LL
z

!-

_cn
JLtl

Lrz
Cr z

If-

INFORMATION CIRCULAR NO. 51

The coefficient of transmissibility (T) is a measure of the
capacity of an aquifer to transmit water. In customary units it is
the quantity of water that will flow through a vertical section of
the aquifer 1-foot wide and extending the full saturated height,
under a unit hydraulic gradient, at the prevailing temperature of
the water (Theis, 1938, p. 892). The coefficient of storage (S) is
a measure of the capacity of an aquifer to store water and is
defined as the volume of water released from or taken into sto-
rage per unit surface area of the aquifer per unit change in the
component of head normal to that surface. The coefficient of
leakance characterizes the ability of semiconfining beds above or
below an aquifer to transmit water to the aquifer (Hantush, 1956,
p. 702). It is defined as the quantity of water that crosses a unit
area at the interface between the main aquifer and its confining
bed, if the difference between the head in the main aquifer and
in the beds supplying the leakage is unity.

Two tests were made in the Immokalee area. The locations
of the tests were determined by the availability of wells pene-
trating the aquifer that could be used for pumping and for observ-
ing fluctuations of the water table. The site of the first test was
about 8 miles east of Immokalee at the Collier County line (Klein
and others, 1962). A large diameter irrigation well was pumped
at a rate of 1,300 gpm for 25 hours. Analyses of the data from the
observation wells indicated that T was 960,000 gpd/ft (gallons
per day per foot), S was 0.00031, and the coefficient of leakance
was 0.0000011 gpd/sq ft/ft (gallons per day per square foot per
foot of vertical head) of vertical head.

The second test was made at an abandoned farm about 5
miles northwest of Immokalee. A 6-inch well was pumped at a
rate of 152 gpm for 44 hours. Values for T, S, and leakance were:
60,000 gpd/ft, 0.00025, and 0.00086 gpd/sq ft/ft of vertical head,
respectively.

The differences in values of the coefficients for the two sites
are due to differences in lithology in the two areas. The principal
aquifer in the area east of Immokalee is composed of highly per-
meable solution-riddled limestone which exceeds 35 feet in thick-
ness. This accounts for the large value of T. The lime-
stone section is overlain by 5 feet of surficial, medium-
grained sand and 17 feet of sandy clay which retards downward
leakage. On the other hand, the aquifer northwest of Immokalee

FLORIDA GEOLOGICAL SURVEY

which is composed chiefly of sand, is considerably less permeable
than the limestone aquifer, but it receives a larger amount of
recharge by vertical leakage. This is probably because the over-
lying sands in the northwestern area contain less marl and there-
fore are more permeable than the overlying materials in the eastern
area.

Of the five wells inventoried that are reported to be finished
in the gravel and coarse sand beds, three are used for farm irri-
gation. No detailed pumping data are available for the three wells
but personal communications with the farmers indicated that the
wells are pumped between 750 and 1,000 gpm for varying periods
each day with 10 feet or less drawdown of the water table near
the pumped well. If additional test drilling indicates the gravel
and coarse sand beds to be thick and continuous over a wide-
spread area it appears these beds would be adequate to furnish
ground-water supplies to a municipal system for present water
requirements. However, aquifer tests would be required to deter-
mine optimum spacing and discharge of wells to meet present and
near future demands.

QUALITY OF WATER

The chemical composition of ground water in an area is deter-
mined principally by the type of water which recharges the aquifer,
the character of the geologic materials through which the water
passes, the duration of contact and chemical reaction between the
water and rock, and the effects of human activity. Most public
drinking-water supplies in the United States strive to conform to
standards established by the U.S. Public Health Service for water
used on interstate carriers. Below are some of the more common
chemical constituents and properties and the maximum amounts
recommended by the U.S. Public Health Service (1961) in parts
per million:
Alkyl benzene sulfonate (detergents) ................. 0.5
Arsenic........................................... 0.01
Chloride .......................................... 250.0
Fluoride .......................................... 1.0
Iron ............................................. .0.3
Manganese ........................................ 0.05
Nitrate ........................................... 45.0
Sulfate (S04) .......................................... 250.0
Total dissolved solids ............................. 500.0

INFORMATION CIRCULAR NO. 51

Iron in concentrations greater than that listed above is object-
ionable because it imparts a disagreeable taste and it quickly
discolors objects with which it comes into contact. Its presence
in ground water in the Immokalee area is unpredictable as to
depth and location. Fortunately, iron can be removed easily by
aeration and filtration.

Hardness is a measure of the calcium and magnesium content
of ground water and is customarily expressed as the equivalent of
calcium carbonate. Water having a hardness less than 60 ppm
(parts per million) is rated as soft; 60 to 120 ppm, as moderately
hard; and more than 120 ppm, as hard. Water having a hardness of
more than 200 ppm ordinarily requires softening for most uses.

The pH indicates the acidity or alkalinity of water. The pH
scale ranges from 0 to 14. A pH value of 7 indicates neutral water;
values less than 7 denote increasing acidity, and those greater
than 7 denote increasing alkalinity.

Water samples from 16 wells were analyzed to determine the
quality of water in the Immokalee area, as shown in figure 10.
Complete chemical analyses were made on 10 of the samples and
determinations of selected constituents were made on the remaining
6 samples. The results of the analyses are given in Table 1.
The depths of the 16 wells range from 22 to 292 feet below the
land surface. The wells are used for domestic, industrial or public
supplies, and for irrigation.

The bar graph in figure 10 shows the concentration of six
important chemical constituents in the ground water from 10 loca-
tions in the Immokalee area. Analyses of water from four other
locations in Collier County are included for comparison.

The constituents in Table 1 are expressed in parts per million.
This compares the concentrations of constituents in solution by
weight. Equivalents per million is used in figure 10 and takes
into account not only weight concentrations but also the concept
of chemical equivalence. Expressing concentrations in equiva-
lents per million means the constituents are also chemically
equivalent. When all constituents have been determined, the total
equivalents on one side of the bar in the-ar-graph should very
nearly equal the equivalents on the other side of the bar (Hem,
1959).

CALCIUuM(Cl BICAMIONIATE (COl,
MAONEflUM IMI 1 U SLFAT 10s) _____
SODIUkM Ia CLO1f0 CI aI

* WEST AND NORTHWEST IMMOKALEE
EAST IMMOKALEE
I -

Figure 10. Bar graph showing concentrations of chemical constituents in ground water from selected wells in
northwestern Collier County.

1__1~

Table 1.--Chemical analyses of water from wells in the ILmokalee area.

per million except those for color, pH, and specific conductance)
(Analyses by U. S. Geological Survey)

Sa ,,Hardness

I4 as CaCO3 i

242 a 1 | I |
_U _. r 1 d p' 1
f I 1_ I I a -

2441-2517

2459-2554

2506-2437

2507-2418

2521-1619

2521-2631

2527-2442

2530-2611

2555-2628

2556-2603

2542-2506

2542-2506

2617-2601

2707-2605
2744-2632
2911-2701

22.5

5.5

5.5

7.5

22.0

69.0

5.5

38.0

6.0

12.0

11.0

15.0

10.0

17.0

6.0
11.0

10-09-61

10-09-61

06-09-61

06-21-61

03-10-55

10-09-61

05-16-58

10-09-61

10-09-61

10-22-63

06-22-61

06-22-61

10-22-63

10-22-63

10-22-63
10-22-63

0.2

0.2

0.3

0.2

0.0

0.2

0.5

0.1

0.2
1.3

0.3

School

Domestic

do

Public

Test

Observation

Domestic

Industrial

Domestic

do

do

Test

do

Sprinkler

Irrigation
do
do

353 583 -- 10

83 -- 99 -- 5

31 -- -- 53 -- 5

244 162 0 346 8.5 7

312 208 0 472 8.5 8

534 353 -- 876 7.3 75,

15 -- 34 -- --

407 338 9 702 7.7 25

235 -- -- 372 -- 5

43 -- 71 -- --

78 21 18 97 5.3 5

232 198 18 396 8.2 7

218 132 0 312 8.2 12

74 13 8 84 5.5 10

68 40 4 100 6.7 5
86 30 6 99 6.5 5

422 272 0 659 7.9 30

(Results in parts

1/ In solution at time of analysis

4

4

1

3

1!

4

1
24

0.11

.98

2.3

6.0 .01

6.0 0.0

7.0 .36

.98

0.0 .02

.35

4,10

8.9 .11

9.0 0.01

0.0 0.10

9.1 0.40

9.9 0.02
'.0 0.03

-- .

58.0

70.0

114.0

98.0

5.2

77.0

45.0

3.2

16.0
10.0
79.0

4.3

8.1

16.0

22.0

1.9

1.5

4.7

1.2

0.0
1.2
18.0

13.0

23.0

50.0

18.0

5.5

5.3

17.0

9.0

3.1
5.0
40.0

192

242

451

402

3

220

178

6

44
29

336

0.2

0.1

2.0

0.1

0.0

0.2

0.2

0.0

0.2
0.0

0.0

54.0

0.10

19.0

3.6

3.6

4.8

1.2
0.4

1.6

1.5
0.9

.o0

[

FLORIDA GEOLOGICAL SURVEY

The five wells in the western and northwestern parts of the
Immokalee area (2911-2701, 2707-2605, 2617-2601, 2744-2632, and
2556-2603) are reported to be finished in gravel beds ranging in
depth from 22 feet to 89 feet. However, the chemical content of
the water from well 2911-2701 (4% miles northwest of Immokalee)
(fig. 10) appears to be similar to that of well 2527-2442 ( mile
southwest of airfield) which is finished in limestone. Well 2521-
1619, 54-feet deep, located about 8 miles east-of :Immokalee (see
fig. 10), draws water from the highly permeable shallow limestone.
This probably accounts for the large amount of dissolved solids,
chiefly calcium bicarbonate, in the water sample. Well 2527-2442
furnishes industrial water supplies for a large packing house in
Immokalee. The well is finished in a sandy, poorly-consolidated
limestone at a depth of 292 feet.

Figure 11 illustrates with more clarity any differences in
water quality between wells of various depths in the Immokalee
area. Each diagram was constructed by determining the percentage
of a constituent to the total concentration of each group of con-
stituents; for example, the value for calcium was determined by
dividing its concentration by the total concentration of calcium
magnesium, and sodium-potassium. The same procedure was used
for the right side of each diagram.

Water of good quality is represented in figure 11 by a diagram
which has a broad top and a narrow base. Wells 2542-2506, 2707-
2605, and 2506-2437 are examples of this characteristic. The
diagrams make it obvious that the primary constituents in the
water from all but two of the wells are calcium and bicarbonate.
The diagrams do not account for differences in total dissolved
solids between water samples. For example, water from wells
2556-2603 and 2617-2601 contain primarily sodium-potassium and
chloride and appear to have considerably larger amounts of these
constituents than do the other waters. However, the chloride
content of well 2556-2603 is 11 ppm and that of well 2542-2506 is
15 ppm. This is because well 2542-2506 has about 3 times as
much total dissolved solids as does well 2556-2603.

The abnormal diagrams for wells 2556-2603 and 2617-2601
must be attributable to some factor other than shallow depth. Well
2542-2506 is similar in depth to wells 2556-2603 and 2617-2601
yet its diagram is comparable to the majority of the other wells.
Well 2542-2506 is finished in a sandy limestone overlain by essen-

WELL 2556 -2603
IT

DISSOLVED SOLIDS'78
tOTAL DEPTH = 37'

WELL 2542-2506

DISSOLVED SOLIDS 232
TOTAL DEPTH= 23'

WELL 2707-2605

DISSOLVED SOLIDS 40
TOTAL DEPTH 64'

WELL 2521-1619
I _I

DISSOLVED SOLIDS'534
TOTAL DEPTH = 54'

WELL 2617-2601

DISSOLVED SOLIDS= 74
TOTAL DEPTH = 22'

WELL 2506-2437

DISSOLVED SOLIDS 244
TOTAL DEPTH= 126'

WELL 2507-2418

DISSOLVED SOLIDS= 312
TOTAL DEPTH= 105'

EXPLANATION
PER CENT
100. 50 0 50 100
C I ----HCO

No+K-- 4- _-C,

Figure 11. Stiff diagrams showing relative concentrations of chemical constituents in ground water from wells.

WELL 2744-2632

DISSOLVED SOLIDS" 86
TOTAL DEPTH 80'

WELL 2542-2506

DISSOLVED SOLIDS= 218
TOTAL DEPTH 118'

WELL 2911-2701

DISSOLVED SOLIDS=422
TOTAL DEPTH = 89'

FLORIDA GEOLOGICAL SURVEY

which is composed chiefly of sand, is considerably less permeable
than the limestone aquifer, but it receives a larger amount of
recharge by vertical leakage. This is probably because the over-
lying sands in the northwestern area contain less marl and there-
fore are more permeable than the overlying materials in the eastern
area.

Of the five wells inventoried that are reported to be finished
in the gravel and coarse sand beds, three are used for farm irri-
gation. No detailed pumping data are available for the three wells
but personal communications with the farmers indicated that the
wells are pumped between 750 and 1,000 gpm for varying periods
each day with 10 feet or less drawdown of the water table near
the pumped well. If additional test drilling indicates the gravel
and coarse sand beds to be thick and continuous over a wide-
spread area it appears these beds would be adequate to furnish
ground-water supplies to a municipal system for present water
requirements. However, aquifer tests would be required to deter-
mine optimum spacing and discharge of wells to meet present and
near future demands.

QUALITY OF WATER

The chemical composition of ground water in an area is deter-
mined principally by the type of water which recharges the aquifer,
the character of the geologic materials through which the water
passes, the duration of contact and chemical reaction between the
water and rock, and the effects of human activity. Most public
drinking-water supplies in the United States strive to conform to
standards established by the U.S. Public Health Service for water
used on interstate carriers. Below are some of the more common
chemical constituents and properties and the maximum amounts
recommended by the U.S. Public Health Service (1961) in parts
per million:
Alkyl benzene sulfonate (detergents) ................. 0.5
Arsenic........................................... 0.01
Chloride .......................................... 250.0
Fluoride .......................................... 1.0
Iron ............................................. .0.3
Manganese ........................................ 0.05
Nitrate ........................................... 45.0
Sulfate (S04) .......................................... 250.0
Total dissolved solids ............................. 500.0

FLORIDA GEOLOGICAL SURVEY

tially clear sand. Wells 2556-2603 and 2617-2601 are reported to
be finished in the gravel and coarse sand beds overlain by highly
organic sands and marls. Leaching of these organic zones by
downward filtering rainwater may be the cause of higher concen-
trations of sodium, potassium, and chloride in the two wells.

Table 1 and figure 10 indicate that water from all wells sam-
pled is chemically suited for domestic use, but the water in the
gravel and coarse sand beds in the western and northwestern part
of the area would require the least treatment for use as a muni-
cipal supply. However, available data are insufficient to determine
accurately the areal extent, thickness, and water-bearing charac-
teristics of these beds. If a municipal supply is to be established
in Immokalee, more detailed test drilling and aquifer tests are
needed there to determine the hydraulic characteristics of the
individual lithologic types. Because of the satisfactory quality
of the water, the shallow depth, and close proximity to the town,
the gravel and coarse sand beds appear to be the most feasible
aquifer to develop. If testing proves the beds to be too localized
and the needed quantity of water cannot be obtained, the gravel
and sand beds and the deep limestone aquifer may be utilized
as a dual source. The permeable shallow limestone to the east
can be utilized to meet future demands.

SUMMARY

Potable ground water is available throughout the Immokalee
area to a depth of about 300 feet. The subsurface materials are
primarily quartz sand, consolidated and semiconsolidated lime-
stones, marl, and shell beds, and can be considered as a single
unconfined aquifer. However, because individual layers are, for
the most part, discontinuous both vertically and horizontally,
there may be areas where the aquifer is confined and where yields
may be low.

The principal chemical constituents in the ground water are
calcium and bicarbonate. The difference in mineral composition
within the aquifer seems to be the chief reason for the difference
in quality of the water between locations. The ground water of the
sand and gravel sections in the western and northwestern part of
the Immokalee area contains from 40 to 232 ppm of dissolved
solids, as compared to 534 ppm for the limestone section east of

INFORMATION CIRCULAR NO. 51 23

the area. Iron and hydrogen sulfide are the most objectionable
constituents in the ground water, but they can be removed easily
and inexpensively by simple aeration.

The gravel and coarse sand in the western and northwestern
part of the area varies in depth from 22 feet to 80 feet and appears
to be the most feasible source to be developed for present muni-
cipal water supply needs. However, more detailed test drilling
and aquifer tests will be required to fully determine size, shape,
and water-bearing potential of the formation. In the future, much
larger supplies could be developed from the deeper limestone
section in Immokalee or the shallow permeable limestone to the
east.

FLORIDA GEOLOGICAL SURVEY

tially clear sand. Wells 2556-2603 and 2617-2601 are reported to
be finished in the gravel and coarse sand beds overlain by highly
organic sands and marls. Leaching of these organic zones by
downward filtering rainwater may be the cause of higher concen-
trations of sodium, potassium, and chloride in the two wells.

Table 1 and figure 10 indicate that water from all wells sam-
pled is chemically suited for domestic use, but the water in the
gravel and coarse sand beds in the western and northwestern part
of the area would require the least treatment for use as a muni-
cipal supply. However, available data are insufficient to determine
accurately the areal extent, thickness, and water-bearing charac-
teristics of these beds. If a municipal supply is to be established
in Immokalee, more detailed test drilling and aquifer tests are
needed there to determine the hydraulic characteristics of the
individual lithologic types. Because of the satisfactory quality
of the water, the shallow depth, and close proximity to the town,
the gravel and coarse sand beds appear to be the most feasible
aquifer to develop. If testing proves the beds to be too localized
and the needed quantity of water cannot be obtained, the gravel
and sand beds and the deep limestone aquifer may be utilized
as a dual source. The permeable shallow limestone to the east
can be utilized to meet future demands.

SUMMARY

Potable ground water is available throughout the Immokalee
area to a depth of about 300 feet. The subsurface materials are
primarily quartz sand, consolidated and semiconsolidated lime-
stones, marl, and shell beds, and can be considered as a single
unconfined aquifer. However, because individual layers are, for
the most part, discontinuous both vertically and horizontally,
there may be areas where the aquifer is confined and where yields
may be low.

The principal chemical constituents in the ground water are
calcium and bicarbonate. The difference in mineral composition
within the aquifer seems to be the chief reason for the difference
in quality of the water between locations. The ground water of the
sand and gravel sections in the western and northwestern part of
the Immokalee area contains from 40 to 232 ppm of dissolved
solids, as compared to 534 ppm for the limestone section east of

INFORMATION CIRCULAR NO. 51 25

REFERENCES

Bishop, E.W.
1956 Geology and ground-water resources of Highlands County,
Florida: Florida Geol. Survey Rept. Inv. 15.

Davis, J.H.
1943 The natural features of southern Florida, especially the vege-
tation and the Everglades: Florida Geol. Survey Bull. 25.

Hantush, M.C.
1956 Analysis of data from pumping tests in leaky aquifers: Am.
Geophys. Union Trans., v. 37, no. 6, p; 702-714.

Hem, J.D.
1959 Study and interpretation of the chemical characteristics of
natural water: U.S. Geol. Survey Water-Supply Paper 1473.

Klein, Howard
1962 (and others) Geology and ground-water resources of Glades and
Hendry Counties, Florida: Florida Geol. Survey Rept. Inv.
37.

Leopold, L.B.
1960 (and Langbein, W.B.), A Primer on water: U.S. Geol. Survey.

McCoy, H.J.
1962 Ground-water resources of Collier County, Florida: Florida
Geol. Survey Rept. Inv. 31.

Theis, C.V.
1938 The significance and nature of the cone of depression in
ground-water bodies: Econ. Geology, v. 33, no. 8, p. 889-902.

U.S. Public Health Service
1961 Drinking water standards: Am. Water Works Jour., v. 53, no.
8, p. 939-945.

INFORMATION CIRCULAR NO. 51

APPENDIX
Well Logs

I

INFORMATION CIRCULAR NO. 51

Well 2442-2517

Material

Sand, quartz, fine to medium, brown
Sand, quartz, fine to medium, grayish; marly
Sand, quartz, coarse, gray; phosphorite; marly
Sand, quartz, coarse, brownish gray; phosphorite;
marl increasing
Sand, quartz, medium to coarse, light gray; little
marl
Sand, quartz, fine to medium, light gray; marl in-
creasing
Sand, quartz, fine to medium, light gray; phosphorite;
little marl

Depth, in feet
below land surface

0-14
14-38
38-68

68-72

72-90

90-93

93-104

Well 2504-2558

Sand, quartz, fine to medium, buff to gray; little
marl
Sand, quartz, fine, tan
Sand, quartz, medium to coarse, tan
Gravel, quartz, well-rounded, brown to gray; some
clay
Sand, quartz, very coars e, smooth, well-rounded,
large amount of phosphorite

Well 2507-2418

Sand, quartz, medium, dark brown, organic material
Sand, quartz, medium, dark brown, organic; marly;
phosphorite in lower part
Sand, quartz, fine, light gray, marly; phosphorite in
lower part
Sand, quartz, fine, gray; becoming coarser in lower
part
Sand, quartz, fine
Sand, quartz, very fine, light gray; phosphorite
Sand, quartz, fine to medium, gray; phosphorite; clay,
bluish-green
Clay, green, phosphatic; sand, quartz, fine
Clay, green, phosphatic; sand, quartz, coarse

0-20
20-40
40-60

60-80

80-120

0-10

10-20

20-30

30-60
60-65
65-70

70-90
90-100
100-118

FLORIDA GEOLOGICAL SURVEY

Depth, in feet
Material below land surface

Well 2507-2357

Sand, quartz 0-10
Sand, calcareous, light brown, thin layer of shell
at 18 feet 10-37
Sand, quartz, medium gray 37-90
Sand, quartz, large amount of clay; greenish-gray 90-110
Sand, quartz, medium coarse, gray to green 110-163
Sand, quartz, medium gray, and clay, green 163-177
Limestone, white, sandy 177-212
Clay, sandy, calcareous, gray to green 212-290
Clay, green, phosphatic, pebble-size sand 290-303

Well 2542-2506

Sand, quartz, dark brown, organic 0-10
Sand, quartz, fine to medium, white to gray, marly,
shelly 10-18
Limestone, buff to gray, poorly consolidated; low
permeability 18-23
Sand, quartz, medium, gray, shelly 23-45
Gravel, quartz, well-rounded, smooth; some lime-
stone and clay in lower part 45-68
Sand, quartz, fine to medium, clayey 68-77
Sand, quartz, coarse, with limestone lenses 77-97
Sand, quartz, medium, with intercalated clay
lenses 97-108
Sand, quartz, coarse, highly phosphatic 108-118

Well 2556-2426

Sand, quartz, organic 0-10
Clay, bluish-green 10-15
Sand, quartz, fine, phosphatic, shelly, calcareous 15-30
Sand, quartz, fine to coarse, some grains rose
colored; phosphorite, shells, calcareous 30-45
Sand, quartz, very fine to fine, clayey at bottom 45-53
Sand, quartz, coarse, gray 53-56
Sand, quartz, fine; clay, green, becomes blue at
bottom 56-105
Sand, quartz, fine to medium; clay, bluish; shells;
phosphorite 105-120

INFORMATION CIRCULAR NO. 51 31

Depth, in feet
Material below land surface

Well 2616-2327

Sand, quartz, medium, brown, marly; organic
material 0-10
Sand, quartz, medium, light brown, shelly, marly;
becomes very shelly in lower part 10-30
Sand, quartz, very fine, gray, phosphatic 30-40
Sand, quartz, coarse, gray, clayey, phosphatic;
contains corals; sand becomes pebble-size in
lower part 40-60
Sand, quartz, very fine, light gray, phosphatic,
becomes coarser and contains dark green marl
in lower part 60-100
Sand, quartz, coarse to pebble-size; sandstone;
shell fragments; clay, marly, dark green 100-116
Sand, quartz, coarse to pebble-size; clay, marly,
green 116-140
Sand, quartz, very fine, gray, marly, clayey, phos-
phatic 140-150

Well 2627-2601

Sand, quartz, fine to medium, white to gray 0-15
Sand, quartz, fine to very coarse, well-rounded,
white, becoming finer in lower part 15-41
Sand, quartz, fine, gray, phosphatic 41-50
Sand, quartz, coarse to very coarse, white, well-
rounded, phosphatic 50-73
Gravel, quartz, white to gray, phosphatic 73-85
Sand, quartz, fine to very fine, white to pink;
clay, green-blue; marl, light brown to buff 85-95
Sand, quartz, fine, marly 95-123

FLRD GEOLOSk ( IC SUfRiW

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	Title Page
	Table of Contents
	Abstract and introduction
	Geography
	Water use
	Test-well drilling and geology
	Ground water
	Quality of water
	Summary
	References
	Appendix: Well logs