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 Geohydrology
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 Summary
 References
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FGS






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




DIVISION OF INTERIOR RESOURCES
J. V. Sollohub, Director




BUREAU OF GEOLOGY
Robert O. Vernon, Chief




Report of Investigations No. 58




SEEPAGE BENEATH HOOVER DIKE
SOUTHERN SHORE OF LAKE OKEECHOBEE, FLORIDA




By
Frederick W. Meyer


Prepared by the
UNITED STATES GEOLOGICAL


SURVEY


in cooperation with the
FLORIDA DEPARTMENT OF NATURAL RESOURCES
DIVISION OF INTERIOR RESOURCES
BUREAU OF GEOLOGY
and the
CENTRAL AND SOUTHERN FLORIDA FLOOD CONTROL DISTRICT
U. S. ARMY CORPS OF ENGINEERS


TALLAHASSEE, FLORIDA
1971









DEPARTMENT
OF
NATURAL RESOURCES




REUBIN O'D. ASKEW
Governor


RICHARD (DICK) STONE
Secretary of State




THOMAS D. O'MALLEY
Treasurer




FLOYD T. CHRISTIAN
Commissioner of Education


ROBERT L. SHEVIN
Attorney General




FRED O. DICKINSON, JR.
Comptroller




DOYLE CONNER
Commissioner ofAgriculture


W. RANDOLPH HODGES
Executive Director








LETTER OF TRANSMITTAL


Bureau of Geology
Tallahassee
May 6, 1971


Honorable Reubin O'D. Askew, Chairman
Department of Natural Resources
Tallahassee, Florida

Dear Governor Askew:

The Bureau of Geology is publishing as its Report of Investigation, a paper,
"Seepage Beneath Hoover Dike, Southern Shore of Lake Okeechobee, Florida",
written by Mr. Frederick W. Meyer, a Geophysicist of the U.S.G.S.

The needs for the future of water in Southern Florida requires that the levee of
Lake Okeechobee be increased to obtain additional storage of water for needs of
the future. This study involved determining what the rate of seepage beneath the
dike would be when the gradient was increased across the dike.

It is anticipated that toe ditches around the levee section must be constructed in
order to control the amount of water that would be permitted to seep beneath
the dikes.

Some additional pumpage back into the lake may be required utilizing the toe
ditches as sumps.

Sincerely yours,


R.O. Vernon, Chief






















































Completed manuscript received
May 6, 1971
Printed for the Florida Department of Natural Resources
Division of Interior Resources
Bureau of Geology
by Rose Printing Company
Tallahassee, Florida

Tallahassee
1971


iv










CONTENTS

Page
Abstract ............................................................ 1
Introduction ......................................................... 1
Location of investigation .............................................. 5
Purpose and scope ................................................... 5
Methods of investigation .............................................. 6
Previous studies ..................................................... 6
Acknowledgments ................................................... 7
Geographic setting ..................................................... 8
Lake Okeechobee ................................................... 8
Topography ........................................................10
Drainage .......................................................... 10
Climate ............................................................10
Geologic setting ....................................................... 12
Surface deposits .................................................... 16
Subsurface deposits .................................................. 16
Geohydrology ........................................................ 21
Site 1 ............ ... ....................... .................... 25
Description ................. .. ....................................25
Aquifers and confining beds ..........................................28
Water movement and fluctuations ..................................... 29
Quantitative Studies ..................... .......................... 37
Seepage ....................................................... 40
Site 2 ..............................................................44
Description ......................................................44
Aquifers and confining beds ......................................... 47
Water movement and fluctuations ..................................... 48
Quantitative studies ................................................ 54
Seepage ......................................................... 55
Site 3 ............................................................. 58
Description ...................................................... 58
Aquifers and confining beds .......................................... 59
Water movement and fluctuations ..................................... 62
Quantitative studies ................................................ 66
Seepage .. ....................................................... 68
Site 4 .............................................................69
Description .................................................. .... 69
Aquifers and confining beds ..................................... .... 72
Water movement and fluctuations ..................................... 73
Quantitative studies ................................................ 78
Seepage .......................................................... 79
Site 5 ......................................... ................... 80
Description ...................................................... 80
Aquifers and confining beds .................. .. .................... 83
Water movement and fluctuations ..................................... 83
Quantitative studies ................................ .............. 89
Seepage .......................................................... 90
Seepage along southern shore of Lake Okeechobee ............................ 91
Sum mary ........................................................... 92
References ...........................................................95





ILLUSTRATIONS


Page


Figure
1. Map of the Lake Okeechobee area showing locations of
investigation and test sites ........................................


2 Stage-duration curve for Lake Okeechobee showing present
and future regulation ...................................
L2. Area-capacity curves for Lake Okeechobee, 1962 ..............
3. Map of Lake Okeechobee area showing topography and
principal drainage ......................................
4. Graph showing the mean monthly rainfall and temperature,
south shore of Lake Okeechobee, 1931-60 ...................
5. Graphs showing monthly rainfall and departure from the
mean monthly rainfall; monthly mean temperature and
departure from the mean monthly temperature; south shore
of Lake Okeechobee, 1963-66 ............................
6. Map of Lake Okeechobee area showing surface deposits ........
7. Map of Lake Okeechobee area showing shallow subsurface
deposits .............................................
8. Comparison of stratigraphic columns at Fort Thompson ........
9. Map showing location of site 1 near Moore Haven .............
10. Plan and profile along line A-A' showing ..................
1 I. Selected hydraulic profiles along line A-A' showing
aquifers, confining beds, and depths of observation
wells at site I .........................................
12. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 8 at site 1; and daily and
monthly rainfall at Moore Haven, 1964-65 ...................
13. Graphs comparing water levels, chloride content, and
water temperature in wells that tap aquifer A-l at site
I with data for the lake and the L-D1 Canal, 1964-65 ..........
14- Graphs comparing water levels, chloride content,
and water temperature in wells that tap aquifer A-2
at site I with data for the lake and the L-D1 Canal,
1964-65 .............................................
15. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-3 at site 1
with data for the lake and the L-D I Canal, 1964-65 ............
16. Stage correlation curves for the L-DI Canal and Lake
Okeechobee for various drainage operations in the
Diston Island Drainage District ..........................
17. Map showing location of site 2 near Clewiston ................
18. Plan and profile along line B-B' at site 2...............
19. Selected hydraulic profiles along line B-B' showing
aquifers, confining beds, and depths of observation
wells at site 2 .......................................
20. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 7 at site 2: and daily
monthly rainfall at Clewiston; 1964-65..................


............ 4
. . . 9

............ 11

............ 13




............ 14
............ 17

............ 18
. .. ..... 20
............ 26
............ 27



............ 28



............ 31



............ 34




............ 35



............ 36



............ 38
............ 45
............ 46



............ 47



............ 50





ILLUSTRATIONS continued


Page


Figure
21. Graphs comparing water levels, chloride content, and
water temperatures in wells that tap aquifer A-1 at
site 2 with data for the lake and the L-D2 Canal,
1964-65 ............. .................................


22. Graphs comparing water levels, chloride content, and
water temperature in wells that tap confining bed
C-2 at site 2 with data for the lake and the L-D2 Canal,
1964-65 .......................................................... 52
23. Graphs comparing water levels, chloride content, and
water temperature in wells that tap aquifer A-3 at
site 2 with data for the lake and the L-D2 Canal,
1964-65 .......................................................... 53
24. Map showing location of site 3 near Lake Harbor ........................... 59
25. Plan and profile along line C-C' at site 3 .............................. 60
26. Selected hydraulic profiles along line C-C' showing
aquifers, confining beds and depths of observation
w ells at site 3 ..................... ................................. 61
27. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 2 at site 3; and daily
and monthly rainfall at Clewiston; 1964-65 ............................... 64
28. Graphs comparing water levels, chloride content, and
water temperature in wells that tap aquifer A-1 at
site 3 with data for the lake and the toe ditch,
1964-65 .......................................................... 65
29. Graphs comparing water levels, chloride content and
water temperature in wells that tap confining beds
C-1 and C-2 at site 3 with data for the lake and the
toe ditch, 1964-65 .................................................. 67
30. Map showing location of site 4 near Belle Glade ............................ 70
31. Plan and profile along line D-D' at site 4 ............................ 71
32. Selected hydraulic profiles along line D-D' showing
aquifers, confining beds and depths of observation
wells at site 4 ...................................................... 72
33. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 1 at site 4; and daily
and monthly rainfall at Belle Glade; 1964-65 .............................. 75
34. Graphs comparing water levels, chloride content,
and water temperature in wells that tap aquifer
A-i at site 4 with data for the lake, 1964-65 .............................. 76
35. Graphs comparing water levels, chloride content,
and water temperature in wells that tap aquifer A-2
at site 4 with data for the lake, 1964-65 .................................. 77
36. Map showing location of site 5 near Canal Point ............................ 81
37. Plan and profile along line E-E' at site 5 .............................. 82
38. Selected hydraulic profiles along line E-E' showing
aquifers, confining beds and depths of observation
wells at site 5 ........................................ ............ 84





ILLUSTRATIONS continued

Page

39- Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 2 at site 5; and daily
and monthly rainfall at Canal Point; 1964-65 .............................. 86
40- Graphs comparing water levels, chloride content, and
water temperature in wells that tap confining bed
C-I at site 5 with data for the lake 1964-65 ............................... 87
41. Graphs comparing water levels, chloride content, and
water temperature in wells that tap aquifer A-1 at
site 5 with data for the lake, 1964-65 ................................... 88






TABLES

Page
Table
1. Formations and their water-bearing characteristics
in the Lake Okeechobee area ........................................... 15
2. Results of slug tests at site 1 ........................................ 39
3. Results of slug tests at site 2 .......................................... 55
4. Results of slug tests at site 3 ........................................... 66
5. Results of slug tests at site 4 ......................................... 79
6. Results of seepage analyses at site 4 ..................................... 79
7. Results of slug tests at site 5 ........................................... 89
8. Results of seepage analyses at site 5 .................................... 90
9. Summary of seepage beneath the Hoover Dike along the
southern shore of Lake Okeechobee ................................... 91












SEEPAGE BENEATH HOOVER DIKE,
SOUTHERN SHORE OF
LAKE OKEECHOBEE, FLORIDA

By
Frederick W. Meyer

ABSTRACT

Future water needs in southern Florida call for an increase in the storage
capacity of Lake Okeechobee. Seepage from the lake is expected to increase as a
result of raising the lake level. Data concerning the occurrence and amounts of
seepage are needed for the design and operation of flood-control works which
will remove excess water from the rich agricultural lands along the southern
shore. Intensive studies at five sites along the southern shore of Lake
Okeechobee between the Caloosahatchee Canal and the St. Lucie Canal indicate
that seepage occurs chiefly through beds of shell and limestone which underlie
the Hoover Dike at shallow depth. Seepage rates at the five sites range from
about 0.1 to 0.9 cfs per mile per foot of head across the dike. Seepage beneath
the 50-mile length of dike should increase from about 22 to 50 cfs if the average
stage of the lake is raised from 14 to 16.5 feet. Seepage is greatest between
Moore Haven and Clewiston, where deep borrows have been excavated on the
landward and lakeward sides of the dike. Most of the seepage from the lake can
be controlled by properly spaced toe ditches which would intercept the seepage
and return it to the lake.


INTRODUCTION

With the beginning of land reclamation in the Everglades at the turn of the
century, it became evident that the key to successful utilization of the rich
organic soil lay in the control of Lake Okeechobee, figure 1. In the early 1920's
attempts at flood control were undertaken by the Everglades Drainage District
and low levees were built around the southern shore of the lake to protect
nearby towns and agricultural lands from flooding. However, the attempt proved
futile, for in 1926 and 1928 hurricanes swept waters over the levees and about
two thousand people were drowned.
In 1929, the Florida Legislature created the Okeechobee Flood Control
District which overlapped and augmented the Everglades Drainage District and
efforts were made to involve the Federal Government in providing flood
protection. With the help of President Herbert Hoover, Congress adopted the
Okeechobee project under the Rivers and Harbors Act as a navigation feature






BUREAU OF GEOLOGY


81000' 80045'


/


HENDRY COUNTY


10 MILES I 5
EXPLANATION
aM HGS (HURRICANE GATE STRUCTURE-2)
airZa HOOVER DIKE (LEVEE-DI)
0 10 MILES


Figure 1. Map of the Lake Okeechobee area showing locations of
investigation and test sites.


271I5'


27o00






REPORT OF INVESTIGATION NO. 58


with due consideration for flood control, and the U.S. Army Corps of Engineers
began work on the project in November 1930. By 1937 the Hoover Dike had
been constructed around the southern perimeter of Lake Okeechobee from
Fisheating Creek to the St. Lucie Canal.
Subsequent land reclamation in the Everglades south of Lake Okeechobee
led to overdrainage, which threatened the water supplies of the rapidly
expanding coastal cities. In 1948, Congress authorized the project "Central and
Southern Florida Project for Flood Control and Other Purposes" which, among
other things, would utilize Lake Okeechobee as a reservoir. In 1949, the State
Legislature designated the C&SFFCD (Central and Southern Florida Flood
Control District) as the agency responsible for state and local cooperation and
participation in the project. Part of the project called for increasing the storage
capacity of the lake by raising existing portions of the Hoover Dike and for
extending it around the entire shoreline. The project also called for a higher
regulation schedule for the lake.
Enlargement of the existing portions of the dike was started in 1960 and
completed in 1964. Extension of the dike around the northern perimeter is
scheduled for completion in 1970. Upon completion, the lake level (U.S. Corps
of Engineers, 1961, p.6) will be changed from that ranging between
approximately 12.5 to 15.5 feet above msl (mean sea level) to that ranging
between 15.5 and 17.5 feet above msl, figure 2. Therefore the change in
regulation would theoretically raise the average lake stage from 14 to 16.5 feet.

Seepage beneath the Hoover Dike was expected to increase as a result of
raising the lake level and agriculturists became increasingly concerned about the
effects that additional seepage would have on production in rich farmland along
the southern shore adjacent to the dike. Little was known, however, of the
existing seepage rates and the C&SFFCD and the U.S. Corps of Engineers needed
reliable data to predict the effects that raising the lake level would have on
seepage so that adequate drainage might be planned.














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10 20


30 40 50 60 70 80 90 100


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INDICATED STAGES WERE


21
EXPLANATION 2
\I REGULATION _
.. ..2C
RECORD USED-DAILY AVERAGES,
OCTOBER 1940 TO SEPTEMBER 1958
(ADAPTED FROM KENNER, 1961) 19









12 --- ---- --- --- --- --- ------------- ^

14 -- ------- --------------- ---
---- ---- -- ---- -- -- -----------------,
166




12 14



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EQUALED OR EXCEEDED


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RECENT OF TIME






REPORT OF INVESTIGATION NO. 58


LOCATION OF INVESTIGATION

The area studied is located in south central Florida along the southern
shore of Lake Okeechobee between the Caloosahatchee Canal on the west and
the St. Lucie Canal on the east (fig. 1). Intensive studies were made at the
following five sites:


Township
Site No. County (south)

1 Glades 42
2 Hendry 43
3 Palm Beach 43
4 Palm Beach 43
5 Palm Beach 41


Range
(east)


Section Levee') Station1)


33 15 D1 180+00
34 14 D2 60+18
35 36 D2 480+95
36 13 D2 980+00
37 27 D9 390+06


'U.S. Corps of Engineers base line survey.


PURPOSE AND SCOPE

In 1962, the C&SFFCD requested the U.S. Geological Survey to study the
seepage around the southern perimeter of the lake. The objective was to describe
the manner in which seepage occurred and to develop a relation between the
lake level and water levels landward of the dike, so predictions of seepage at a
lake level 2.5 feet higher than the existing level might be made.
Because the study involved about 50 miles of dike it was decided that the
estimates of seepage would be based upon detailed studies at five sites (fig. 1),
on the premise that they would be representative of the average hydraulic
conditions. The length of dike that was assumed to be represented by each site is
as follows:


Site No.

1
2
3
4


Length of Dike (miles)

9.0
8.5
8.5
10.0
14.0






BUREAU OF GEOLOGY


Field studies began in the fall of 1963 and ran concurrently with the
raising of the dike and re-routing of U.S. Highway 27 along the landward toe of
the dike between Clewiston and South Bay. As a result of the construction the
progress of the study was impeded and field work continued until the spring of
1966. During the period December 1967 through March 1968 verification tests
were performed at site 1 near Moore Haven at the request of C&SFFCD and the
U.S. Sugar Corporation. The results of those tests (Meyer, 1969) confirmed
seepage data collected during the period 1963-66.


METHODS OF INVESTIGATION

Observation wells were drilled in a line perpendicular to the dike at each
site in order to determine the extent, thickness, and character of the subsurface
materials and to define the hydraulic gradients. The wells ranged from about 4
to 50 feet deep and were constructed of either 2- or 4-inch diameter steel casing.
Measuring points were established at each observation well to reference changes
in water-levels. Fluctuations of ground-water levels on the landward side of the
Hoover Dike were continuously recorded in at least one observation well at each
of the 5 sites.
Observation points (OP's) were established in nearby canals and in the lake
to reference changes in surface-water levels. Fluctuations in the stage of Lake
Okeechobee were continuously recorded at HGS 3 (Hurricane Gate Structure 3)
at Lake Harbor and at HGS 5 at Canal Point.
Data concerning water levels, chloride content of water, and water
temperature were collected at monthly intervals. Hydrologic profiles were
constructed from these data to analyze ground-water movement (seepage)
relative to the stage of the lake. Aquifer coefficients were determined by
pumping tests, slug tests, and/or by relating seepage gains or losses in canals to
hydraulic gradients.
Wells used in this report were numbered consecutively at each site and are
cross referenced to a county numbering system and a national numbering
system. Observation points (OP's) in the lake and canals were numbered
consecutively.

PREVIOUS STUDIES

No detailed studies of seepage along the southern shore of Lake
Okeechobee were made prior to this study. However, the U.S. Corps of
Engineers (1963, p. 10) estimated that the seepage from Lake Okeechobee into
the L-DI Borrow Canal, located at site 1 near Moore Haven, would be about
12-7 cfs (cubic feet per second) per mile, per foot of head between the lake and
the canal. The Corps (1953) estimated the seepage through similar strata at four






REPORT OF INVESTIGATION NO. 58


sites along the alignments of proposed levees remote from the Hoover Dike.
Seepage for test sites 6, 7, 9, and 10 ranged from about 0.5 to 3 cfs per mile of
levee, per foot of head across the base of the proposed levees. However, the
width of the proposed levees was about half that of the Hoover Dike, therefore,
the rates of seepage under a levee equivalent in size to the Hoover Dike would be
about half the estimated rates.
Schroeder, Milliken and Love (1954, p. 12-14) reported that the
transmissivity of a sand and shell aquifer at Delray Beach, in eastern Palm Beach
County, was about 70,000 gpd/ft (gallons per day per foot). Similar aquifers
occur at shallow depth in the vicinity of Lake Okeechobee.
Parker, Ferguson, Love, and others (1955) described the geomorphology,
geology, and general hydrology of the Everglades including Lake Okeechobee.
They reported that the hydraulic conductivity(permeability) of terrace sands at
the north end of the lake ranged from 10 to 800 gpd/ft2 (gallons per day per
square foot) and might exceed 3,000 gpd/ft2 in well-sorted sand. Studies made
by the U.S. Geological Survey in cooperation with the Soil Conservation Service
indicated that there was no substantial gain or loss by the lake through
underground flow (op. cit., p. 107, 185), that the permeability of organic soils is
low (op. cit., p. 109), and that areas of low permeability generally have water of
poor quality (op. cit., p. 183-184).
Water-budget studies of Lake Okeechobee by Langbein (op. cit., p.
551-560) suggest that as much as 6 inches, or 250,000 acre-ft. could have been
lost annually, from the lake by seepage. However, Langbein concluded that the
apparent 6-inch loss was probably due to an error in the pan coefficient used in
computing evaporation.
Other studies relating to the hydrogeology of the area were made by
Greene (1966); Klein, Schroeder, and Lichtler (1964); Kenner (1961); Lichtler
(1960); Matson and Sanford (1913); Meyer and Hull (1969); Parker (1942);
Stringfield (1933); and the U.S. Corps of Engineers (1955, 1961, 1962, 1963).
Studies pertaining to the geology of the area were made by Cooke (1945); Dall
(1887, 1893); Dubar (1958); Heilprin (1887); Mansfield (1931a, 1931b, 1939);
Olsson (1964); Parker (1944); Perkins (1968); Puri and Vernon (1964); Roland
(1969); and Schroeder, Millikin, and Love (1954). Historical information on the
hydrology of the area is presented in reports by Herr (1943), Wallis (1942), and
Jones (1948).

ACKNOWLEDGMENTS

This report was prepared by the U.S. Geological Survey as part of the
cooperative water resources program with the Central and Southern Florida
Flood Control District and the U.S. Corps of Engineers. The investigation was
conducted under the direct supervision of Howard Klein, former subdistrict





BUREAU OF GEOLOGY


chief, Water Resources Division, Miami, Florida, and under the general
supervision of C.S. Conover, district chief, Water Resources Division,
Tallahassee, Florida.
The author thanks the following people for assistance rendered during the
investigation: Messrs. W. V. Storch and R. L. Taylor of the Central and Southern
Florida Flood Control District; Messrs. J. J. Koperski, O. G. Rawls, Angelo
Tabita, J. H. Grimes, and A. R. Broadfoot of the U. S. Corps of Engineers; Mr.
C. W. Knecht of the U. S. Sugar Corporation; Mr. J. D. Rogers of the Pahokee
Drainage District; Mr. W. M. Jeffries of South Florida Conservacy District; Dr. D.
R. Moore, paleontologist of the Institute of Marine Science, University of Miami;
and Dr. A A. Olsson, retired consulting geologist of Coral Gables, Florida.



GEOGRAPHIC SETTING


LAKE OKEECHOBEE


Lake Okeechobee, in the southern part of the Florida Peninsula (fig. 1), is
the second largest fresh-water lake wholly within the conterminous United
States. The lake includes parts of Glades, Hendry, Martin, Okeechobee, and Palm
Beach Counties. It is nearly circular, measuring about 35 miles from north to
south and about 30 miles from east to west. The shoreline, approximately 105
miles long, is rimmed by the Hoover Dike. The surface area of the lake, including
three small islands, is about 680 square miles (4.35 million acres) at average stage
of 14 feet above msl as shown by the area-capacity curves on figure 2A. The
average depth is 7 feet and the maximum depth is about 15 feet at average stage.
Approximately 3.5 million acre-ft (acre-feet) of fresh water are stored in the lake
at average stage 14 feet (fig. 2A). The useable storage between 10.5 and 15.5
feet is about 2 million acre-ft of which 0.6 million are used annually for
irrigation. Future water needs, however, call for increasing the storage capacity
of the lake by raising the average stage from 14 to about 16.5 feet, which will
increase both the average storage capacity and the useable storage (between 10.5
and 17.5 feet) by about a million acre-ft.
The lake water is generally hard and highly colored. The total dissolved
solids in the water seldom exceeds 300 mg/1 (milligrams per liter). The
temperature of the water ranges from 600F (160C) in the winter to about 90F
(32C) in the summer. A few municipalities and industries use the lake as a
source of water supply.
The lake is chiefly used as a flood-control storage basin for excess waters
and for irrigation of the large sugar plantations, truck farms, and cattle ranches






REPORT OF INVESTIGATION NO. 58


AREA,THOUSAND ACRES
520 480 440 400 360 320 280 240 200 160 120 80 40 0


CAPACITY, MILLION ACRE-FEET


Figure 2A. Area-capacity curves for Lake Okeechobee, 1962.








that surround the lake. It is also used for cross-state navigation, commercial
fishing, and recreation. Water from the lake also replenises supplies to the
growing coastal cities.





BUREAU OF GEOLOGY


TOPOGRAPHY

The most prominent topographic feature in southern Florida is the
Everglades-Lake Okeechobee basin (Davis, 1943, p. 41). Lake Okeechobee, which
lies at the northern extent of the basin, is a shallow saucer-like depression within
the broad flat plain. The deepest point in the lake is slightly below sea-level, fig-
ure 3. The northern half of the lake is almost completely surrounded by sandy
prairies that range in altitude from 20 to 30 feet above msl. The southern half of
the lake lies in the Everglades where the altitude of land surface ranges from 14
to 20 feet above msl.
Studies by Stephens (1951) indicated that the surface of the Everglades
agricultural area had subsided several feet due chiefly to drainage and resultant
shrinkage of organic soils. He reported (op. cit. p. 13) that during 1912-1950 the
average thickness of organic soils in the upper Evergaldes had shrunk about 40
percent, at an average rate of about one foot in ten years. Thus the altitude of
land surface in the agricultural area, prior to reclamation, was about 18 to 20
feet above msl.

DRAINAGE

Runoff from about 5,650 square miles drains southward into the lake.
Largest of the inflowing streams is the Kissimmee River (fig 3) which discharges
about 1.6 million acre-feet (0.5 cubic mile) into the lake annually. Other
principal inflowing streams or canals are Fisheating Creek, the Harney Pond and
Indian Prairie Canals, Taylor Creek, and Nubbin Slough.
The principal canals that drain the lake are the Caloosahatchee and St.
Lucie which together with the lake comprise the Okeechobee Waterway inland
navigation route between the Gulf of Mexico and the Atlantic Ocean. Other
large canals that drain the lake are the Hillsboro, North New River, West Palm
Beach, and Miami, which are also used for routing excess water during the rainy
season into the lake by back-pumping from the agricultural area.
In pristine times the natural flow from the lake was chiefly southward
through the Everglades but some flow occurred westward through the
Caloosahatchee Swamp. Parker, Ferguson, Love, and others (1955, p. 332)
estimated that overflow occurred at stage 15 feet and reached sizeable
proportions between stages 17 and 18 feet.

CLIMATE

The climate of the Lake Okeechobee region is subtropical and is
characterized by warm, humid summers and moderately cool winters.
Climatological data presented herein are based on the mean of data collected by





REPORT OF INVESTIGATION NO. 58


81000' 80045'

270-- HIGHLANDS OKEECHOBEE COUNTY ST. LUCIE
COUNT OKE HOB COUNTY





S COUNTY MARTINN
,U N T Y O U N T Y



/ PORT
27000' d KECHOBE








_0
e0




A A

















EXPLANATION
-15- CONTOUR LINE,-FEET MEAN SEA LEVEL
(U.S. CORPS OF ENGINEERS, 1958)
H EVERGLADES
zo /a -
















0 WIST MILES

Figure 3. Map of Lake Okeechobee area showing topography and principal
drainage.





BUREAU OF GEOLOGY


the U. S. Weather Bureau at Moore Haven Lock 1 and Belle Glade Experiment
Station. The average annual rainfall during 1931-1960 was 54.50 inches. Rainfall
is seasonal with about 75 percent of the yearly total occurring during May
through October. Mean monthly rainfall ranges from 1.56 inches in December to
8.46 inches in September, figure 4. The maximum daily rainfall recorded at the
Belle Glade Experiment Station was 10.90 inches in November 1931, and the
maximum monthly rainfall there was 24.11 inches in June 1945. Rainfall during
1963-65, figure 5, was below normal despite severe weather conditions that
accompanied the passage of three hurricanes. On August 27, 1964, Hurricane
Cleo passed a few miles east of Lake Okeechobee. Winds associated with Cleo
ranged from 80 mph on the east shore to 40 mph on the west shore. Rainfall
during the period August 27-28 was 1.89 inches at Belle Glade and 0.68 inch at
Moore Haven. On October 14, 1964, Hurricane Isabell, a small but wet
hurricane, passed a few miles southeast of the lake; 5.09 inches of rainfall were
measured at Belle Glade and 0.50 inch was measured at Moore Haven. On
September 8, 1965, Hurricane Betsy crossed the southern tip of Florida; and
rainfall for September 8-9 was 2.08 inches at Belle Glade and 1.99 inches at
Moore Haven.
Rainfall during 1966 was above average. Hurricane Alma skirted the west
coast of Florida during June 8-9 dumping 3.01 inches of rain at Belle Glade and
3.12 inches of rain at Moore Haven.

The average annual temperature during 1931-1960 was 72.70F. Mean
monthly temperatures ranged from 63.30F in January to 81.10F in August (fig.
5). Killing frosts occur infrequently. The lowest temperature recorded at Belle
Glade was 24F in January 1940 and the highest was 100oF in July 1931.
Temperatures were slightly below normal during 1963 and 1966 but were
slightly above normal during 1964 and 1965 (fig. 5).


GEOLOGIC SETTING

The Lake Okeechobee area lies within the Coastal Lowlands of Florida
(Cooke, 1939, p. 14). The Lake Okeechobee-Everglades basin probably was a
shallow embayment, or depression, formed on an ancient sea floor during, or
prior to, Pleistocene time. Seas covered the area during the Pleistocene
interglacial stages and marine calcareous materials were deposited. During glacial
stages the seas retreated and the area was eroded, but fresh-water marls were
deposited in shallow depressions. The Lake Okeecobee-Everglades basin
probably was a lake or a swamp during a part of each glacial stage.
The formations1 that underlie the area at shallow (less than 50 feet) depth
range from Miocene to the Holocene in age as shown in table 1. The oscillations








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TABLE 1. FORMATIONS AND THEIR WATER-BEARING CHARACTERISTICS IN THE LAKE OKEECHOBEE AREA.

Series Formation ) Range in thickness Lithology Water-bearing property
_(feet)

Holocene Organic soil 0-10 Peat. Low permeability.


Lake Flirt Marl 0-10 Sandy marl. Low permeability.
Pleistocene
Terrace deposits 0-10 Quartz sand. Low permeability.

Fort Thompson
Formation 0-30 Alternating marine and Variable permeability; low in dense
fresh-water limestones crystalline limestones and high in
and/or marls. shelly limestone.





Caloosahatchee Marl 0-30 Shell, sand, clay, and Variable permeability; high in shell
sandy limestone, beds and low in clay.




Miocene Tamiami Formation 30-110 Clay, sand, and sandy Variable permeability; high in sand-
limestone. stone beds and low in sands and clay.




1) The nomenclature and stratigraphy used herein are based on that used by the Florida Geological Survey (Puri and Vernon, 1964).





BUREAU OF GEOLOGY


of sea level are permanently recorded by alternating marine and fresh-water
strata. The shallow geology is complex due to relatively rapid depositional and
environmental changes. Consequently, few geologists agree on the ages of the
shallow formations.

The nomenclature and stratigraphy used herein are based on that used by the
Florida Geological Survey (Puri and Vernon, 1964).



SURFACE DEPOSITS

Surface deposits include organic soil, which is chiefly comprised of peat
that accumulated in the Lake Okeechobee-Everglades basin during Holocene
time, and sand of late Pleistocene-Holocene age. Figure 6 shows the type and
distribution of surface deposits in the Lake Okeechobee area. Parker, Ferguson,
Love and others (1955, p. 109) reported that samples of peat from depths
ranging from 5 to 6 feet in the upper Everglades were determined to be about
5,000 years old by Carbon 14 dating. In 1945, the organic soil ranged in
thickness from 8 feet on the southeastern side of the lake to a feather edge on
the southwestern side.
Sand that mantles the area on the north, east, and west sides of the lake is
probably part of the Pamlico Formation of late Pleistocene age. This sand,
probably not more than 10 feet thick, was derived from the higher Terrace
deposits when sea level was about 25 feet higher than present sea level. The sand
has been classified by the U. S. Soil Conservation Service as being poorly-drained
or well-drained. The well-drained sand occupies areas of slightly higher
topography suggesting that the drainage characteristic is related to topographic
position rather than to the permeability of the sand.



SUBSURFACE DEPOSITS

Underlying the surface deposits are beds of shell, clay, marl, and sand,
which range from Miocene through Pleistocene in age. These beds are referred to
herein as subsurface deposits and their distribution is shown in figure 7.
The Tamiami Formation (Parker, 1951, p. 823), of Miocene age, is
composed of silty shelly sands and silty shelly marls that occasionally contain
thin beds of limestone or sandstone. Schroeder and Klein (1954, fig. 5) reported
that the top of the formation lies at a depth of about 60 feet in the Belle Glade
area- Klein, Schroeder, and Lichtler (1964, Table 3) reported that the Tamiami
occurs at depth of about 35 feet near Moore Haven and that the formation






REPORT OF INVESTIGATION NO. 58


81000'


80045'


27 15' -


-HOOVER DIKE


/


AIKi


I


EXPLANATION
ORGANIC SOIL


3 LESS THA
E3 3-5 FEET
[I 5-8 FEET
I MORE THA
F kNE
0 WELL DRA


N 3 FEET


N 8 FEET
SAND
INED


POORLY DRAINED


260o4


DISTRICT


9IOMILES


Figure 6. Map of Lake Okeechobee area showing surface deposits.


OKEECHOBEE


27000'





BUREAU OF GEOLOGY


aood


LAKE


80045'


/OK

/

OKEECHOBEE


FORT THOMPSON N
FORMAT ON 5
F E3O O
IER DIKE CALOOSAHATCHEE
MARL :


FORMATION
CLEWISTO
.. .. ...


H.mARBOR BELEi6
................GLA DE
1' ^ -;ijliii iii ii w ^
oUNTry'. :i .:.':::i::: i|;"
OUNTYPALM BEACH CUNT

. .


AFTER PURI AND VERNON 1964, PLATE 2C
0 10 MILES
t !_


Figure 7. Map of Lake Okeechobee area showing shallow subsurface deposits.


27 15'


26 45


-





REPORT OF INVESTIGATION NO. 58


ranges from 30 to 110 feet thick. Puri and Vernon (1964, plate 2C) mapped a
small patch of green clay which occurs near the surface on the northwest side of
the lake as the Tamiami (see fig. 7). Klein, Schroeder, and Lichtler (1964, p.26),
however, included a similar bed of clay in the overlying Caloosahatchee Marl
because it seemed to be restricted to the flanks of eroded hills of the Tamiami.
During this study the top of the Tamiami Formation was located by test
drilling at a depth of about 40 feet at sites 1 and 2 near Moore Haven and
Clewiston, respectively. The Tamiami is chiefly composed of fine to very coarse
quartz sand with some limestone, sandstone, and phosphate. Principal fossils
found in the Tamiami are Balanus sp., Cymatosyrinx lunata Dall, Ringincula sp.,
Hanetia (Solenosteira) mengeana (Dall), and Nassarius (Uzita) bidentata
(Emmons). A bed of green clay occurs in the overlying Caloosahatchee Marl.
The Caloosahatchee Marl (Dall, 1887) unconformably overlies the Tamiami
Formation. The formation underlies the surface deposits in much of the area
surrounding the northeastern, northwestern, and southwestern shores of the
lake; and underlies the younger Fort Thompson Formation in the area beneath
the lake and southeastward thereof (fig. 7). The Caloosahatchee Marl is
composed chiefly of shelly sand and shelly sandy marl and an occasional bed of
limestone. DuBar (1958, p.35) assigned the Caloosahatchee to the Pleistocene
and reported a maximum thickness of about 50 feet. However, the formation
generally ranges between 15 and 30 feet thick in the study area. The fossils
contained in the formation are too numerous to list here but Cyprea problematic
is generally considered to be a good index fossil. DuBar (op. cit.) reported that
the Caloosahatchee Marl cropped out in a small area between Moore Haven and
Clewiston. The same area was mapped by Parker (1955) as Fort Thompson.
The Fort Thompson Formation (Cooke, 1929, p. 211-215) is composed of
alternating beds of fresh-water and marine marls and/or fresh-water and marine
limestone. The formation does not exceed 30 feet in thickness and underlies
most of the lake. The formation is unconformable to beds above and below. The
most common fossil in the fresh-water beds is Helisoma scalare.
After intensive studies of the type localities of the Caloosahatchee Marl
and the Fort Thompson Formation, DuBar (1958) assigned the Caloosahatchee
Marl to the Pleistocene Series rather than the Pliocene Series primarily on the
basis of vertebrate fossils, and to a lesser degree on mollusks and stratigraphic
relationship. Most investigators have accepted DuBar's biozonation but not all
agree on the age of the Caloosahatchee.
Figure 8 is a comparison of the stratigraphic columns of principal
investigators at the type locality of Fort Thompson located 21 miles west of
Moore Haven on the Caloosahatchee River. Parker (1955) presented the
stratigraphy at Fort Thompson originally proposed by Parker and Cooke (1944).
DuBar (1958) mapped the biozones along the Caloosahatchee River, subdivided
the Caloosahatchee Marl and the Fort Thompson Formation into members,












I,









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PARKER (1955) DUNAR (1965) ROOkS (196l ) OLSON (1044)






COFFEE ILL COFFEE MILL 0FFEE MILL
M C 1 "a d i
PAMLICO 7 PALICO
SAND ML




a ac
COFFEE MILL COFFEE MILL COFFEE MILL w
HAMMOCK 6 U HAMMOCK 6
S MEMBER 2 HAMMOCK I w FORMATION z
o FRESH WATER C
LIMESTONE 5 z z
5 I AND MARL m aw FORT



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A MARLUD o D EAU 3
o FRESH WATER a
h MARL AND 3 s-es
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4L AYERS LANDING ''
MARINE SHELLS 2 AYERS _A B UNIT A
_________ EE BRANCH BEE BRANCH
w o w 0
1 FORT FOR
S MARINESLLS I FR L





REPORT OF INVESTIGATION NO. 58


assigned the Fort Thompson Formation and the Caloosahatchee Marl to the
Pleistocene and included the lower part of the Fort Thompson Formation in the
Caloosahatchee Marl. Olsson (1964) assigned the Caloosahatchee Marl to upper
Miocene and assigned the lower part of the Fort Thompson to "Unit A" of
Pliocene age. Brooks (1968) included the lower part of the Fort Thompson
Formation in the Caloosahatchee Marl, reassigned the Caloosahatchee Marl to
Pliocene and lower Pleistocene, retained part of DuBar's subdivision of the
Caloosahatchee Marl and part of Parker's original Fort Thompson Formation,
and upgraded the Coffee Mill Hammock Member to a formational rank.
However, DuBar's stratigraphic designations are presently recognized and used
by the Florida Geological Survey (Puri, and Vernon 1964, p.232).
Terrace deposits, which are composed chiefly of quartz sand, underlie the
surface deposits in a band across the northernmost part of the lake (fig. 7).
These deposits are only a few feet thick and are pre-Pamlico (Pleistocene) in age.


GEOHYDROLOGY

This study is principally concerned with the source, direction and rate of
seepage through the materials underlying the Hoover Dike and to a lesser extent
with the quality of the water. Test drilling at each of the five sites yielded data
on the depth, thickness, lithology, and hydraulic characteristics of aquifers
(permeable strata) and of confining beds (relatively impermeable strata). In some
cases it was difficult to identify separate aquifers because differences in
lithologies and in permeabilities were not pronounced. However, measurements
of water levels and their fluctuations in selected observation wells yielded the
data needed to prepare hydraulic profiles (flow nets) that ultimately aided in the
identification of aquifers and confining beds and of points of recharge and
discharge.
The hydraulic profiles of the five sites were generally similar in that
seepage from the lake initially moved inland from a deep borrow (the Navigation
Canal) in the lake. Seepage moved through a filtercake, which lined the borrow,
into an aquifer (or aquifers) underlying the Hoover Dike toward discharge
points, such as canals and ditches, where water levels were controlled at
optimum levels for farming. Water-level fluctuations indicated that steady-state
flow from the lake to discharge points in the nearby agricultural areas was
usually attained within a few days after periods of unsteady water levels.
Therefore, the steady-state seepage from the lake may be reasonably estimated
by using the hydraulic gradients during periods of relatively stable water levels.

During steady-state conditions, the seepage from the lake is equivalent to
the flow through the filtercake and the flow through the aquifers beneath the
dike. At those sites where the filtercake is missing, or has about the same





BUREAU OF GEOLOGY


permeability as the continuous aquifers, the seepage from the lake is about
equivalent to the flow through the aquifers.
Obviously it would have been difficult to determine the flow through the
filtercake because of the difficulty in obtaining data from the deep borrow
(Navigation Canal) in the lake. On the other hand it was relatively easy to
determine the flow through the aquifers underlying the dike at each. site. Once
the hydraulic characteristics of the aquifer(s) and the average hydraulic gradient
in the aquifers were determined, it was possible to compute the amount of
seepage from the lake through each aquifer using the modified form of the
Darcy equation.
Q=TIL (1)

where Q is the seepage in gallons per day, T is the transmissivity of the aquifer in
gallons per day per foot, I is the average hydraulic gradient (steady state) in the
aquifer; and L is the length of dike or, canal, along which T was effective. The
gradient, I, was determined by the equation
h (2)
I=--
d
where h is the head, in feet, between the steady-state water levels, hence
equipotential lines, in two observation wells in the same aquifer, and d is the
distance, in feet, between the wells.
The hydraulic characteristics of the aquifers were determined by relating
observed water-level fluctuations caused by natural or artificial discharge and
recharge to suitable equations. The characteristics are commonly referred to as
transmissivity and hydraulic conductivity (field). Transmissivity, T, is the rate of
flow, in gallons per day, at the prevailing water temperature, through a vertical
strip of aquifer, 1 foot wide having a height equal to the saturated thickness, m,
of the aquifer, under a unit hydraulic gradient. Hydraulic conductivity (field),
Kf, is the rate of flow, in gallons per day, at the prevailing temperature, through
a one square foot section of aquifer under a unit hydraulic gradient. If T is
known, Kf may be determined by dividing T by the thickness of the aquifer (m).
Conversely, if Kf is known, T may be determined by multiplying Kf by the
thickness of the aquifer (m).
Pumping tests and slug tests were performed on selected wells in order to
determine the transmissivity of the various aquifers. The pumping test
(nonequflibrium) method involved pumping a well at a constant rate and
recording the rate of drawdown or recovery in the pumped well and/or in nearby
observation wells. The slug test (nonequilibrium) method involved injecting a
known volume of water (a slug) into an observation well and recording the rate
of decline of head in the well. The data were subsequently analyzed to
determine T using standard methods presented in reports by Ferris and others
(1962) and by Cooper, Bredehoeft, and Papadapulos (1967).





REPORT OF INVESTIGATION NO. 58


Seepage tests were also used to determine T whenever it was possible to
relate measured seepage into or out of a canal to hydraulic gradients in aquifers.
Generally, the method involved measuring the discharge entering or leaving a
specified reach of canal at the landward toe of the Hoover Dike and then relating
the discharge to ground-water gradients which were determined by water-level
measurements (equipotential lines) in the line of observation wells normal to the
dike at the respective site.
The analysis of the test data depended upon the following conditions: 1)
that the transmissivity and the gradients were uniform along the reach of the
canal affecting the seepage, and 2) that the seepage tests had continued for
sufficient time for the waters levels to stabilize, or to reach a steady state.
Under steady state conditions, the measured discharge leaving or entering
the reach of canal. Qc, is related to the seepage by the equation

Qc = Q +Qa-E (3)

where Q1 is the seepage from or into the lake, Qa is the seepage from or into the
agricultural area, and E is the loss imposed by evaporation.
Actually, none of the seepage tests continued long enough for water levels
to stabilize completely. Therefore part of the measured flow (Qc) was caused by
changes in both canal and ground-water storage. Thus compensation for change
in storage is expressed in the equation

Qc = Q + Qa + ASc + ASg E (4)
where ASc is the change in canal storage and ASg is the change in ground-water
storage; and both terms are expressed in terms of daily mean discharge. Elements
Qc Q, Qa, ASc, and ASg are positive when, 1) seepage is toward the canal,
2) discharge is leaving the reach of canal, and 3) water levels in the canal and
aquifers are falling.
The seepage tests, however, were continued sufficiently long that the
magnitude of the terms E and ASg became very small in relation to other terms
and they were dropped from the equation. Thus the following equation was used
to determine the approximate seepage relationship for a steady state condition.

Qc = Qi + Qa +ASc (5)
Equations 6 and 7 below are expressions of steady state seepage related to
the lake and agricultural area, where Ii is the hydraulic gradient related to the
lake and Ia is that related to the agricultural area.
Qr =TLI, (6)


Qa = TLIa






BUREAU OF GEOLOGY


Equation 8 below is obtained by substituting equations 6 and 7 in
equation 5; and equation 9 is obtained by solving equation 8 in terms of T.

Qc = TL(I + Ia) + ASc (8)

T =Qc- ASc (9)
L(II + la)


Usually the data collected during seepage tests were concerned with the
terms on the right hand side of equation 9. Once the transmissivity of the
aquifer (s) was determined it was possible to determine the lake seepage (Q1)
associated with hydraulic gradients beneath the Hoover Dike using equation 6.
Because a single aquifer test is merely a guidepost to aquifer transmissivity,
several tests were usually performed at each site in order to obtain values of
transmissivity that were consistent with the geologic and hydrologic setting.
Once the proper magnitude of seepage (Qi) was determined at each site it
was possible to relate the value to the hydraulic gradient across the Hoover Dike
because a linear relationship exists between the gradient across the dike and the
gradient in the aquifer(s) beneath the dike during steady-state conditions. For
convenience, seepage (Qt) is expressed in terms of a seepage factor, Se, which is
defined herein as the steady-state rate of seepage per length of recharge section
per foot of head between the recharge boundary and the discharge boundary. It
is determined by using the equation

Se = i (10)
L(h, -hc)

where Q, is the seepage rate expressed in cubic feet per second (cfs), L is the
length of the recharge section in miles, hi is the elevation of the water level at
the recharge boundary in feet, and he is the elevation of the water level at the
discharge boundary in feet.
In most cases the lakeside Navigation Canal was considered the recharge
boundary and the landside borrow canal, or toe ditch, was considered the
discharge boundary. However, in places that lacked a close, well-defined
discharge boundary on the landward side of the dike, the seepage factor was
related to the lake level and the ground-water level in an observation well located
at the landside toe of the dike. In the latter case the seepage factor was related
to the head between the lake and a specific point in the aquifer (the well); and
future estimates of seepage using the seepage factor (Se) will require a
knowledge of the steady-state water level in the well. Therefore, it would be
advantageous to retain those wells as permanent observation wells.






REPORT OF INVESTIGATION NO. 58


The value of the seepage factor for each site can be expected to decrease in
the future as the filtercake continues to form in the lakeside borrows but there
are insufficient data at present to determine the rate of reduction in the seepage
factor. However, effects of the filter-cake buildup may be determined in the
future by comparing the seepage computed using the seepage factor with the
seepage determined by gradients in aquifer(s) beneath the dike. Therefore,
long-term water-level data are needed at each site to detect future changes in
seepage factors.
Measurements of chloride content and temperature of both surface and
ground water were used to supplement the hydraulic data. The chloride content
of water in shallow aquifers beneath the southern shore of the lake is in many
places high (Parker, 1955, p. 818 and Klein, 1964, p. 73), whereas the chloride
content in lake waters is relatively low. Thus, high chloride content in aquifers
that underlie the dike would indicate that the aquifers convey relatively little
seepage from the lake; whereas low chloride content in the aquifers would
indicate that they convey significant amounts of seepage from the lake.
Temperature variations were also helpful in determining zones which convey
seepage from the lake.
Because the geohydrology at each of the sites is somewhat different, the
sites will be discussed separately in the sections that follow.

SITE 1


DESCRIPTION

Site 1 is in Glades County on the southwest shore of Lake Okeechobee
about 5 miles east of Moore Haven, as shown in figure 9. The site consists of
data collection stations along a line about 820 feet long, which constructed
normal to the Hoover Dike, as shown by figure 10. The stations consist of 19
test wells, of which 14 were used to obtain data on ground-water levels. Two
observation points (OP's) were used to obtain water-level data in the lake and in
the L-DI Canal. North of the dike is the Navigation Canal which was excavated in
the thirties to construct the Hoover Dike. South of the dike is the L-D1 Canal
which was excavated in 1962 to raise the dike to its present height (39 feet
above mean sea level) and to construct a smaller dike along the southern
(landward) bank of the L-D1 Canal.
Natural land surface at the site is about 13 feet above msl
and is underlain by about 2 to 3 feet of organic soil (see profile in fig. 10). The
area south of the LD1 Canal is devoted chiefly to agriculture (sugar cane) and
water levels there are controlled by the Diston Island Drainage District. The
district is drained by a series of north-south lateral canals (not shown in fig. 9)






BUREAU OF GEOLOGY


EXPLANATION
PROPOSED PUMP STATION
PUMP
-- CITY BOUNDARY

Figure 9. Map showing location of site 1 near Moore Haven.


about 25 feet wide and 5 feet deep. The lateral canals are spaced at half-mile
intervals and connect to main canals which are about 60 feet wide and 7 feet
deep. The main canals are equipped with pumping facilities and gated controls to
provide drainage and to route water from the lake for irrigation.
At site 1 the flow of a 3W-mile reach of the L-D1 Borrow Canal is regulated
by automatic flap gates on two 72-inch culverts (culverts 1B and 1C in fig. 9) at
the intersection with the main pump pools near culverts 1 and 1A. The flap gates
on culverts 1B and IC close when the water level in the pump pool is higher than
that in the borrow canal. The flap gates are usually closed during the rainy
season when the Diston Island Drainage District pumps into the lake. The flap






REPORT OF INVESTIGATION NO. 58


>" I EXPLANATION




I II -Il ROAD
I '; i o ig 1
I E I LL
!eso- ll-. I ie a OBSERVATIOM POINTr
I I g r .-- aIourW-WoAY LMH

-200 0 200 400
RANGE,FEET
A PLAN
4o'-
40"
HOOVER DIKE LAKE
3 FILL fine to coarse sand; and
shell.
SSOIL organic black; and some
2 DKE sand.
CL-NAL ce SILT organic black; and fine
sand.
@ LIESTONE tan, hard, sandy,
1 with some shell.
S~ SHELL tan to white, sandy,
smarly.
vEA L SAND quartz, fine to medium,
with phosphate and shell.
Q SHELL brown to gray, Ostrea sp.
i- SHELL gray to white, large and
small mollusks.
..... g SHERLL white, chiefly Turritella sp.
S CLAY green, sandy with phosphate
S- and Fontitens sp.
SSAND quarts, fine to very coarse,
3d with phosphate and mica;
and sandy limestone with
-200 6 20 0 barnacles.
RANGE,FEET
PROFILE
(STATION 180)
Figure 10. Plan and profile along line A-A' at site 1.

gates are usually open during the dry seasons when the seepage from the lake
into the L-DI Canal supplements the regulated flow of irrigation water from the
lake through culvert 1A into the district.
The profile along line A-A' at site 1 (fig. 10) shows that the materials to a
depth of about 32 feet below msl are sand, marl, shell, and limestone which
grade laterally and vertically into each other. Generally beds of limestone and
shell are considered aquifers and beds of marl, fine sand, and clay are considered
confining beds. Seepage is greatest through shell beds within the Caloosahatchee
Marl, which ranges between 10 feet above msl to 20 feet below msl.







A
JANUARY 13, 1965


.
JUNE 3,1965


C.
OCTOBER 12, 1965


SOUTH


i

















I'


ii DIKE
CONFINING BED DISCUSSED
IN TEXT BY NUMBER
rI AOUIFER DISCUSSED IN
TEXT BY NUMBER
,--2EOUIPOTENTIAL LINEVALUE IS
FEET ABOVE MEAN SEA LEVEL


==, DIRECTION OF FLOW
so- ISOCHLOR VALUE IS
MILLIGRAMS PER LITER
6 WELL NUMBER AND
UNCASED PORTION


RANGE,FEET
EXPLANATION


I>










CD
>-*g


31









a
rQ

0 0






ti






REPORT OF INVESTIGATION NO. 58


numbered consecutively with increasing depth, and the numbers are peculiar
only to site 1.
Confining bed C-1 is composed of relatively impermeable black organic
soil. The bed retards the movement of water between the surface and the
underlying beds, but its confining ability is locally ineffective where the bed is
cut by many canals and ditches. Aquifer A-1 is chiefly a sandy marly limestone.
The upper surface of the bed is well cemented and relatively impermeable,
however, locally occurring solution holes account for zones of high permeability,
Confining bed C-2 is composed of shelly sand. The bed is only slightly less
permeable than the overlying aquifer but it probably contains zones of very low
permeability. Aquifer A-2 is chiefly shell and is highly permeable. Confining bed
C-3 is composed of green clay and it is relatively impermeable. Aquifer A-3 is
composed of sand and sandstone and it is moderately permeable.
Some seepage occurs through all the beds but most seepage occurs through
aquifers A-i, A-2, and A-3. However, aquifers A-i and A-2 and perhaps
confining bed C-2 are the chief sources of seepage from the lake because they are
breached by deep borrow canals on the lakeward and landward sides of the dike.
The Navigation Canal is the perennial recharge boundary. The L-DI Canal is the
chief dry season discharge boundary and the network of ditches in the fields
nearby is the chief wet season discharge boundary.
Silt deposits that line the sides and bottoms of the borrow canals play an
important part in seepage. These deposits were formed chiefly by the settling of
the fine fractions from the excavated material and by the accumulation of
organic sediments derived from dead vegetation and the erosion of nearby
surface materials. Because the level of the lake is usually higher than the water
level in the Diston Island Drainage District, hydrostatic pressure has probably
caused these deposits to form a filtercake on the bottom and walls of the
Navigation Canal; and the buildup of the filtercake probably has caused a
progressive reduction in the rate of seepage from the lake over the years. The
loss in head across the filtercake is an important factor in analyzing aquifer
coefficients because more head is required to move water at a given rate through
the filtercake than to move water at the same rate through a like thickness of
aquifer. Therefore, the determination of seepage through an aquifer must be
related to the transmissivity and hydraulic gradients within the aquifer itself, and
not to gradients which include the head across the filtercake.

WATER MOVEMENT AND FLUCTUATIONS

The principal direction of water movement at site 1 is from Lake
Okeechobee to the Diston Island Drainage District as shown in the hydraulic
profiles (fig. 11) by the arrows representing flow lines. Short seasonal reversals
occur however when the stage of the lake is routinely lowered prior to the rainy






30 BUREAU OF GEOLOGY


season. Profiles A-C were constructed from data collected on January 13, 1965,
June 3, 1965, and October 12, 1965, respectively, to show the distribution of
equipotential lines and chloride content for selected high and low stages of the
lake. Although the profiles depict the instantaneous conditions of flow normal
to the Hoover Dike, that is, along a stream line, the equipotential lines generally
represent the steady state hydraulic gradients in the flow system.
On January 13, 1965, a period of high water levels, the stage of Lake
Okeechobee at the Navigation Canal was 14.18 feet and the stage of the L-DI
Canal was 11.69 feet. The principal direction of water movement in aquifers A-i
and A-2 was from the Navigation Canal to the L-DI Canal. The principal
direction of water movement in aquifer A-3 was southward toward an
undetermined point of discharge in the Diston Island Drainage District, but some
upward movement probably occurred through confining bed C-3.in the area
immediately south of the L-DI Canal. Most of the seepage occurred through
aquifers A-i and A-2. Of the measured 10.5 cfs discharging through culvert 1C
from the 3-.mile reach of the L-D1 Canal, about 7.5 cfs was estimated to have
seeped from the lake. The close, even spacing of equipotential lines and the low
chloride content in aquifers A-1 and A-2 beneath the Hoover Dike suggests that
locally the upper 25 to 30 feet of strata act as a unit aquifer. The high chloride
content in water in aquifer A-3 suggested that relatively little water seeped from
the lake through that unit.
On June 3, 1965, a period of low water levels, the stage of Lake
Okeechobee at the Navigation Canal was 12.44 feet, the stage of the L-D1 Canal
was 12.09 feet, and the principal direction of ground-water movement in
aquifers A-I, A-2, and A-3 was from the Navigation Canal into the Diston Island
Drainage District. No losses occurred from the L-DI Canal other than seepage
and evaporation. Hydraulic gradients were low indicating that the rate of seepage
was lower than it was on January 13, 1965.
On October 12, 1965, a period of high water level, the stage of Lake
Okeechobee at the Navigation Canal was 14.37 feet and the stage of the L-D1
Canal was 1432 feet. About 8.5 cfs was flowing from the lake through culvert 1
into the 3%-mile reach of the LD1 Canal because of a malfunction of culvert 1B
after the passing of Hurricane Betsy in September. This condition caused a
landward shift in the principal recharge boundary from the Navigation Canal to
the L-DI Canal, which resulted in a significant decrease in the chloride content in
aquifer waters beneath the L-DI Canal.
A comparison of the daily mean stage of the lake with the daily highest
water level in well 8, on figure 12, shows that during 1964-65 the stage of the
lake was higher than the stage of the water level in well 8 except for a few days
in June 1965. Fluctuations of the lake level are chiefly caused by seiche, winds,
seasonal rainfall on the basin, and water-management practices of the nearby
drainage districts and the U. S. Corps of Engineers. Fluctuations of the water








REPORT OF INVESTIGATION NO. 58


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J F M A M J J A S O N D


( HURRICANE
) HURRICANE
( HURRICANE


EXPLANATION

CLEO C
ISABELL (
BETSY


IRRIGATION EFFECT
PUMPING EFFECT


Figure 12. Graphs showing daily stages of Lake Okeechobee and ground-
water levels in well 8 at site 1; and daily and monthly rainfall at
Moore Haven, 1964-65.


level in well 8 are chiefly caused by fluctuations of the water level in the L-DI
Canal which is presently controlled by the water-management practices of the
Diston Island Drainage District.

Water-level fluctuations in the lake that generally lasted only a few days
were usually caused by winds. In some instances short-term peaks (waves), such
as those caused by hurricanes or low waves from large boats, were transmitted


4 255 480 061 067 234 520 476 889 346 274 065 072

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BUREAU OF GEOLOGY


through aquifer A-I and were recorded in well 8. The location of well 8 is such
that its water level is closely related to the water level in the LD1 Borrow Canal.
The water level in the L-DI Canal is controlled by two 6-foot gated culverts (1B
and IC) which connect to the pump bays at culverts 1 and 1A (see locations on
fig. 9). The water levels in the pump bays are in turn controlled by gates on
culverts 1 and 1A, which lead to the lake, and by rectangular concrete controls
with removable stop logs, which lead from the pump bays to the main canals of
the Diston Island Drainage District.
When the district needs water from the lake for irrigation during dry
periods, the gates on culverts 1 and 1A are partly opened and the stop logs in the
controls are removed, thereby allowing water to flow from the lake into the
district. This operation causes the automatic flap gates in culverts 1B and 1C to
open, allowing water to drain from the L-D1 Canal into the pump bays until the
level in the L-DI Canal reaches a level slightly above that in the pump bays, or
until the level in the L-DI Canal falls below the bottom invert of culverts 1B and
IC (invert elevation 10.2 feet).
When the district needs to remove excess water from the fields after heavy
rains the stop logs are replaced in the controls, the gates on culverts 1 and 1A are
opened, and water is pumped from the main canals into the lake. This operation
causes the water levels in the pump bays to exceed that in the L-D Canal,
thereby closing the automatic flap gates in culverts 1B and 1C. Then the water
level in the L-DI Canal rises to a static level between the lake level and the water
level in the district.
Thus, the peaks on the hydrograph of well 8 (fig. 12) during 1964 usually
represented periods when the district was pumping excess water into the lake
and the troughs usually represented periods when the district was withdrawing
irrigation water from the lake.
During April and May, 1965, the U. S. Corps of Engineers routinely
lowered the stage of Lake Okeechobee and the regional water level to about 12
feet above msl prior to the wet season (fig. 12). After heavy rains in early June,
water levels in the district rose above the lake level and reverse seepage, that is
seepage from the district to the lake, occurred for a few days. After a normal
landward gradient was reestablished, the gates on culverts 1B and 1C were closed
due to pumping from the district to the lake and the water levels in well 8 (and
in the L-DI Canal) rose to a level between the lake level and the water level in the
district.
On September 11, 1965, shortly after the passing of Hurricane Betsy,
some debris became lodged under the automatic flap gate at culvert 1B,
permitting water to flow from the lake through culvert 1 (which was open) and
culvert IB into the L-D1 Canal, and the water level in well 8 (and in the LD1
Canal) approached that of the lake (fig. 12). If no water was seeping from the
-DI Canal into the district, then the water levels in the L-D1 Canal and well 8






REPORT OF INVESTIGATION NO. 58


would have equalled that of the lakes and the flow into the L-D1 Canal would
have ceased. However, the water level in well 8 (and in the L-D1 Canal) was lower
than the lake level. Therefore, it follows that water was seeping from the L-D1
Canal into the district and the flow through culvert 1B represented the seepage
losses along the 3-mile reach from culvert 1B to culvert 1C, assuming that
evaporation losses were insignificant. This condition existed through December,
1965, and the inland shift in the distribution of flow is shown by the hydraulic
profile on October 12, 1965, in figure 11. Thus operations of the landside
drainage works in the Diston Island Drainage District has a significant effect on
the relationships between the stage of the lake and the stage of the L-D1 Canal,
the hydraulic gradients from the lake, and the seepage from the lake.
Figures 13 through 15 are graphs comparing water levels, chloride content,
and water temperature in wells that tap the three aquifers with data for the lake
and the L-D1 Canal. The lines representing the well data are coded by numbers
of dots; the line with the least dots represents the well nearest the lake.
A comparison of the data in figures 13 and 14 suggest that locally aquifers
A-1 and A-2 are hydraulically connected and function as a unit aquifer. The data
in figure 15 suggest that confing bed C-3 separates aquifer A-3 from the
shallower aquifers. The data in figures 13 and 14 also indicate that near the dike
water levels in aquifers A-1 and A-2 are highly influenced by the operational
stage of the L-D1 Canal. Of particular importance is the fact that most of the time
the water levels in the wells 5, 10, and 11 were closely related to fluctuations in
the water levels in the LD1 Canal despite their close proximity to the recharge
boundary (the Navigation Canal). This relationship suggest that the head loss
between the lake and the water levels in the nearby wells is caused by a layer of
silt, or a filtercake, on the walls of the lakeside Navigation Canal.
Generally, waters in the lake, the L-Dl Canal, and in aquifers A-1 and A-2,
contained chloride concentrations ranging between 50 and 100 mg/1 (milligrams
per liter) as shown on figures 13 and 14. Chloride content was slightly lower in
the wells farthest from the lake suggesting that aquifers A-1 and A-2 were
recharged by local rainfall as well as by seepage from the lake.
Waters in aquifer A-3 (fig. 15) contained chloride concentrations ranging
from 100 to more than 800 mg/1. Concentrations in aquifer A-3 were lowest in
the area near the Navigation Canal where infiltration of fresh water from the
lake was greatest. Concentrations were highest in the district south of the L-DI
Canal, which suggests that seepage through aquifer A-3 from the lake into the
district is of minor importance.
However, infiltration from the L-DI Canal into aquifer A-3 was induced by
pumping nearby well 14 (fig 15). The chloride content in well 3 decreased from
about 800 mg/1 in February 1965 to 500 mg/1 in April 1965 after well 14 was
pumped at a rate of about 80 gpm (gallons per minute) on March 4. In August
1965, well 14 was again pumped and the water in well 3 was freshened to about







BUREAU OF GEOLOGY


M J J A S N DIJ F M A M J JA S 0 N D
1964 EXPLANATION 1965


-LAKE -- WELL 8


L-DI CANAL
---WELL 5


-..- WELL 6
---- WELL 12


Figure 13. Graphs comparing water levels, chloride content and water
temperature in wells that tap aquifer A-1 at site 1 with data for
the lake and the D1 Canal, 1964-65.


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REPORT OF INVESTIGATION NO. 58


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SI I I I I


JFMAMJ JASONDJF MAMJJAS ND
1964 19.65
EXPLANATION


- LAKE
-- L-DI CANAL
-- WELL 10


---- WELL 7
WELL 9
-...- WELL 13


Figure 14. Graphs comparing water levels, chloride content and water
temperature in wells that tap aquifer A-2 at site 1 with data for
the lake and the L-Di Canal, 1964-65.


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1964 1965
EXPLANATION


- L-DI CANAL
---LAKE
--- WELL II


Figure 15. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-3 at site 1 with data for
the lake and the L-D1 Canal, 1964-65.


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REPORT OF INVESTIGATION NO. 58


500 mg/1. Well 3 was further freshened to less than 300 mg/1 after the
malfunction of culvert 1B during Hurrican Betsy in September 1965, which
caused the recharge boundary to shift from the Navigation Canal to the L-DI
Canal.
The temperature (OF) of water in the L-D1 Canal and in the lake side
Navigation Canal ranged from the high sixties during the winter to high eighties
during the summer. The seasonal variation in temperature of ground water
decreased with depth. Temperatures in aquifer A-3 were least affected by
seasonal variations in temperature.
During 1964-65, monthly observations of water levels and of operations of
the drainage works at site 1 suggested that three generalized relations could be
recognized between the stages of the lake and the L-D1 Canal. Monthly
measurements of the stages in the lake were plotted against the stages in the L-D1
Canal, figure 16, and the plots were then related to the physical operations of the
drainage works. The first line (1) represents the relationship caused by the
malfunction of culvert 1B and the resultant shift in the recharge boundary from
the Navigation Canal to the L-Dl Canal. The second line (2) represents the
approximate relationship that occurs when the L-DI Canal is ponded by
pumping operations. The third line (3) represents the relationship when the L-D1
Canal is draining into the Diston Island Drainage District during irrigation
operations. Because seepage from the lake is closely related to the head between
the lake and the L-D1 Canal, the relationship in line 2 can be used to estimate
water levels in the L-DI Canal when the canal is ponded by operations of the
drainage works during wet periods if no physical changes occur in the system.

QUANTITATIVE STUDIES

Aquifer tests were performed at site 1 to determine the transmissivity (T)
and/or the hydraulic conductivity (K) of the aquifers which are the chief
conveyers of seepage from the lake. Pumping tests were conducted on wells 9
and 10 which tap aquifer A-2, and on well 3 which taps aquifer A-3 (see
locations of wells on profile in fig. 11A).
Well 9 was pumped for 60 minutes at a rate of 90 gpm while water-level
fluctuations were recorded in wells 3, 6, 7, 10, 13, and in the pumped well (9).
Well 10 was pumped for 40 minutes at a rate of 122 gpm while fluctuations of
water levels were recorded in wells 5, 7, 8, and 11. The data indicated that
recharge from the L-DI Canal, from the Navigation Canal and from vertical
leakage, caused me arawdowns in the observation wells to be suppressed early in
the tests. However, an analysis of a few data which were collected early in the
tests and therefore least affected by recharge, suggests that the value of T could
be in the magnitude of 100,000 gpd/ft. The tests also indicated that locally beds
A-i, C-2 are essentially a unit aquifer, that water flows from the borrow canals







BUREAU OF GEOLOGY


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Drainage District.





into the aquifers A-1 and A-2, and that some leakage (minor amounts) occurs
through bed C-3.

Well 3 was pumped for 62 minutes at a rate of 12% gpm while fluctuations
of water levels were recorded in wells 11 and 14, and in the pumped well. The


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REPORT OF INVESTIGATION NO. 58 39


data suggest that the transmissivity of aquifer A-3 in about 7,000 gpd/ft and that
some leakage occurs through confining end C-3.
Slug tests were conducted in wells 1 through 3 at 9 different zones during
drilling operations. The results of the slug tests are presented in table 2. The
analysis of the slug tests generally required a great deal of subjective judgement,
therefore the results only suggest the magnitude of values that might be
expected. The estimated value of T for the saturated zone of flow beneath the
dike between 13.5 feet above msl and 17 feet below msl is about 28,500 gpd/ft;
and that for the zone between 17 and 31 feet below msl is about 6,900 gpd/ft.
Probably the minimum T value that might be expected for the total flow zone
would be about 35,000 gpd/ft.


TABLE 2. RESULTS OF SLUG TESTS AT SITE 1.
Thickness Kf T
Bed (feet) (gpd/ft2) (gpd/ft)

Dike Fill 31 20 60
C-1 1 2 2
A-1 '5 1,2001 6,0002
C-2 3 70 210
A-2 18.5 1,200 22,200
C-3 6 20 120
A-3 8 850 6,800
TOTAL 44.5 35,392

1 Saturated
2 Estimated

On January 13, 1965 a seepage test was conducted in the 3-mile reach of
the L-D1 Canal between culverts 1B and 1C (see location on fig. 9). Water levels
were measured in the observation wells and at observation points at site 1 in
order to relate hydraulic gradients to the measured discharge (10.5 cfs) flowing
eastward from the L-DI Canal through culvert 1 C. The waterlevel data were used
to construct the hydraulic profile at site 1 (see profile A in figure 11) and the
hydraulic gradients at site 1 were assumed to be uniform along the L-DI Canal
from culvert 1B to culvert 1C. Culvert 1B was closed, so that the flow through
culvert 1C represented most of the seepage from the lake to the LDI Canal.
Seepage from the lake was assumed to have reached a steady-state condition
because the water level in well 8 (thus the stage of the L-D1 Canal) had
stabilized for a period of at least 2 weeks prior to the test (fig. 12). The






BUREAU OF GEOLOGY


transmissitivity along the 3Wmile reach was assumed to be uniform because
geologic conditions along the reach (U. S. Corps of Engineers 1961, plate 13) are
similar to those at site 1, therefore, the hydraulic gradient between wells 10 and
7 was assumed to be representative of the gradient across the aquifer beneath the
Hoover Dike along the reach. The hydraulic gradient, Ii, between wells 10 and 7
was determined by equation 2.

h 0.71 foot
11 = 0.00355
d 200 feet

The hydraulic gradient across the aquifer from the L-DI Canal southward to the
Diston Island Drainage District was almost flat at site 1, therefore the I was
assumed to be zero.
Transmissivity, T, was computed using equation 9.

QeP -ASp
T =L (11 a)
where Qc was the measured discharge from the L-DI Canal at culvert 1C, 10.5 cfs
(6.8 mgd); ASc was determined to be equivalent to 1.7 cfs (1.1 mgd); L was
18,800 feet; I was 0.00355; and Ia was assumed to be an insignificant factor.

6.8 mgd- 1.1 mgd
T 18,800 ft (0.00355) + 18,800 ft (0.00000)

T = 85,400 gpd/ft

Thus, the transmissivity of the strata that convey the seepage from the
lake was estimated to be about 85,400 gpd/ft; and the value of T obtained by
the seepage test was considered to be more representative of the actual T than
those obtained by the pumping tests and the slug tests.
In 1968, however, three additional seepage tests were conducted at site 1
at the request of the C&SFFCD in order to verify the results of the January 13th
test. Test 3 (Meyer, 1969, p. 20-26) involved the lowering of the water level in
the 3Wmile reach of the L-D1 Canal several feet below the lake level by
pumping; and the results of test 3 suggested that the transmissivity of the
water-bearing strata beneath the dike was about 64,600 gpd/ft. However, the
results of the three tests indicated that T is probably about 72,300 gpd/ft (op.
cit., p. 27); therefore, the value 72,300 gpd/ft was used to compute seepage at
site 1.
SEEPAGE

Seepage from the lake at site 1 can be estimated using the transmissivity of
the water-bearing strata that underlie the dike and the hydraulic gradient






REPORT OF INVESTIGATION NO. 58


between wells 10 and 7. On the other hand, it would be more convenient to
estimate the seepage using the water levels in the lake and the L-D1 Canal, but
the loss in head across the filtercake on the walls of the Navigation Canal
prevents a direct computation of seepage from the lake (Q1) using equations 6
or 9, and the aquifer transmissivity. However, a comparison of water-level data
indicated that there is a direct relationship between the water levels in wells 10
and 7 and the water levels in the lake and the L-D1 Canal. Therefore, the seepage
through the aquifer(s) can be related directly to the head between the lake and
the LD1 Canal by using equation 10, assuming that the relationships will not
change appreciably in the future due to the slow buildup of the filtercake.
The seepage factor, Se, was therefore computed using equation 10 and the
data for the seepage test on January 13, 1965. The length of canal section (L)
was 18,800 feet, or 3.56 miles; the seepage pickup (Q1) was assumed to be 8.8
cfs; the stage of the lake (hi) was 14.18 feet; and the stage of the L-D1 Canal
(hc) was 11.69 feet.

Q1 8.8 cfs
L(hi hc) 3.56 mi. (14.18 ft. 11.69 ft.)

= 1.0 cfs/mi/ft


Thus, the seepage factor, Se, at site 1 was estimated to be about 1.0 cfs per mile
per foot of head between the lake and the L-D1 Canal; and this value was
considered representative for design purposes.
On the basis of the 1968 tests, the seepage for the test on January 13,
1965, was re-evaluated using. 72,300 gpd/ft as the value of T. Equation 9 was
used to evaluate the gradients related to the seepage into the L-D1 Canal.

72,300 gpdft= 6.8 mgd 1.1 mgd
72,300 gpd/ft 18,800 ft. (0.00355 + Ia)

la = 0.00064
The result suggested that some seepage was derived from the Diston Island
Drainage District. Equation 7 was used to determine the amount that seeped
from the district into the L-DI Canal.

Qa = 72,300 gpd/ft x 0.00064 x 18,800 ft.

= 0.87 mgd or 1.3 cfs

Thus the earlier assumption that the gradient Ia on the south side of the canal
was equal to zero was erroneous, and a net 1.3 cfs seeped from the district into






BUREAU OF GEOLOGY


the L-DI Canal along the 3V2-mile reach. This condition was later confirmed by
test 2 of the 1968 tests.
On the basis of the 1968 value of T, the distribution of seepage during the
test on January 13, 1965, was re-evaluated using equation 5.

Qc= Q +Qa+ASc
10.5 cfs = 7.5 cfs + 1.3 cfs + 1.7 cfs
10.5 cfs = 10.5 cfs

Thus, the seepage from the lake (Q1) was about 7.5 cfs and not 8.8 cfs as
originally determined.
The seepage factor (Se) was recomputed using equation 10, where Q1 is
7.5 cfs, L is 3.56 miles, he (lake) is 14.18 feet, and he (L-D1 Canal) is 11.69 feet.

Qi
L (h -hc)

Se =7.5 cfs
3.56 mi (14.18 ft. 11.69 ft.)

Se = 0.8 cfs/mi/ft.


Thus the seepage factor (Se) for the January 13, 1965 test is about 0.8 cfs per
mile per foot of head between the stage of the lake and that of the L-D1 Canal;
and the results of the January 13 test are within the order of magnitude of both
the original estimate which was used for design purposes and the average value of
0.9 cfs/mi/ft which was determined by the 1968 tests. However, the 1968 value
is considered the more reliable of the three values. Therefore, the seepage factor
(Se) at site 1 is about 0.9 cfs per mile per foot of head between the stage of Lake
Okeechobee and that of the L-DI Canal.
The present effect of the filtercake in the Navigation Canal is included in
the value of the seepage factor but the value can be expected to decrease as the
filtercake continues to build up and the lake level is raised. The data suggest that
the filtercake causes a 68 percent reduction in seepage from the lake. If the
filtercake has formed uniformly since the excavation of the Navigation Canal in
the early thirties then the buildup of the filtercake has reduced the seepage
about 2 percent per year, however, there are no data to support this conclusion.
Therefore no attempt was made to relate the seepage factor to future changes in
the filtercake, but it is apparent that the value of the seepage factor will decrease
in the future.
Seepage from the lake into the Diston Island Drainage District is related to
the lake level and the operational water levels of the district and the L-D1 Canal.






REPORT OF INVESTIGATION NO. 58


If the average stage in the LD1 Canal were maintained at, or slightly below, the
average stage of water table in the Diston Island Drainage District then the L-D1
Canal would intercept most of the seepage from the lake. For example, if the
average stage of the L-D1 Canal were maintained at about 11.0 feet (that is below
the average stage in the district).by pumping the seepage back into the lake, then
the average annual rate of seepage into the L-D1 Canal would be the product of
the seepage factor (0.9 cfs/mi/ft) and the average head between the lake and the
L-D1 Canal (14 ft. 11 ft. = 3 ft), or 2.7 cfs per mile. If the average stage of the
lake were raised to 16.5 feet then the average rate of seepage into the L-DI Canal
would be about 5.0 cfs per mile. If the L-D1 Canal were ponded, that is, closed
off at both ends, then the seepage would pass from the lake through the canal
southward into the Diston Island Drainage District; and the seepage would be
approximately proportional to the head between the lake and the L-D1 Canal.
For example, if the culverts at the ends of the L-D1 Canal were closed so that the
canal were ponded, then the stage of the canal that would correspond to an
average lake stage of 14 feet would be about 12.8 feet (from line 2 in figure 16);
and the corresponding average rate of seepage into the Diston Island Drainage
District would be about 1.1 cfs per mile (1.2 ft x 0.9 cfs/mi/ft). If the average
stage of the lake were increased to 16.5 feet then the average stage of the L-D1
Canal would be 14.1 feet and the average seepage to the Diston Island Drainage
District would be about 2.2 cfs per mile.

In order to estimate the average increase in seepage that would result from
raising the average stage of the lake from 14 to 16.5 feet, one would have to
know the long-term water levels in the L-DI Canal and in the District. The only
data available, however, were those collected during 1964-65, but they suggest
that the long-term water levels in the L-D1 Canal and the adjacent fields are
regulated slightly below 11.5 feet during the dry (irrigation) season, and that the
aforementioned water levels are regulated slightly above 12 feet during the wet
season. If it is assumed that the future regulation of the water levels will be the
same, that is, drainage operations will occur 50 percent of the time and irrigation
operations will occur the other 50 percent, then it is possible to estimate the
increase in seepage that will result from raising the average stage of the lake.

During the 1964 dry season, most of the seepage from the lake was
intercepted by the L-D1 Canal, which discharged the seepage southward into the
Diston Island Drainage District. The water level in the L-D1 Canal was controlled
at a stage of about 11.5 feet by the irrigation practices of the Diston Island
Drainage District regardless of the stage in the lake. Therefore, during irrigation
periods; the long-term average head between the lake and the L-D1 Canal is
estimated to be about 2.5 feet (14 ft 11.5 ft = 2.5 ft) and the resultant seepage
is about 2.2 cfs per mile (2.5 ft x 0.9 cfs/mi/ft). If the average stage of the lake is
raised to 16.5 feet, the average head should be about 5.0 feet and the resultant
seepage should be about 4.5 cfs per mile.






BUREAU OF GEOLOGY


During the 1964 wet season, the drainage practices of the Diston Island
Drainage District usually caused the water in the L-D1 Canal to pond. When the
average stage of the lake is 14 feet, the average stage of the L-DI Canal is about
12.8 feet. Therefore, during the wet seasons the long-term average gradient
between the lake and the L-D1 Canal is estimated to be about 1.2 feet and the
resultant seepage is about 1.1 cfs per mile. If the average stage of the lake is
raised to 16.5 feet, then the average stage of the L-DI Canal will rise to 14.1 feet
and the average seepage will be about 2.2. cfs per mile. If the irrigation and
drainage seasons are about equal in duration, then the average annual seepage
rates are about 1.6 and 3.4 cfs per mile for the corresponding average lake stages
of 14 and 16.5 feet and the average increase in seepage will be about 1.8 cfs per
mile.
Thus, raising the average stage of Lake Okeechobee from 14 feet to 16.5
feet should increase the average seepage rate at site from 1.6 to 3.4 cfs per mile;
and the seepage beneath the 9-mile section of dike represented by site 1 should
increase from 14.4 to 30.6 cfs.

SITE 2

DESCRIPTION

Site 2 is located in Hendry County on the southwestern shore of Lake
Okeechobee about 1 mile east of Clewiston as shown on Figure 17. The site
consists of data-collection stations along a line about 470 feet long, which was
constructed normal to the Hoover Dike, as shown in plain view of figure 18. The
data-collection stations include 16 test wells, of which 11 were used to obtain
data on ground-water levels, and two observation points (OP's) which were used
to obtain data on water-levels in the lake and in the LD2 Canal.

North of the Hoover Dike is the Navigation Canal which was used in the
early thirties for borrow to construct the dike. South of the Hoover Dike is the
L-D2 Canal from which borrow was taken in 1962 to raise the dike to its present
height. The L-D2 Canal is about 9,700 feet long and is not connected to the
flood control works in the agricultural area or to the Industrial Canal at
Clewiston, just south of the L-D2 Canal on U.S. Highway 27 which parallels the
length of the canal. Beyond U. S. Highway 27 the land is locally uncultivated
and poorly drained. The nearest controlled drainage at site 2 is located in the
agricultural area about one quarter mile south of the dike. Canals in the
agricultural area, which are equipped with pumping facilities and gated controls,
provide drainage during wet periods and route water from the lake for irrigation
during dry periods. Water levels in the agricultural area are locally regulated by
the Clewiston Drainage District.








REPORT OF INVESTIGATION NO. 58


EXPLANATION
PROPOSED PUMP STATION
PUMP
--- CITY BOUNDARY


Figure 17. Map showing location of site 2 near Clewiston.


Natural land surface at site 2 ranges from 14 to 15 feet above msl and it is
underlain by about a foot of organic soil (see profile in fig. 18). Beneath the soil
are beds of sand, limestone, marl, clay, and shell which grade vertically and
laterally into each other. Generally beds of shell and limestone are permeable
and beds of organic soil, sand, marl and clay are relatively impermeable. Seepage
is probably greatest through solution holes in the limestone which ranges from 4
to 12 feet (above msl) in what appears to be the upper part of the







BUREAU OF GEOLOGY


PLAN


t


o


z
?tt:
caQ


RANGE,FEET


0 200 400
RANGE, FEET
PROFILE
(STATION 60+18)


EXPLANATION

o WELL
S OBSERVATION POINT
RIGHT-OF-WAY LINE
= ROAD
B-B' LINE OF PROFILE




3 FILL fine quartz sand and shell
SSOIL organic black; and some
sand.
[j SILT organic black; and fine
sand.
[] SAND quartz, medium to fine;
with some shells.
g LIMESTONE white to light
gray, hard to soft,
very sandy, with some
shell and phosphate.
SMARL white to light gray,
very sandy.
[] SAND quartz, very fine to
very coarse, with some
fine phosphate.
U SHELL white to tan, sandy,
mostly micromollusks.
SCLAY green, sandy, shelly,
with phosphate.
j SANDSTONE grading into sandy
limestone.
E SAND quartz fine to very
coarse.


Figure 18. Plan and profile along line B-B' at site 2.



Caloosahatchee Marl. Permeable beds of shell, which range from 8 to 27 feet
below msl in the lower part of what also appears to be Caloosahatchee Marl, are
potential conveyers of large amounts of seepage if penetrated by deep borrow
canals on the landward and lakeward sides of the dike.






REPORT OF INVESTIGATION NO. 58


AQUIFERS AND CONFINING BEDS


The aquifers, confining
B-B' at site 2, are shown on


beds, and depths of observation wells along line
figure 19A. The aquifers and confining beds are


A.
JANUARY 14, 1965
B
40'i


B.
JUNE 3, 1965


C.
OCTOBER 12, 1965


RANGE, FEET
EXPLANATION
4= DIRECTION OF FLOW


i CONFINING BED DISCUSSED
SIN TEXT BY NUMBER

Si AQUIFER DISCUSSED IN
1i TEXT BY NUMBER


SISOCHLOR VALUE IS
MILLIGRAMS PER LITER
I WELL NUMBER AND
UNCASED PORTION


_.EQUIPOTENTIAL LINE,VALUE IS
FEET ABOVE MEAN SEA LEVEL





Figure 19. Selected hydraulic profiles along line B-B' showing aquifers,
confining beds and depths of observation wells at site 2.


SDIKE






BUREAU OF GEOLOGY


numbered consecutively with increasing depth and the unit numbers are peculiar
only to site 2.
Confining bed C-l is 2 to 3 feet thick and it is composed of a bed of sandy
organic soil and a bed of medium to fine quartz sand. Aquifer A-1 ranges from 2
to 7 feet in thickness and it is a hard, sandy, limestone that locally contains
solution holes. Confining bed C-2 is about 17 feet thick beneath the center of
the dike and the thickness of the bed increases southward. The upper 3 feet is
composed of clayey sandy marl and the lower 14-feet is composed of fine to
coarse quartz sand. Aquifer A-2 is about 2 feet thick and is chiefly shell.
Confining bed C-3 is about 2 feet thick and consists of sandy green clay that
grades vertically into the shell in aquifers A-2 and A-3. Aquifer A-2 and
confining bed C-3 dip southward from the lake toward the agricultural area. On
the other hand aquifer A-3 is a wedge-shaped bed of shell that appeasf to
increase in thickness northward beneath the lake. Aquifer A-3 is about 10 feet
thick beneath the center of the dike and the shell is similar to that in aquifer
A-2. The upper part of aquifer A-3 contains clay and the lower part contains
sandy limestone. Confining bed C-4 is about 2 feet thick and it is composed
chiefly of fine to coarse quartz sand. Aquifer A-4 is more than 4 feet thick and
it is composed of sandy limestone.
Some seepage occurs through each bed that underlies the dike but seepage
is greatest through aquifer A-1 which has been breached by borrow canals.
Aquifers A-2, A-3, and A-4 are permeable but they are overlain by at least 10
feet of "tight" sand which retards the movement of water from the Navigation
Canal into the aquifers, therefore, seepage through aquifers A-2, A-3, and A-4 is
considered to be a relatively unimportant factor in the analysis. Silt deposits that
line the bottom and sides of the borrow canals at site 2 are also considered to be
relatively unimportant factors in determining seepage because the data indicate
that the loss in head across the deposits is relatively small. The principal recharge
boundary for the upper 30 feet of strata-that underlies the dike is the Navigation
Canal and the principal discharge boundary is the network of drainage canals
located one-quarter mile south of the dike in the agricultural area. The recharge
and discharge boundaries for the deeper strata are undermined.


WATER MOVEMENT AND FLUCTUATIONS

The principal direction of seepage at site 2 is southward from the lake
toward the drainage works in the agricultural area. Short reversals occur seasonally,
however, when the stage of the lake is routinely lowered by the Corps of
Engineers prior to the rainy season, or when heavy rains cause water levels in the
agricultural area to abruptly rise above, the lake level during the wet season.
Hydraulic profiles for January 14, 1965, June 3, 1965, and October 12, 1965
were constructed to show the direction of flow and the distribution of






REPORT OF INVESTIGATION NO. 58


equipotential lines (water levels) and isochlors for selected high and low stages of
the lake (fig. 19).
On January 14, 1965, a period of high water levels, the stage of Lake
Okeechobee at site 2 was 14.29 feet and the stage of the L-D2 Canal was 13.53
feet. Seepage through aquifers A-1 and A-2, and through confining bed C-2, was
southward from the lake toward the agricultural area. The low chloride content
and inferred steep hydraulic gradients in aquifers A-1 and A-2, and in confining
bed C-2, suggest that most of the seepage occurred there. The high chloride
content and the inferred low hydraulic gradient in aquifer A-3 (and perhaps A-4)
suggest that it conveys insignificant amounts of seepage. Water levels in bed A-3
were lower than those in bed A-2 indicating that bed C-3 retards the vertical
movement of water between overlying and underlying beds.

On June 3, 1965, a period of low water levels, the stage of the lake was
12.44 feet and the stage of the L-D2 Canal was 11.94 feet. The equipotential
lines show that seepage through aquifers A-1 and A-2, and confining bed C-2,
was southward from the Navigation Canal to the L-D2 Canal and to the
agricultural area. Hydraulic gradients in aquifer A-3 (and perhaps A-4) was low
therefore water movement there was probably insignificant. The slight lakeward
shift in chloride content in aquifer A-3 suggest that water movement there was
northward.

On October 12, 1965, a period of high water levels, the stage of the lake
was 14.54 feet and the stage of the L-D2 Canal was 14.20 feet. The data were
collected during a period of slightly unsteady water-level conditions which were
caused by locally occurring rains and strong winds. Water movement in aquifers
A-1 and A-2 and confining bed C-2, was southward from the lake toward the
agricultural area. The equipotential lines in aquifer A-1 infer a low hydraulic
gradient from the lake toward the agricultural area. The equipotential lines in
bed C-2 suggests that the permeability of bed C-2 is lower than bed A-1. The
curvature of the lines suggests that some water moved downward through bed
C-2 from the Navigation Canal and the L-D2 Canal and some water moved
upward through bed C-2 from aquifer A-2. A lakeward shift in chloride content
and hydraulic gradient in aquifer A-3 suggest that water movement there was
northward from the agricultural area toward the lake.

Figure 20 is a graph comparing the daily mean stage of the lake with the
daily highest water level in well 7 which taps aquifer A-i and is located on the
landward berm of the Hoover Dike (see location on figure 18). The water level in
well 7 is about the same as that in the L-D2 Canal. During 1964-65, the lake
level was generally higher than the water level in well 7 except during April
through June 1964, June through August 1965, and September 1965, when
heavy rains caused local water levels south of the dike to rise higher and faster
than the level of the lake.






BUREAU OF GEOLOGY


16


15

14

13

12


_j
I.->
biug
,La U1

tru
lu
-4n
4L
CbLk
l&LI





C
4

-Jc
I @


2.83 5.96 5.07 4.53 3.72




I III L I I 1I 11. -111 .1 .


3.74




I Ii


0.37


0.92


J F M A M J J A S O N D




1965













CLEWIST*N US ENG


J F M A M


J J A S O


Figure 20. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in wel 7 at site 2; and daily and monthly
rainfall at Cewiston; 1964-65.


Generally the water level in well 7 rose in response to local rainfall and to
corresponding fluctuations of the lake. However, when the stage of the lake was
below 13.5 feet, fluctuations of the water level in well 7 were chiefly caused by
local rainfall. Short-term fluctuations of the lake level had relatively little affect
on the water level in the well, which suggested that the hydraulic connection
(the permeability of the aquifer) between well 7 and the lake is poor. The water
level in wel 7 appears to be only slightly affected by drainage because the
drainage works (network of canals) are relatively far from the well and the
hydraulic connection is relatively poor. The water-level recession during April
and May 1965 was caused by the routine lowering of regional water levels by the
Corps of Engineers prior to the wet season.


2.11 2.46 1 L21 5.48

3 -CLEWISTON US ENG
2


0


(n14
-j
I.- IA
IS-




001
cc



5
-'4
13
UC


z


0


DAILY MEAN LAKE STAGE 16
DAILY HIGH GROUND WATER STAGE AT -WELL 7
LAND SURFACE DATUM AT WELL
14.11 FEET. MEAN SEA LEVEL







REPORT OF INVESTIGATION NO. 58 51



Figures 21 through 23 are graphs comparing water levels, chloride content,

and water temperature in wells that tap selected aquifers and confining beds


M J J A S ON DJ F M A M J J
1964 1965

EXPLANATION


- LAKE
L-D2 CANAL
---WELL 4


---- WELL 7
--- WELL 10


Figure 21. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-i at site 2 with data for
the lake and the L-D2 Canal, 1964-65.


-J
W
W
-J

-1



W

w
w

w
3-o


I-

U.


200

-I~







J
oJr
-J

M


W
wI
LLF M
uZ
W


WL

w W
W
03

W
aD


I I


I-


W W 1 I w w II ll fr


-----


-


V


I I


I I





































































1964 1965


EXPLANATION


- LAKE
- L-D2 CANAL


--- WELL 3
-*.- WELL 8


Figure 22. Graphs comparing water levels, chloride content, and water
temperature in wells that tap confining bed C-2 at site 2 with
data for the lake and the L-D2 Canal, 1964-65.


BUREAU OF GEOLOGY


-J

-1
tL



tuJ
ui







ta
u-









-S




C2




I-W
a-









W


a
0



US
a






REPORT OF INVESTIGATION NO. 58


. J
w




W 14



00 -
Ito











l i.
> Z





c 2







gs ooLAKE i W E LL
i,, I ".






t o i >\/
LLW L


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-U.1



















u ,., 90 -
Io -
400I






















1964 1965
-- LAKE WELL 2
WELL I















_FM A8 M JASON OJ FMAMJ JASON 0


L-D2 CANAL WELL II





BUREAU OF GEOLOGY


with data for the lake and the L-D2 Canal. The lines representing well data are
coded by a number of dots. The line with the least dots represents the well
nearest to the lake.
Water levels nearest the lake in aquifer A-i are closely related to the lake
level (fig. 21). This relationship indicates that the permeability of aquifer A-1 is
about the same as the permeability of the filtercakein the Navigation Canal. The
hydraulic gradient, which is shown by water levels.in the line of wells, indicates
that water moved southward from the lake. through the L-D2 Canal toward the
agricultural area. Chloride content in water in well 4, which is nearest the lake, is
closely related to that of the lake. The lag in time between peak chloride content
in the lake and peak chloride content in the L-D2 Canal suggest that seepage
through the aquifer occurs at a slow rate. For example, the peak chloride -
concentration in the lake water occurred in April 1965 while the peak chloride
concentration in the L-D2 Canal occurred about 2 months later. Chloride
content in the landward wells and the L-D2 Canal was lower than that in the
lake, suggesting that some dilution by local recharge (rainfall) occurs there. The
temperature of the water in aquifer A-i, in the lake, and in the L-D2 Canal varies
seasonally, and the range in temperature of ground water is less than that of the
surface water but the data suggest that there is a general relation between water
movement and temperature in the lake and in aquifer A-1.
Water levels in confining bed C-2 near the lake are also closely related to
the water level in the lake (fig. 22). The similarity between the graphs in figures
21 and 22 suggest that the permeabilities of aquifer A-1 and confining bed C-2
are probably similar.
Water levels in aquifer A-3 are closely related to the water level in the
L-D2 Canal (fig. 23). The hydraulic gradient, which is inferred from the
differences between the water levels in the wells, is low, therefore the rate of
water movement in aquifer A-3 is probably slow even if the permeability of the
material is relatively high. Chloride content is highest in the water in wells which
are the deepest and farthest from the lake suggesting that seepage through A-3 is
relatively insignificant. The decrease in the chloride content in well 2 during
1964 and 1965 was probably caused by the movement of fresh water into the
aquifer from the Navigation Canal after well 2 and other nearby wells in aquifer
A-3 were pumped during sampling. The high chloride content and occasional
reverse gradient in aquifer A-3 suggest that aquifer A-3 is unimportant in the
analysis of seepage from the lake. The temperature of the water in aquifer A-3
fluctuates through a relatively narrow range and the data suggest that there is
slight relationship between water movement and temperature in aquifer A-3.

QUANTITATIVE STUDIES

Aquifer tests were performed at site 2 to determine the transmissivity (T)
and/or the hydraulic conductivity (Kf) of the beds which are the chief conveyors
of seepage from the lake.






REPORT OF INVESTIGATION NO. 58 55


A pumping test was conducted on well 2 which taps aquifer A-3. The well
was pumped for 74 minutes.at a rate of 75 gpm and water level fluctuations
were recorded in wells 1 and 11, and in the pumped well. Data from the test
indicated that recharge suppressed the drawdown in the observation wells early
in the test, therefore, it was not possible to accurately determine the
transmissivity of aquifer A-3. A few early data, however, suggested that the T of
aquifer A-3 does not exceed 70,000 gpd/ft, but the transmissivity obtained by
the slug tests was considered to be in the correct order of magnitude for aquifer
A-3. Slug tests were performed in wells 1 through 4, 7, 10, and 11 in order to
determine the magnitude of the hydraulic conductivities of various beds beneath
the dike. The results of the test are shown in table 3.

TABLE 3. RESULTS OF SLUG TESTS AT SITE 2.
Thickness1 K T
Bed (feet) (gpd/ft2) (gpd/ft)
Dike Fill 1 1002 1002
C-1 2 1002 2002
A-1 8 384 3,040
C-2 17 50 850
A-2 2 2,0002 4,0002
C-3 2 (1 (1
A-3 10 1,340 13,400

Total 42 21,590



Measured below center of dike
2Estimated

No data were obtained in confining bed C-3 and in aquifer A-4, but the seepage
there is considered to be a minor factor in the total analysis. The total
transmissivity of the 42-foot section beneath the center of the dike is about
22,000 gpd/ft. However, the distribution of hydraulic gradients in the various
beds is not uniform, therefore seepage should be computed for each bed.

SEEPAGE

Seepage from the lake at site 2 can be estimated best by determining the
flow through the 42 feet of saturated material down to confining bed C-4
underlying the dike rather than the flow through the filtercake in the Navigation
Canal. The flow through the materials for a given period can be determined from






BUREAU OF GEOLOGY


the transmissivities of the individual beds and the hydraulic gradients within the
beds. If the flow through the materials is steady state and the hydraulic gradients
in the aquifer are directly related to the hydraulic gradient across the dike, that
is, between the Navigation Canal and the L-D2 Canal, then the seepage through
the materials can be related to the long-term head across the dike. A comparison
of water levels in wells at various depths in the materials suggest that a direct
relationship between the hydraulic gradients does in fact exist. Therefore, the
flow, hence the seepage, beneath the dike was computed for January 14, 1965, a
period of steady-state water levels and above average lake levels (see profile A in
fig. 19) and the seepage from the lake was related to the head across the dike by
the seepage factor Se.
Seepage on January 14, 1965 is related to the transmissivities which were
presented in table 3 of the proceeding section, and to the hydraulic gradients in
the hydraulic profile in figure 19. The seepage through the upper 28 feet of the
materials was computed using equation 1, where T is the sum of the
transmissivities of the dike fill (saturated part), confining bed C-l, aquifer A-l,
and confining bed C-2; and I was the hydraulic gradient in aquifer A-1.

Q= TIL
= 4,190 gpd/ft x 0.00292 x 1 ft.
= 12.2 gpd per foot of width of aquifer

Seepage through 2-foot thick aquifer A-2 (fig. 19) was computed using
equation 1 where T is the transmissivity of aquifer A-2 and I was the hydraulic
gradient in aquifer A-2.

Q = TIL
= 4,000 gpd/ft x 0.0014 x 1 ft.
= 4.6 gpd per foot of width of aquifer

Seepage through 2-foot thick bed C-3 was very low and was therefore omitted in
the analysis. Seepage through the 12-foot thick aquifer A-3 was computed using
equation 1 where T is the transmissivity of aquifer A-3 and I was the hydraulic
gradient in aquifer A-3.

Q= TIL
= 13,400 gpd/ft x 0.00014 x 1 ft.
= 1.9 gpd per foot of width of aquifer

Seepage through the basal materials shown in figure 19, confining bed C-4
and aquifer A-4, was considered an insignificant factor in the analysis. Thus, the
seepage from the lake through the saturated material (42 ft deep) is equal to the
sum of the computed seepages.






-REPORT OF INVESTIGATION NO. 58


Q1 = 12.2 gpd +4.6 gpd + 1.9 gpd
= 18.7 gpd per foot of width of aquifer

However, the geologic section prepared by the Corps of Engineers (1961, plate
16) indicates that aquifer A-i, which is the chief source of seepage at site 2, is
discontinuous along the dike, therefore the seepage at site 2 is probably higher
than the average value along the section of dike assigned to site 2. However, the
seepage at site 2 is believed to be within the correct order of magnitude and is
therefore assumed to be representative of that along 8% miles of dike.
On the basis of the steady-state seepage from the lake on January 14,
1965, the seepage factor (Se) at site 2 was determined using equation 10 where
Q1 is the January 14 seepage through a one-foot wide segment of the aquifer
materials L is 1/5,280 mile, h was the stage of the lake, and hi was the stage of
the L-D2 Canal.

Q1
e L(hI -hc)

18.7 gpd/ft x 5280 ft
1 mi (14.29 ft 13.53 ft)

= 129,900 gpd/mi/ft, or about 0.2 cfs/mi/ft.

Thus the seepage factor (Se) at site 2 is about 0.2 cfs/mi/ft, which includes the
retarding effect of the filtercake in the Navigation Canal. However, the effect of
the filtercake at site 2, though small compared to that at site 1, will probably
cause a further reduction in seepage as the filtercake continues to form and the
lake is raised.
A comparison of water-level measurements in the lake with those in the
L-D2 Canal during 1964-65 suggested that the rate of seepage varied with the
stage of the, lake and stage of the LD2 Canal. Under normal conditions, the head
across the dike was about 0.5 foot when the stage of the lake was at or below 14
feet, and the head was about 0.75 foot when the stage of the lake was about 14
feet.
When the stage of the lake was below 14 feet, the stage of the LID2 Canal
was greatly affected by local rainfall which ran off the dike and U.S. Highway 27
and accumulated in the canal. However, during the longer dry periods, the
steady seepage from the lake caused a constant head relationship (about 0.5
foot) to exist between the lake and the canal. Therefore the maximum seepage
rate that might be expected when the average stage of the lake is 14 feet would
be about (0.2 cfs/mi/ft x 0.5 ft) 0.1 cfs per mile.
When the stage of the lake is between 14 and 15 feet, the water level in the
L-D2 Canal rises above its banks, but overland flow from the canal is prevented





BUREAU OF GEOLOGY


by U.S. Highway 27 which parallels the southern side of the canal and by fill at
the terminuses of the canal. If the relationship between the lake and the L-D2
Canal remains the same for higher stages of the lake and no changes occur in
drainage, then the average stage of the L-D2 Canal would be about 15.75 feet if
the average stage of the lake is raised to 16.5 feet, and seepage from the lake
would be about (0.2 cfs/mi/ft x 0.75 ft) 0.15 cfs per mile. However, if the LD2
Canal were connected to a drain and controlled at a constant stage of 11.5 feet
then the seepage from the lake beneath the dike would be about 0.5 cfs/mi when
the average stage of the lake was 14 feet and about 1.0 cfs/mi when the average
stage was 16.5 feet.
Thus seepage from the lake at site 2 should increase about 0.05 cfs per
mile, if the average stage of the lake is raised from 14 to 16.5 feet, the L-D2
Canal remains isolated from the drainage canals, and the prevailing drainage
conditions south of the dike do not change. The seepage beneath the 8%-mile
segment of dike represented by site 2 therefore would increase from about 0.8
cfs to about 13 cfs if the average stage of the lake were raised from 14 to 16.5
feet.

SITE 3

DESCRIPTION

Site 3, shown in figure 24, is in Palm Beach County on the southern shore
of Lake Okeechobee about 0.6 mile east of Lake Harbor.
The site consists of data-collection stations along a line about 860 feet long
which was constructed normal to the Hoover Dike, as shown in figure 25. The
stations include 11 test wells of which 6 were used to obtain data on
ground-water levels, and two observation points which were used to obtain data
on water levels in the lake and in the landside toe ditch.
North of the Hoover Dike is the Navigation Canal which was excavated in
the early thirties for borrow to construct the dike. In 1964, the north side of the
Navigation Canal was deepened for borrow which was used to raise the dike to
its present height and for borrow which was used in constructing the roadbed for
U.S. Highway 27. South of the dike is a toe ditch which was excavated in 1965
by the South Shore Drainage District to intercept seepage from the lake and to
route excess water from the agricultural area south of the highway westward
into the Miami Canal where it is pumped into the lake by the C&SFFCD.

Natural land surface at the site ranges from 13 to 14 feet above msl and is
underlain by 6 to 8 feet of soft black organic soil. Beneath the soil are beds of
clay, limestone and sand which grade vertically and laterally into each other.
Generally the beds of shell and limestone are permeable and comprise aquifers;
and beds of sand, clay, and organic soil are less premeable and comprise






REPORT OF INVESTIGATION NO. 58


EXPLANATION
PUMP STATION
PUMP
o I MILES



Figure 24. Map showing location of site 3 near Lake Harbor.


confining beds. Seepage is greatest through the beds of limestone and shell which
range from 4 feet above to 13 feet below msl in the Caloosahatchee Marl.

AQUIFERS AND CONFINING BEDS

The aquifers, confining beds and depths of observation wells along line
C-C' at site 3 are shown on profile A in figure 26. The aquifers and confining
beds are numbered consecutively with increasing depth from land surface and
the numbers are peculiar only to site 3.
Confining bed C-1 ranges from 6 to 8 feet in thickness and consists of
relatively impermeable organic soil. Confining bed C-2 is about 3 feet thick and
consists of relatively impermeable beds of soft shelly marl and hard fresh-water
limestone. Aquifer A-1 ranges from 14 to 17 feet in thickness and consists of
soft to hard, permeable beds of shell and limestone that locally contain zones of






BUREAU OF GEOLOGY


Io47 II


=I0=4 \$ -4 i s. I ---
z o ===

_V C C'
-200 0 200 400 600
RANGE,FEET
PLAN


RANGE,FEET
PROFILE
(STATION 480 + 95)


EXPLANATION
WELL
OBSERVATION POINT
RIGHT-OF-WAY LINE
ROAD
LINE OF PROFILE









FILL fine quartz sand, shell,
and limestone fragments.
SOIL organic black; and some
sand.
SILT organic black, sandy.
CLAY brown to gray, with many
Helisoma sp.; grades into
hard shelly limestone.
LIMESTONE tan to white, hard to
soft, with many Rangia sp.
SAND quartz, fine, with many
Rangia sp. and Helisoma sp.
SHELL gray to white, soft to
hard, with Macona sp.
Cardium sp. and Pecten sp.
LIMESTONE gray to tan, hard,
porous shelly.
SAND quartz, fine.
SAND quartz, medium to fine,
with some shell.


Figure 25. Plan and profile along line C-C' at site 3.




sand. Confining bed C-3 is at least 10 feet thick and consists of fine sand which
is low in permeability. Most of the seepage occurs through aquifer A-i, although
some seepage occurs through each bed.

The silt deposits, or the filtercake, that lined walls of the Navigation Canal
were partly removed from the north side of the canal when it was deepened for
borrow in 1964. The removal of these deposits probably caused seepage to
increase; however, the slow redeposition of the silt should cause a reduction in
future seepage.








JANUARY 14, 1965


NORTH


SOUTH


-200 0 200 400 600 -200 0 200 400 600
RANGE, FEET
EXPLANATION
== DIRECTION OF FLOW


CONFINING BED DISCUSSED
IN TEXT BY NUMBER
AQUIFER DISCUSSED IN
TEXT BY NUMBER


_., ISOCHLOR VALUE IS
MILLIGRAMS PER LITER
I WELL NUMBER AND
UNCASED PORTION


-EQUIPOTENTIAL LINE,VALUE IS 0 FILL
FEET ABOVE MEAN SEA LEVEL


Figure 26. Selected hydraulic profiles along line C-C' showing aquifers, confining beds, and depths of observation wells at site 3.


E@ DIKE


JUNE 3,1965


MAY 18,1966







BUREAU OF GEOLOGY


WATER MOVEMENT AND FLUCTUATIONS

The principal direction of water movement at site 3 is southward from the
lake to the agricultural area. Hydraulic profiles A through C in figure 26 were
constructed to show the distribution of equipotentials and isochlors, and the
principal direction of water movement on January 14, 1965, June 3, 1965 and
May 18, 1966, respectively.
On January 14, 1965, a time of high water levels, the stage of the
Navigation Canal was 14.37 feet and the stage of the water table at the southern
toe of the dike was 12.06 feet. Seepage was chiefly southward through aquifer
A-1 toward the drainage canals in the agricultural area. (see profile A in fig. 26).
The chloride content of the water in aquifer A-1 was low near the lake and
relatively high in the confining beds, a condition that indicates water movement
is greater through aquifer A-1.
During February 1965, a drainage ditch was excavated into bed C-2 along
the toe of the dike from a culvert, which underlies U.S. Highway 27 near site 3,
to the Miami Canal; and another drainage ditch was excavated from the south
side of the culvert southward into the agricultural area and westward along the
south side of the highway (see profile B in fig. 26). A pump was installed at the
west end of the dike toe ditch to pump excess water from the agricultural area
south of the highway into the Miami Canal near HGS-3 at Lake Harbor.
On June 3, 1965, a time of low water levels, the stage of the Navigation
Canal was 12.42 feet and the pumping level in the toe ditch was 8.88 feet.
Seepage was southward through aquifer A-1 from the lake toward the
agricultural area, but most of the seepage was upward into the toe ditch (see
profile B in fig. 26). Water from the agricultural area and seepage was flowing
westward in the ditch to the pump which was operating at the west end of the
toe ditch. The drawdown in the ditch caused water levels in wells at site 3 to
decline, which indicated that the hydraulic gradient and seepage from the lake
had increased. However, the high chloride content of the ditch water (380 mg/1)
indicated that only a small part of the water pumped from the ditch could have
originated as seepage from the lake because the chloride content of the lake
water was only 70 mg/l.
During December 1965 the toe ditch was deepened so that the bottom of
the ditch penetrated the upper part of aquifer A-1. On May 18, 1966, a seepage
test was conducted at site 3 and the water-level data shown in profile C, figure
26, was related to the measured seepage in the toe ditch. The pumping level in
the ditch was 7.44 feet (msl) and the stage of the lake was 13.75 feet. The
closely spaced equipotential lines beneath the dike indicate that the principal
direction and rate of water movement was southward from the lake through
aquifer A-1 to the toe ditch. South of the highway, water movement in aquifer
A-1 was northward toward the toe ditch. However, the hydraulic gradient there






REPORT OF INVESTIGATION NO. 58


was lower than that beneath the dike indicating that some of the pickup, or
seepage, into the toe ditch came from the agricultural area. The seepage through
confining beds C-1 and C-2 was considered an insignificant factor in the test.
During 1964, water levels in the area south of the dike were chiefly
affected by dewatering operations during the construction of U.S. Highway 27,
as shown by the hydrograph of well 2 on figure 27. During February 1965, a toe
ditch was excavated along the southern toe of the dike and linked to the
drainage system in the fields on the south side of U.S. Highway 27. During the
remainder of 1965, the water level in well 2, located a few feet north of the toe
ditch, was largely affected by drainage operations of the agricultural area and the
stage never exceeded 12 feet. Prior to excavation of the toe ditch, the water level
in the aquifer at the toe of the dike probably ranged from 12.0 to 12.5 feet, or
about the same as the range in stage of the water level in well 2 during December
1964 through January 1965.
Figures 28 and 29 are graphs comparing water levels, chloride content, and
water temperatures in the lake and the toe ditch and in wells that tap aquifer
A-1 and confining beds C-1 and C-2. The lines representing well data are coded
by dots and the line with the least dots represents the well closest to the lake
while the line with the most dots represents the well farthest from the lake.
Graphs of water levels, chloride content, and temperature in wells that tap
aquifer A-i are compared with those in the Navigation Canal and in the toe ditch
during 1964-65 in figure 28. Water levels were highest in the well nearest the
lake and lowest in the well nearest the agricultural area, thereby indicating that
seepage was at all times southward from the lake. During 1964 water levels in
the wells were lowered by dewatering operations during the construction of U.S.
Highway 27 and by the drainage operations in the agricultural area. During 1965
the drawdown in the toe ditch lowered water levels in the observation wells,
indicating that the toe ditch had intercepted some of the seepage from the
lake. A comparison of chloride content in the wells in aquifer A-1 with the
chloride content in the lake suggests that aquifer A-i is the principal conveyor of
seepage from the lake because the concentrations are about equal. A comparison
of the chloride content in the wells with the chloride content in the toe ditch
suggests that most of the water that is pumped from the agricultural area is
derived from an inland source which is high in chloride content. A comparison
of chloride peaks in the lake and chloride peaks in the ditch (fig. 28) suggests
that variations in the quality of the lake at site 3 are partly caused by brackish
ground water which is pumped from the agricultural area through the Miami
Canal into the lake during wet periods. A comparison of the temperature data
shows that ground-water temperatures in wells 3 and 6 lag the temperature of
the lake by several months, indicating that the movement of water through the
aquifer is at best slow.
Water levels, chloride content, and temperatures in confining beds C-1 and
C-2 are compared graphically with those in the toe ditch and the lake in figure





64 BUREAU OF GEOLOGY




1 -
S1964

4 14













LAND SURFACE DATUM AT WELLS
S- C EWI US1











J F M A M J J A S 0 N D
31 I -- I














>5
o














J F M A M J J A S O N D
I0 --























ground-water levels in we. l 2 at site 3; and daily a 2d monthly
in t Clewton; 1964-65.
10 -A "





611965







REPORT OF INVESTIGATION NO.58


- LAKE
- TOE DITCH
-'- WELL 3


EXPLANATION


--.- WELL 4
----WELL S


tl q Io- i
1 I I I I I




J FMA M JJ A S O N J FMAM JJ ASOND
1964 9s5



Figure 28. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-1 at site 3 with data for
the lake and the toe-ditch, 1964-65.





66 BUREAU OF GEOLOGY


29. The water level in well 5 (taps bed C-l) south of the highway is directly
affected by the drawdown in the nearby toe ditch. The drawdown in well 1
(near the lake in bed C-2), is caused indirectly by the drawdown in aquifer A-1.
A comparison of the chloride content in well 1 with the other chloride
data in figure 29 suggests that the uniformly high chloride content in well 1 is an
indication that seepage from the lake through the filtercake and confining beds
is very slow. The time lag between the peak temperature in the lake and the peak
temperature in well 1 also suggests that the rate of seepage through bed C-2 from
the lake is slow.
A comparison of the chloride content in wells 4 and 5 (fig. 29) with the
chloride content in wells 3, 4 and 6 (fig. 28) shows that the water in beds C-1 -
and C-2 contain slightly higher concentrations of chloride than bed A-l,
therefore the high chloride content in the surface water (in canals and ditches)
that is pumped from the agricultural area could be caused by the local flushing
of brackish ground water from beds C-1 and C-2, or by flushing of residual
brackish ground water from aquifer A-1 in an area considerably distant from the
lake.
QUANTITATIVE STUDIES
Tests were performed at site 3 to determine the transmissivities of the beds
which are the chief conveyors of seepage from the lake. A pumping test was
conducted on well 4, which taps aquifer A-1. Well 4 was pumped for 62 minutes
at a rate of 30 gpm and the water level fluctuations were measured in wells 1, 2,
and 6, and in the pumped well (4). The data indicated that recharge from the
Navigation Canal and the ditches south of the dike suppressed the drawdowns in
the observation wells early in the test. However a few early data suggested that
the T of aquifer A-I is about 16,000 gpd/ft. No effects of pumping were
observed in the nearby shallow wells suggesting that the permeabilities of
confining beds C-1 and C-2 are low.
Slug tests conducted in the wells 1 through 7, suggested that the
transmissivity of aquifer A-1 is about 18,000 gpd/ft., and the transmissivities of
confining beds C-1 and C-2 are about 20 gpd/ft. and 200 gpd/ft respectively
(table 4).

TABLE 4 RESULTS OF SLUG TESTS TEST AT SITE 3.

Thickness Kf T
Bed (feet) (gpd/ft2) (gpd/ft)

C-I 7 3 21
C-2 2.5 82 206


15 1,200


18,000








REPORT OF INVESTIGATION NO. 58


V EXPLANATION

1964

,I I I I I I I I I I I I I I I I I -- LAKE I
TOE DITCH

























1I iI i' I I i i I IW Ii I I
1965
---WE I (BED C-2}
----WELL 5 (BEDC-I)


































J FMA MJJ A SON J FMAM J JASON o




Figure 29. Graphs comparing water levels, chloride content, and water
temperature in wells that tap confining beds C-1 and C-2 at site
3 with data for the lake and the toe ditch, 1964-65.


'VV
S90
5 SO
IIW
s- o
CL
a
t 0

u1t
Q -


I J'n_





BUREAU OF GEOLOGY


A seepage test was conducted on May 18, 1966 at site 3 in a 1,000-foot
reach of the toe ditch which parallels the dike (see profile C in fig. 26). Pumping
from the ditch was of sufficient duration that water levels approached steady
state. About 0.2 cfs of seepage was measured in the 1,000-foot reach. The shape
of hydraulic profile at site 3 during the seepage test indicates that the ditch was
receiving seepage from both the lake and the agricultural area. The hydraulic
gradients indicated that most of the seepage was from the lake. The
transmissivity of aquifer A-1 was estimated using equation 9, where Qc was the
pickup in the 1,000-foot reach (0.2 cfs or 129,600 gpd), ASc was an insignificant
value, L was 1,000 ft, Ii was the hydraulic gradient from the lake (0.0073), and
la was the hydraulic gradient from the agricultural area (0.000154)
Qc ASc 129,600 gpd
L (Ii + Ia) 1,000 ft (.007454)

= 17,500 gpd/ft.

Thus results of the tests indicate that the transmissivity of aquifer A-1 is
about 17,500 gpd/ft and that permeabilities of confining beds C-l and C-2 are
low.
SEEPAGE

Seepage from the lake at site 3 can be estimated best by using the
transmissivity of the water-bearing strata that underly the dike and the average
hydraulic gradients therein. On the other hand seepage from the lake can be
related to the head across the dike if the head in the aquifer is directly related to
the head across the dike. Seepage through a 1,000-foot long section of aquifer
A-I on May 18, 1966 was 0.2 cfs when the stage of the lake was 13.75 ft and the
stage of the toe ditch was 7.44 ft. The transmissivity and drainage conditions
were considered to be uniform along the 1,000-foot section of dike which was
represented by the steady-state water levels at site 3. The seepage was expressed
in terms of the seepage factor (Se), which was determined by using equation 10,
where Q1 is 0.2 cfs, L is 0.189 mile, hi is 13.75 ft., and he is 7.44 ft.
Qr
se -
L(h1 hc)

0.2 cfs
0.189 mi (13.75 ft 7.44 ft)

= 0.168 cfs/mi/ft.

Thus the seepage factor at site 3 is about 0.2 cfs per mile per foot of head
between the water level in the lake and the water level in the toe ditch. The





REPORT OF INVESTIGATION NO. 58


seepage factor includes the head losses which might be attributed to the
filtercake in the Navigation Canal; however, seepage from the lake will decrease
as the filtercake, which was partly removed during construction activities in
1964, is redeposited.
Estimation of the increase in seepage that would result from raising the
average stage of the lake from 14 feet to 16.5 feet requires a knowledge of the
long-term relationships between the lake level and the water level in aquifer A-i
at the toe of the dike. Because those data are lacking, it must be assumed that
some of the water-level data collected at site 3 during 1964 are representative of
the long-term seepage conditions prior to changes in drainage and that some of
the water-level data collected during 1965-66 are representative of the
conditions which might be expected if a constant head drainage ditch, such as
the ditch at site 3, were excavated into aquifer A-1 along the landside toe of the
entire 8%-mile section of dike represented by site 3.
Prior to the excavation of the toe ditch at site 3 the average water level in
aquifer A-1 at the foot of the dike was probably at a stage of about 12.5 feet;
therefore, when the average lake stage was 14 feet, the average rate of seepage
was about 0.3 cfs per mile. If no changes in drainage occurred and the average
stage of the lake was raised to 16.5 feet, then the seepage would have increased
from 0.3 to about 0.8 cfs per mile.
During 1965-66, the water level in the toe ditch at site 3 was controlled by
pumping at a stage of about 9 feet; therefore, the average rate of seepage was
about 1.0 cfs per mile when the average lake stage is 14 feet. If the average stage
of the lake is raised to 16.5 feet then the seepage would increase from 1.0 to
about 1.5 cfs per mile.
Due to the excavation of the toe ditch, the seepage at site 3 is not
representative of the seepage along the assigned 8%-mile length of dike. The
seepage along the 8% miles of dike is considered to be related to the conditions
at site 3 prior to excavation of the ditch, therefore, seepage from the lake along
the 8 miles can be expected to increase from about 2.6 to 6.8 cfs as a result of
raising the average lake stage from 14 to 16.5 feet. However, if a toe ditch
similar to that at site 3 is excavated along the 8-miles of dike and the water level
therein is controlled at a stage of 9 feet, then seepage from the lake will increase
from 8.0 to 12.8 cfs if the average stage of the lake is raised from 14 to 16.5
feet.

SITE 4

DESCRIPTION

Site 4, as shown in figure 30, is in Palm Beach County on the southeastern
shore of Lake Okeechobee about, 3 miles northwest of Belle Glade. The site





BUREAU OF GEOLOGY


BELLE GLADE X'
EXPLANATION


PUMP STATION
PUMP
---- CITY BOUNDARY
0 I Z MILES


Figure 30. Map showing location of site 4 near Belle Glade.



consists of data-collection stations along a line about 1,400 feet long, as shown
in figure 31, which was constructed normal to the Hoover Dike. The stations
include 10 test wells, of which 6 were used to obtain data on ground-water
levels, and two observation points (OP's) which were used to obtain water-level
data in the lake and in the system of drainage canals in the nearby agricultural
area. North of the dike is the Navigation Canal which was excavated in the
thirties for borrow to construct the Hoover Dike. In 1963, borrow was taken
from the west side of the Navigation Canal to raise the dike to its present height,
as shown on the figure 31. South of the dike is a shallow ditch about 80 feet






REPORT OF INVESTIGATION NO. 58 71


S \ EXPLANATION
. I\ II -J o
ZU. 1 0 W ILL
0 9 '80 N e k a OBSMRVATION POINT
'DII I\ \ "\ -- ItIGHT-W-WAT LUI

e \ D-d Lmas Orra ran
-200 0 200 400 600
RANGE,FEET
D PLAN D
40
HOOVER DIKE
0 I FILL fine quartz sand, shell,
LAKE OKEECHOBEE and limestone fragments.
LAKE SOIL organic, black, sandy.
SSILT organic, black, sandy.
2 4NAVIGATON CANAL LI=MSTONE gray, hard to soft,
shelly; grades into marl.
o M NARL white to gray, sticky.
o LDIBSTONE brown, hard, dense.
SIBLL white, hard to soft;
chiefly Helisoma sp.,
SEA = Fontigens ap., Chione sp.,
LEVEL L and Astarte sp.; and some
sand.
... r^ ^ LDSTONI gray, hard, porous,
d shelly.
O SAND quartz, fine to coarse,
with som shell.
*a LDUSTOaH gray, hard, sandy,
-200 0 200 400 porou
RANGE,FEET
PROFILE
(STATION 980)




Figure 31. Plan and profile along line D-D' at site 4.

wide, which parallels the toe of the dike. East of the ditch are fields which are
drained by a system of north-south lateral ditches that are about 6 feet deep.
The lateral ditches are spaced about 0.1 mile apart and they are connected to
larger east-west canals. Water in the east-west canals can be pumped into a main
north-south canal at State Road 715. Water levels in the agricultural area are
regulated by the South Florida Conservancy Drainage District.

Natural land surface ranges from 13 to 14 feet above msl and is underlain
by about 8 feet of organic soil (fig. 31). Beneath the soil are beds of shell, marl,
limestone, and sand, which grade laterally and vertically into each other.
Generally beds of limestone and shell comprise aquifers, and beds of organic soil,
marl, clay and fine sand comprise confining beds. Seepage is probably greatest
through permeable beds of limestone and shell that range between 2 and 6 feet
above msl in the Fort Thompson Formation and through a permeable bed of
limestone that ranges between 2 and 12 feet below msl in the Caloosahatchee
Marl.






72 BUREAU OR GEOLOGY


AQUIFERS AND CONFINING BEDS


Aquifers, confining beds, and the depths of observation wells along line
D-D' are shown on profile A in figure 32. The aquifers and confining beds are
numbered consecutively with increasing depth from land surface and the
numbers are peculiar only to site 4.


w> -
0 0 0 -o bUJ b C
i- r) C -





0wJ zz
--y vi I-- o _<
0
SLL <
-ZL


I L i





o I C- 0' _. J






L um lz o
0 (-- -l
W W ..<. ( -








S" ,, 0- I W_1
0 0 <





I *- -o o o_ u w u_


: ,l -o -
o ___ j y


Figure 32. Selected hydraulic profiles along line D-D' showing aquifers,
confining beds and depths of observation wells at site 4.





REPORT OF INVESTIGATION NO. 58


Confining bed C-1 ranges from 8 to 10 feet thick and is composed of
relatively impermeable, silty, organic soil. Bed C-1 retards the movement of
water between the surface and the underlying beds, however its confining ability
is locally ineffective where the bed is penetrated by canals and drainage ditches.
Aquifer A-1 ranges from 0 to 4 feet thick and is composed of porous, permeable,
gray limestone which grades laterally and vertically into clayey marl. The
permeability of bed A-1 is locally high in solution zones. Confining bed C-2
ranges from 5 to 6 feet thick and is composed of shelly marl and limestone. Bed
C-2 is relatively impermeable and confines water in the underlying aquifer.
Aquifer A-2 ranges from 7 to 8 feet thick and is chiefly composed of porous
limestone and shell. Confining bed C-3 is more than 6 feet thick and composed
of fine to coarse sand with some shell and local beds of sandy limestone. The
permeability of bed C-3 is assumed to be low because of the fine sand content.
Some seepage occurs through each bed but aquifer A-2 is the chief
conveyor of seepage from the lake. Seepage .is greatest through aquifer A-2
because it is highly permeable and it is exposed to direct infiltration from the
lake in the new borrow on the west side of the Navigation Canal. Seepage
through aquifer A-1 is retarded by the silt deposit, or filtercake, which lines the
eastern wall of the Navigation Canal. Seepage through aquifer A-2 is expected to
slowly decrease as the filtercake is redeposited on the walls of the new borrow.

WATER MOVEMENT AND FLUCTUATIONS

The principal direction of water movement at site 4 is eastward from the
lake into the agricultural area. Short-termed reversals occur when the level of the
lake is routinely lowered by the Corps of Engineers to create storage space
prior to the annual rainy season. Hydraulic profiles A and B in figure 32 were
constructed from water level data for June 4, 1965 and October 11, 1965,
respectively, to show the direction of seepage and the distribution of
equipotential lines and isochlors for low and high stages of the lake.
On June 4, 1965, a time of low water levels, the stage of the lake was
12.46 feet above msl and the stage of a ditch east of site 4 in the nearby drainage
system in the agricultural area (shown in fig. 30) was about 10.4 feet. Water
moved eastward from the lake through aquifers A-1 and A-2 toward the drainage
system. The water levels in aquifer A-1 had been lowered by the drainage
operations in the nearby fields however the water levels in aquifer A-2 had
apparently been unaffected. The close spacing of the equipotential lines in beds
C-1 and A-1 near the Navigation Canal indicates a relatively large loss in head
occurred across the filtercake that lines the navigation Canal. Water movement in
aquifer A-2 was chiefly eastward toward a distant point of discharge, probably
the deep canals near State Road 715. The nearly horizontal equipotential lines in
bed C-2 suggest that the bed confines the water in aquifer A-2 and that some
water seeps upward from bed A-2 into bed A-1.





BUREAU OF GEOLOGY


The 50 mg/1 chloride content in aquifer A-1 suggest that part of the water
in the aquifer A-i was diluted by local rainfall because the chloride content in
the lake and in aquifer A-2 was between 70 and 80 mg/1. The nearly uniform
chloride content in the lake and in aquifer A-2 indicates that the seepage from
the lake occurs chiefly through aquifer A-2. About 200 mg/1 chloride content
was found in the canal water at State Road 715, about % mile east of site 3,
suggesting that most of the surface water in the agricultural area is derived from
a source other than seepage from the lake.
On October 11, 1965, a time of high water levels, the stage of the lake was
14.45 feet and the stage of a ditch in the agricultural area near State Road 715
(shown in fig. 30) was about 8.8 feet. Water moved eastward from the lake
through aquifers A-i and A-2 toward the agricultural area. Water levels in aquifer
A-I had been lowered by the drainage operations in the nearby fields. However,
the water levels in aquifer A-2 were relatively unaffected by the nearby surface
drainage, a condition which indicates that most of the seepage through aquifer
A-2 moved eastward beneath the nearby ditches and canals toward a more
distant discharge point in the agricultural area. The chloride content of the canal
water near State Road 715 was about 400 gm/l, which suggest that most of the
surface drainage is related to a source other than the lake because the.lake water
contained 120 mg/1 chloride. Chloride content in the lake at site 4 is usually
highest during wet periods when excess water is pumped from the agricultural
area into the lake.
A graphical comparison of the fluctuations in the stage of the lake and the
water level in well 1, which is located east of the dike and taps aquifer A-1, with
local rainfall shows that the water level in well 1 is chiefly influenced by local
rainfall, shown on figure 33. Water level peaks were caused by rain, and water
level troughs were caused by local drainage operations. The relationship between
drainage operations and the water-level fluctuations in well 1 indicates that the
nearby drainage ditches tap aquifer A-1. Water levels in the nearby fields are
probably controlled at a stage of 11 feet.
Water levels, chloride content and water temperature in wells that tap
aquifers A-1 and A-2, respectively, are compared with data for the lake in figures
34 and 35. The lines are coded with dots and the line with the least number of
dots represents the well nearest to the lake.
The water levels in the wells tapping aquifer A-i fluctuated between 1 and
4 feet below the stage of the lake (fig. 34). The relatively small spread between
the water levels in the wells shows that the hydraulic gradient .in the aquifer
beneath the dike was relatively low. Because of the low hydraulic gradient, the
rate of seepage from the lake in aquifer A-i is probably slow. The chloride
content in well 2, located nearest the lake, is generally less than that of the lake.







REPORT OF INVESTIGATION NO. 58 75


S161 1 1 11 1
1 I19164
>5 DAILY MEAN LAKE STAGE
DAILY HIGH GROUND WATER STAGE
<-J~ ~iLAND SURFACE DATUM AT WELL I
S14 13.33 FEET MEAN SEA LEVEL
- o 1 1 111,1 1121
W13







4 -2.20 2.14 2.61 I 2.70 1.34 5.23 5.73 7.63 2.12 9.62 0.82 2.91

$ ^ 3 BELLE GLADE EXP



JFMAMJJASO N D
w 1965

4
W11














102


















5 0.26 3.44 2.36 1.11 1.52 11.25 7.073 7.16 4.53 9.16 0.32 1.38
-jcn
0 4















J F M A M J J A S O N D



















Figure 33. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 1 at site 4; and daily and monthly
rainfall at Bele Glade; 19665.
15

jW
W ( 14
W -
W 13







4 _9.26 3.44 2.36 I 6 0.32 1.3I




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




Figure 33. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 1 at site 4; and daily and monthly
rainfall at Belle Glade; 1964-65.






BUREAU OF GEOLOGY


J F M AM J J A S ON DIJ F M A M J J A S 0 I
1964 EXPLANATION 1965

LAKE ---WELL I
---WELL 2 ----WELL 3

Figure 34. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-I at site 4 with data for
the lake, 1964-65.


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REPORT OF INVESTIGATION NO. 58


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1964 EXPLANATION 1965

LAKE ----WELL 5
-- WELL 4 -----WELL 6

Figure 35. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-2 at site 4 with data for
the lake, 1964-65.


I I I I II I I I I I I


I I





BUREAU OF GEOLOGY


The lower chloride content in wells 1 and 3, however, suggests that some low
chloride source, such as local rainfall on the east side of the dike, accounts for a
large part of the water in aquifer A-1 at this site. Fluctuations of water
temperature in aquifer A-i lag fluctuations of temperature in the lake, a
condition which suggests that the rate of seepage from the lake is relatively slow,
if the temperature changes in aquifer A-1 are due to seepage from the lake. Thus
the data suggest that the drainage ditches in the nearby fields tap aquifer A-l,
that the drawdown effects from pumping the ditches extends beneath the dike;
and that seepage from the lake is retarded by the filtercake in the Navigation
Canal.

The water levels in aquifer A-2 at site 4 are slightly lower than the water in
the lake (fig. 35). Generally, the water level in well 4, located nearest the lake,
fluctuated in concert with that of the lake, while the water levels in wells 5 and
6, located farthest from the lake, were only slightly affected by drainage
operations in the agricultural area. During 1964-65, the chloride content and
temperature in the wells tapping aquifer A-2 were nearly constant whereas the
chloride content and temperature of the lake fluctuate seasonally. The
temperature, chloride, and water-level data suggest that the seepage rate through
aquifer A-2 is slow, and that the aquifer probably conveys a relatively small
amount of seepage from the Navigation Canal in the lake to the drainage system
in the agricultural area. The fact that water levels in aquifer A-2 were relatively
unaffected by local drainage operations indicates that confining bed C-2 is
relatively impermeable.



QUANTITATIVE STUDIES


Aquifer tests were conducted at site 4 to determine the transmissivity
and/or the hydraulic conductivity of the water-bearing materials underlying the
dike. A pumping test was conducted in well 5 which taps aquifer A-2. Well 5 was
pumped for 95 minutes at a rate of 37 gpm while fluctuations of the water levels
in the aquifer were measured in observation wells 4 and 6. The results of the test
indicate that the transmissivity of aquifer A-2 is about 24,000 gpd/ft. Slug tests
were performed in wells 1 through 6 to determine the hydraulic conductivities
of the materials. The results of the tests were highly variable, indicating that Kf
(the hydraulic conductivity) of aquifer A-1 could range from 100 to 4,000
gpd/ft and the Kf of aquifer A-2 could range from 1,000 to 2,000 gpd/ft2. On
the basis of the lithology and the slug tests, it was concluded that the
transmissivity of aquifer A-1, (slightly more than a foot thick in places) is about
4,000 gpd/ft and the tranmissivity of aquifer A-2 (about 8 feet thick) is about
16,000 gpd/ft (table 5).





REPORT OF INVESTIGATION NO. 58 79


TABLE 5. RESULTS OF SLUG TESTS AT SITE 4.
Maximum
Thickness Kf T
Bed (feet) (gpd/ft2) (gpd/ft)
Dike Fill
A-1 4 100- 1,000 400- 4,000
A-2 8 1,000- 2,000 8,000- 16,000


However, on the basis of the combined results of the tests, it was estimated that
the transmissivity of aquifer A-1 is 4,000 gpd/ft and that the transmissivity of
aquifer A-2 is 24,000 gpd/ft; and these values were used to compute seepage
from the lake.


SEEPAGE

Seepage from the lake at site 4 can be estimated best by determining the
flow through 25 feet of saturated material underlying the dike. The flow
through the materials for a given period can be determined if the transmissivities
of the aquifers within the materials and the hydraulic gradients are known. A
comparison of the fluctuation of water levels in wells in the agricultural area
with that of the lake shows that hydraulic connection exists, and comparison of
water levels in wells and the lake at a given time establishes the gradient.
Therefore the seepage through aquifers A-1 and A-2 was computed for June 6,
1965, a time of low water levels, and for October 11, 1965, a time of high water
levels; and the seepages were related to the hydraulic gradient between the lake
and the water level in well 1 in order to determine the seepage factor (Se) in the
same manner as shown in the previous sections pertaining to seepage at sites 1, 2,
and 3. The results of the analysis are shown in table 6.



TABLE 6. RESULTS OF SEEPAGE ANALYSIS AT SITE 4.


QA-1 QA-2 Qtotal Se
Date (cfs/mi) (cfs/mi) (Cfs/mi) (cfs/mi/ft)

6-4-65 0.01 0.24 0.25 0.12
10-11-65 0.03 0.41 0.44 0.13


The seepage factor at site 4 is about 0.1 cfs per mile per foot of head between
the lake and well 1.





BUREAU OF GEOLOGY


The geologic cross section prepared by the Corps of Engineers (1961, plate
17) indicates that there is considerable variation in the material underlying the
10-mile section of dike represented by site 4. Even so, the seepage factor at site
4 is estimated to be within the order of magnitude which would be expected
for the type of material. The seepage factor includes the present retarding effect
of the filtercake in the Navigation Canal. The seepage factor at site 4 will
probably decrease in the future as the filtercake is slowly redeposited on the
exposed portions of the aquifers in the bottom of the Navigation Canal.
Long-term water-level data in the nearby agricultural area are needed to
determine the average seepage from the lake. These data are lacking. However
water-level data for well 1 during 1964-65 (see fig. 33) suggest that the
operations in the nearby drainage district control the water levels in the nearby
fields at about a stage of 11 feet. On this basis, the average rate of seepage from
the lake at site 4 would probably be about 0.3 cfs/mi when the average lake
stage is 14 feet, and about 0.55 cfs/mi when the average lake stage is 16.5 feet.
Therefore seepage from the lake along the 10-mile section of dike represented by
site 4 should increase from 3 to 5.5 cfs if the average lake stage is raised from 14
to 16.5 feet.
SITE 5

DESCRIPTION

Site 5 is in Palm Beach County on the eastern shore of Lake Okeechobee
about 1.2 miles north of Canal Point, as shown in figure 36. The site consists of
data-collection stations along a line about 1,600 feet long which was constructed
normal to the Hoover Dike. The stations include 9 test wells, of which 6 were
used to obtain data on ground-water levels, and two observation points which
were used to obtain water level data in the lake and in the landside toe ditch,
shown in figure 37. West of the dike is the lake and the Navigation Canal which
was excavated in 1964 for borrow to raise the Hoover Dike to its present height.
The filled channel on the west side of the Navigation Canal was excavated for
borrow to construct the dike in the early thirties and was backfilled with organic
material in 1964. East of the dike is a shallow toe ditch which conveys runoff
and seepage southward to the West Palm Beach Canal at Canal Point. East of the
ditch is the Florida East Coast Railroad and a 200-foot wide sand ridge on which
U. S. Highway 441 and most of the residences and businesses are located. About
0.6 mile east of U. S. Highway 441 is a drainage canal used for flood control by
the Pelican Lake Drainage District (not shown on fig. 37).
Natural land surface ranges from 15 feet above msl at the landside toe of
the dike to 19 feet at the top of the sand ridge. The area is underlain by 7 to 8
feet of organic soil, 3 to 4 feet of marl, 23 feet of shell and hard crystalline
limestone, and at least 15 feet of fine sand (fig. 37). Generally, beds of limestone
and shed are aquifers and beds of organic soil, marl, and fine sand are confining






REPORT OF INVESTIGATION NO. 58


EXPLANATION

PUMP
-- TOE DITCH

0 I 2 MILES
t !_


Figure 36. Map showing location of site 5 near Canal Point.








EXPLANATION
WILL
OBSERVATICWN OINT
RIGHT-OF-WAY LINK
ROAD
LIIN OF PIOFIL


P'LAT4


HOOVER DIKE LAKE OKEECHOoEE
30-
U.& HWY 441

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DIT@N TME ISLAND
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fragments; crushed granite
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O SAND quartz, fine.
SSOIL organic, black, sandy.
SILT organic, black; and sand.
iMAIL brown to white, shelly.
SELL white to gray, soft.
I LINSTOHI gray, very hard to
soft, shelly, porous.
* LIM182TO gray, soft, shelly;
with layers of sand.
S SP0 qvuarts, fine, shelly.


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RANGE, FEET
PROFILE


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REPORT OF INVESTIGATION NO 58


beds. The shelly limestone which underlies the dike between 12 and 20 feet
below msl in the Caloosahatchee Marl is the most permeable unit.

AQUIFERS AND CONFINING BEDS

The aquifers, confining beds, and depths of observation wells along line
E-E' at site 5 are shown on profile A in figure 38. The aquifers and confining
beds are numbered consecutively with increasing depth and the unit numbers are
peculiar only to site 5.
Confining bed C-1 has a maximum thickness of 12 feet. The upper 8 feet is
organic soil and the lower 4 feet is clayey shelly marl. The bed is about 9 feet
thick beneath the sand ridge and about 3 feet thick beneath the dike. Bed C-1 is
relatively impermeable and confines the water in the underlying aquifer. Aquifer
A-1 has a maximum thickness of 22 feet. The upper 2 feet is permeable shell and
soft permeable limestone which is underlain by a 12-foot bed of hard crystalline
limestone that locally contains stringers of sand. The lower 8 feet is soft, porous,
shelly limestone that locally contains stringers of sand.
Confining bed C-2 is at least 15 feet thick. It is chiefly composed of fine,
quartz sand and it is relatively impermeable.


WATER MOVEMENT AND FLUCTUATIONS

The principal direction of water movement at site 5 is eastward from the lake
toward the drainage canals in the agricultural area. Short term reversals occur
however when the water levels in Lake Okeechobee are routinely lowered by the
Corps of Engineers prior to the annual rainy season and water flows westward
toward Lake Okeechobee. Hydraulic profiles A and B in figure 38 were
constructed for June 4, 1965 and October 11, 1965 respectively, to show the
direction of seepage, and the distribution of equipotential lines and isochlors for
high and low stages of the lake.

On June 4, 1965, a time of low water levels, the stages of the lake and the
water level in the toe ditch were about 12.4 feet. Flow through confining bed
C-1 was chiefly westward from the sand ridge toward the toe ditch. However,
seepage into the ditch was insignificant due to the low permeability of the
confining bed. The widely spaced equipotential lines show that flow through
aquifer A-1 was eastward from the lake toward the drainage canals in the
agricultural area, and that the hydraulic gradient was low. The nearly horizontal
equipotential lines beneath the sand ridge at U. S. Highway 441 indicate the loss
in head across confining bed C-1. Flow through aquifer A-1 was eastward toward
the drainage canals in the Pelican Lake Drainage District. Seepage was induced
by pumping in the agricultural area at the time of the measurement.








OCTOBER 11,1965


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CONFINING BED DISCUSSED
IN TEXT BY NUMBER
O AQUIFER DISCUSSED IN
TEXT BY NUMBER
] FILL
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EEAST


1000 -400
RANGE, FEET
EXPLANATION


WEST40
r40


0 400 800 1000


_= DIRECTION OF FLOW
-1400- EQUIPOTENTIAL LINE VALUE IS
FEET ABOVE MEAN SEA LEVEL
ISOCHLOR VALUE IS
80MILLIGRAMS PER LITER
6* WELL NUMBER AND
UNCASED PORTION


JUNE 4,1965






REPORT OF INVESTIGATION NO. 58


On October 11, 1965, at time of high water levels, the direction of flow
through confining bed C-1 was eastward from the lake and westward from the
ground-water mound beneath the sand ridge toward the tow ditch. However, no
significant flow was observed in the toe ditch, which confirmed that bed C-1 is
relatively impermeable.
Flow through aquifer A-1 was eastward from the lake toward the drainage
system in the agricultural area. Comparison of the spacing of the equipotential
lines in the profiles indicates that the rate of flow on October 11 was more than
twice the rate during June 4; and the eastward shift ofisochlors on October 11
also indicates that flow from the lake through aquifer A-1 had increased.
The daily stages of the lake and the water level in well 2, located at the toe
of the dike and tapping aquifer A-i, are compared on figure 39. The water level
in well 2 fluctuates primarily in response to changes in the level of the lake.
Short-term fluctuations in the well were caused by seiche and wind tides in the
lake and by drainage operations in the agricultural area east of the dike.
Drawdown in the well by the drainage was greatest after heavy rains in mid
October 1964, but daily drawdowns of a few hundredths of a foot were
common. The data indicate that there is a linear relationship between the stage
of the wells and the stage of the lake and that locally a good hydraulic
connection occurs between the lake and aquifer A-1.
Water levels, chloride content, and water temperatures in confining bed C-1
and aquifer A-1 are compared with data for the lake in figures 40 and 41,
respectively. The data on the graphs are coded so that the line with the least dots
represents the well nearest the lake.
Water levels in well 3 located west of the dike in bed C-1 compare
well with the stage of the lake while the water levels in wells 4 and 5 located east
of the dike do not (fig. 40). The water level in well 4 landsidee toe of dike) is
about comparable to the water level in the toe ditch which drains southward
into Palm Beach Canal. The water level in well 5 indicates that water levels
beneath the sand ridge are oft n higher than the lake level.
Prior to'the excavation of the toe ditch in August 1964, the area between
the dike and the sand ridge was periodically inundated following periods of
heavy rainfall. Many local residents believed that the flooding was caused by
seepage from the lake. However, hydrologic data, and on site investigation of the
flooded area have led this investigator to conclude that flooding was due chiefly
to inadequate surface drainage and to seepage.westward from the sand ridge and
not due to seepage from the lake. For example, on July 8, 1964 the water level
in the area between the toe of the dike and the railroad was 15.45 feet above msl
(more than a foot above land surface) while the stage of the lake was only 13.2
feet. Obviously, the direction of seepage must have been toward the lake and not
from the lake. Therefore the observed flooding at that time was caused by
runoff that was trapped in the small basin between the railroad and the dike.





BUREAU OF GEOLOGY


\ I I I 1\ 19 164 1 -1 \1 1
-- DAILY MEAN LAKE STAGE
ws DAILY HIGH GROUND WATER STAGE AT WELL 2
-7 LAND SURFACE DATUM AT WELL 2
4 14.42 FEET MEAN SEA LEVEL



1S926

5 I
S4 3.32 2. 0.93 3.67 2.05 13.52 9.02 8.59 5.65 663 0.45 443
3 CANAL POINT
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J F M A M J J A S O N D

Figure 39. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 2 at site 5; and daily and monthly
rainfall at Canal Point; 1964-65.


After the toe ditch was excavated the water level in well 4 declined and since
then no flooding has been observed.
Water levels in observation wells 1, 2 and 6 that tap aquifer A-1 fluctuate
in concert with the level of the lake, as shown by the hydrographs on figure 41.
The water levels in the aquifer slope eastward away from the lake, thus the flow
is eastward from the lake. Water levels in the wells were slightly affected by
drainage operations in the agricultural area. Well 6, which is closest to the
agricultural area, was affected most by pumping from the drainage canal located
0.7 mile east of the dike.
The chloride content in the lake at site 5 appears to be highest during the
wet periods when water containing high chloride is pumped from the agricultural






REPORT OF INVESTIGATION NO. 58


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- LAKE
--- WELL 3


---- WELL 4
--- WELL 5


Figure 40. Graphs comparing water levels, chloride content, and water
temperature in wells that tap confining bed C-1 at site 5 with the
data for the lake, 1964-65.


200 r i II Iii i










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SA J J A S 0d J F M A M Ji A S 0
1964 EXPLANATION 1







BUREAU OF GEOLOGY


1964 EXPLANATION 1965

- LAKE ---- WELL 2
--- WELL I --.--WELL 6


Figme 41. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-i at site 5 with data for
the lake, 1964-65.


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REPORT OF INVESTIGATION NO. 58 89


area into the lake. The chloride and temperature data appear to show no direct
relation between water in the lake and wells. Perhaps the reason for the
nonconformity of the data can be partly attributed to the lack of good
circulation at the lake sampling point, which was located in the lagoon between
the dike and the tree islands, and to recharge from the toe ditch and the sand
ridge when water levels there were higher than water levels in aquifer A-1.

QUANTITATIVE STUDIES

Aquifer tests were conducted at site 5 to determine the transmissivity (T)
and/or hydraulic conductivity of the water-bearing materials underlying the
dike. Attempts were made to perform pumping tests at the site but the yields of
the wells were insufficient to provide meaningful data. Slug tests were conducted
in wells 1 through 4 with equally poor results because the wells were either
partly filled with sand or lacked sufficient open hole in the limestone to allow
the water to freely enter the well. But a few data indicate that hydraulic
conductivity of the lower 4 feet of bed C-1 is about 4.6 gpd/ft2, and that the
hydraulic conductivity of the upper 14 feet of aquifer A-1 is about 70 gpd/ft2
(table 7).

TABLE 7. RESULTS OF SLUG TESTS AT SITE 5


Thickness K T
Bed (feet) (gpd/ft2) (gpd/ft)

C-1 4 4.6 18.4
A-12 14 66.0 924.0

1 Marl in lower part of C-1.
2 Hard limestone and shell in upper part of A-1.

Water-level fluctuations in well 2, which were induced by wind-driven tides
and seiche of the lake, were analyzed by a method suggested by Ferris (1962 p.
133); and the analysis indicated that the transmissivity of the upper 14 feet of
aquifer A-1 is about 1,200 gpd/ft.
Geologic data from wells 7-9 indicate that the shell which comprises the
lower 8 feet of aquifer A-1 at site 5 is equivalent to the permeable shell in
aquifer A-2 at site 1. The transmissivity of the total water-bearing section at site
1 is about 72,000 gpd/ft, however, the transmissivity of the 18.5 feet of shell
that comprises aquifer A-2 probably represents 63 percent of the total
transmissivity (72,000 gpd/ft), or about 45,400 gpd/ft., based on the ratio of the
T value for aquifer A-2 to the total T in table 2. Therefore the transmissivity of





90 BUREAU OF GEOLOGY


the lower 8 feet of aquifer A-1 at site 5 would be 43 percent (8 ft/18.5 ft) of the
T value for aquifer A-2 at site 1, or 19,500 gpd/ft. Thus the total transmissivity
of the aquifer A-i at site 5 would be the sum of the T values for the upper
14-foot section (1,200 gpd/ft) and the lower 8-foot section (19,500 gpd/ft), or
20,700 gpd/ft.

SEEPAGE

Seepage from the lake at site 5 can be estimated best by determining the
steady-state flow for a given period through 33 feet of saturated material
underlying the dike. As explained in the proceeding sections dealing with seepage
at sites 1 through 3, the flow through the materials for a given period can be
determined from the transmissivities and the prevailing hydraulic gradients.
Seepage was computed from water-level measurements made on January
14, June 4, and October 11, 1965. Seepage through confining bed C-1 (Qc-1)
was computed using the prevailing hydraulic gradient between wells 3 and 4 and
a transmissivity of 50 gpd/ft. Seepage through aquifer A-1 (QA-1) was computed
using the prevailing hydraulic gradient between wells 1 and 2 and a
transmissivity of 20,700 gpd/ft. The seepage factor, Se, was determined by
relating the total seepage through beds A-1 and C-1 to the head between the lake
and well 2 which taps aquifer A-i and is located at the landward toe of the dike.
The results of the analysis are shown in table 8.


TABLE 8. RESULTS OF SEEPAGE ANALYSES AT SITE 5.
H QCI QA-1 Qtotal Se
Date (ft) (cfs/mi) (cfs/mi) (cfs/mi) (cfs/mi/ft)

1-14-65 0.66 0.002 0.246 0.248 0.38
6-4-65 .23 .0002 .0845 .0847 .37
10-11-65 .64 .003 .193 .196 .31



The average seepage factor at site 5 is about 0.4 cfs per mile per foot of
head between the lake level and the water level in well 2. The seepage factor
includes the present effects of the filtercake in the Navigation Canal, however,
seepage will probably decrease in the future as the filtercake is slowly
redeposited on the exposed portion of the aquifers in the bottom of the canal.
Long term water-level data in the agricultural area are needed to determine
the average seepage from the lake. However, these data are lacking, therefore the
relationship between the lake and well 2 was used to estimate the steady-state
hydraulic gradient between the lake and the discharge point in the agricultural






REPORT OF INVESTIGATION NO. 58 91


area. Seepage can be estimated for selected stages of the lake by multiplying the
head between the lake and the water level in well 2 by the seepage factor (0.4
cfs/mi/ft).

The relationship between the water levels of the lake and well 2 indicate
that when the stage of the lake is 14 feet, the water level in well 2 is about 13.64
feet. Therefore the head across the dike in aquifer A-1 would be about 0.36 foot
and the corresponding rate of seepage at site 5 would be 0.1 cfs/mile. If the
average stage of the lake is raised to 16.5 feet, then the average stage of the
water-level in well 2 would be about 15.6 feet and the average rate of seepage
would be 0.4 cfs/mile.
Thus seepage beneath the 14-mile segment of dike represented by site 5
should increase from 1.4 cfs to 5.6 cfs if the average lake stage is raised from 14
feet to 16.5 feet.



SEEPAGE ALONG SOUTHERN SHORE
OF LAKE OKEECHOBEE

Studies of seepage at five sites along the southern shore of Lake
Okeechobee indicate that seepage factors ranged from 0.9 cfs/mi/ft at site 1 near
Moore Haven to 0.1 cfs/mi/ft at site 4 near Belle Glade (table 9).

TABLE 9. SUMMARY OF SEEPAGE BENEATH HOOVER DIKE
ALONG THE SOUTHERN SHORE OF LAKE OKEECHOBEE

Se seepage factor, cubic feet per second per mile per foot of head across the dike.

L length of dike assumed represented by each site, miles.

S14 seepage rate for average stage 14 feet, cfs per mile.

S16.5 seepage rate for average stage 16.5 feet, cfs per mile.

T14 total seepage along L for stage 14 feet, cfs.

T16.5 total seepage along L for stage 16.5 feet, cfs.

SITE Se L. S14 S16.5 T14 16

1 0.9 9.0 1.6 3.4 14.4 30.6
2 .2 8.5 .1 .15 .8 1.3
3 .2 8.5 .3 .8 2.6 6.8
4 .1 10.0 .3 .55 3.0 5.5
5 .4 14.0 .1 0.4 1.4 5.6

T'TA T 50.0 22.2 49.8


rvr~ruu


. -





BUREAU OF GEOLOGY


When the average stage of the lake is 14 feet, seepage beneath the Hoover Dike
ranges from 1.6 cfs/mi at site 1 near Moore Haven to 0.1 cfs/mi at site 2 near
Clewiston and at site 5 near Canal Point. Seepage is greatest at site 1 because
deep borrows, located adjacent to both sides of the dike, penetrated permeable
beds of shell, and hydraulic gradients there are steep.
Seepage is expected to increase as a result of raising the average lake stage
from 14 to 16.5 feet. Seepage along the 50-mile shoreline between Moore Haven
and Port Mayaca should increase from 22 to 50 cfs as a result of raising the
average lake stage 2.5 feet. The 22 cfs seepage loss at stage 14 feet is equivalent
to 0.43 in/yr loss from lake storage and the 50 cfs seepage loss at stage 16.5 feet
is equivalent to 1.00 in/yr loss from the lake. The seepage rates determined
during this study compare favorably with rates determined previously by the
Corps of Engineers (1963). The seepage rates presented herein are only valid for
the conditions which prevailed at each site. Changes in agricultural drainage
could greatly increase the seepage if, for example, drainage ditches were
deepened so that they penetrated confining beds, drainage ditches were dug
closer to the dike, and water levels in nearby fields were lowered. However,
seepage from the lake into the agricultural area can be controlled by the
C&SFFCD if a system of toe ditches and canals were designed to intercept
seepage from the lake through the chief aquifers underlying the dike. This
seepage could then be returned to the lake by pumping. Ai authorized pumping
station (S-4) to be constructed near site 1 will intercept seepage from the lake
between Moore Haven and Clewiston by controlling the stages of the LD1 canal.


SUMMARY

Studies were made of seepage from Lake Okeechobee beneath the Hoover
Dike at five selected sites along the southern shore of Lake Okeechobee. The
objectives of the studies were to describe the manner in which seepage was
occurring, to determine the seepage rate at each site, and to estimate the increase
in average seepage that would result if the average stage of the lake were raised
from 14 to 16.5 feet above msl.
Studies at site 1 near Moore Haven indicate that seepage from the lake
occurs chiefly through two contiguous aquifers that underlie the dike between
10 feet above msl and 20 feet below msl. The aquifers are composed of
limestone and shell and function hydraulically as a unit. The total transmissivity
of the aquifers is about 72,000 gpd/ft and the seepage factor is about 0.9 cfs per
mile per foot of head between the lake level and the water level and the water
level in the nearby L-D1 Canal. Seepage from the lake into the agricultural area
depends upon the drainage operations in the agricultural area. During dry
periods the stage of the L-D1 Canal is regulated at, or slightly above, the desired
stage of the water table in the adjacent fields and the L-D1 canal intercepts most






REPORT OF INVESTIGATION NO. 58


of the seepage from the lake and conveys the water to the agricultural area.
During wet periods the L-D1 Canal is ponded by controls, and water from the
lake seeps southward through the L-D1 Canal into the nearby fields. If the
average stage of the lake is raised from 14 to 16.5 feet then the average rate of
seepage at site 1 would increase from 1.6 to 3.4 cfs/mi and the average seepage
beneath the 8-mile length of dike represented by site 1 would increase from
14.4 to 30.6 cfs.

Studies at site 2 near Clewiston indicate that seepage from the lake occurs
generally through the upper 28 feet of strata. However, most seepage occurs
through an 8-foot thick limestone aquifer which has a transmissivity of 3,000
gpd/ft. Beneath the limestone is a bed of fine sand that retards the movement of
water from the lake into the agricultural area and into the underlying aquifers.
The seepage factor is about 0.2 cfs/mi per foot of head between the lake level
and the water level in the L-D2 Canal. If the average stage of the lake is raised
from 14 to 16.5 feet then the average rate of seepage at site 2 would increase
from 0.1 to 0.15 cfs/mi and the average seepage beneath the 8%-mile length of
dike represented by site 2 would increase from 0.8 to 1.3 cfs.
Studies at site 3 near Lake Harbor indicate that most of the seepage from
the lake occurs through a 17-foot thick aquifer composed of shell and porous
limestone. The transmissivity of the aquifer is about 17,500 gpd/ft. The seepage
factor is about 0.2 cfs/mile per foot of head between the lake level and the water
level in the toe ditch. If the average stage of the lake is raised from 14 to 16.5
feet then the average rate of seepage would increase from 0.3 to 0.8 cfs/mi and
the average seepage beneath the 8-mile length of dike represented by site 3
would increase from 2.6 to 6.8 cfs.
Studies at site 4 near Belle Glade indicate that seepage from the lake
occurs through two aquifers. The uppermost aquifer is 4 feet thick and is
composed of porous limestone. The transmissivity of the aquifer is about 4,000
gpd/ft. The lowermost aquifer is 10 feet thick and is composed of porous
limestone and shell. The transmissivity of this aquifer is about 24,000 gpd/ft.
The seepage factor is about 0.1 cfs/mi per foot of head between the lake level
and the water level in well 1, which taps the shallow aquifer and is located at the
landside toe of the dike. If the average stage of the lake is raised from 14 to 16.5
feet then the average rate of seepage at site 4 would increase from 0.3 to 0.55
cfs/mile and the average seepage beneath the 10-mile length of dike represented
by site 4 would increase from 3 to 5.5 cfs.
Studies made at site 5 near Canal Point indicate that most of the seepage
occurs through an aquifer 22 feet thick composed of shell and hard porous
limestone. The transmissivity of the aquifer at site 5 is estimated to be 20,700
gpd/ft on the basis of the transmissivity of similar material at site 1. The seepage
factor is estimated to be 0.4 cfs/mi per foot of head between the lake level
and the water level in well 2, which taps the aquifer and is located at the





94 BUREAU OF GEOLOGY


landside toe of the dike. If the average stage of the lake is raised from 14 to 16.5
feet then the average rate of seepage would increase from 0.1 to 0.4 cfs/mi; and
the average seepage beneath the 14-mile length of dike represented by site 5
should increase from 1.4 to 5.6 cfs.
If the average stage of the lake is raised from 14 to 16.5 feet, then the
seepage beneath the total 50-mile length of dike represented by the five sites
would increase from 22 to 50 cfs. Because of the large distances between sites,
variations in values can be expected in the intervening areas. Therefore the
results of these studies are only an indication of the seepage rates that might be
expected around the southern shore of Lake Okeechobee. The studies indicate a
need for additional data near South Bay and along the newly constructed dikes
on the northern shore of Lake Okeechobee, and for a monitoring program which
will be useful in determining the effects that deposition of filtercake in lakeside
borrows and changes in drainage works will have on future seepage rates.






REPORT OF INVESTIGATION NO. 58


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1967 (See Cooper, H. H.)
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1944 (See Parker, G. G.)
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1929 (and Mossom, Stuart) Geology of Florida: Florida Geol. Survey
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Cooke, C. W.
1945 Geology of Florida: Florida Geol. Survey Bull. 29.
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1967 (and Bredehoeft, J. D., and Papadopulos, I. S.) Response of a
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Dall, W. H.
1887 Notes on the geology of Florida: Am. Jour. Sci., 3rd Ser., v. 34.
Dall, W. H.
1893 Geological results from the study of the Tertiary fauna of Florida:
Wagner Free Inst. Sci. Trans., v. 3, pt. 6.
Davis, J. H.
1943 The natural features of southern Florida: Florida Geol. Survey
Bull. 25.
Dubar, J. R.
1958 Stratigraphy and paleontology of the late Neogene strata of the
Caloosahatchee River area of southern Florida: Florida Geol.
Survey Bull. 40.
Ferguson
1955 (See Parker, G. G.)
Ferris, J. G.
1962 (et al) Theory of aquifer tests: U. S. Geol. Survey Water Supply
Paper 1536-E.
Greene, F. A.
1966 (and Pruit, M. M.) Revised plan of reclamation, Diston Island
Drainage District: Gee & Jenson Consulting Engineers Inc., West
Palm Beach, Florida.
Heilprin, Angelo
1887 Explorations on the west coast of Florida and in the Okeechobee
wilderness: Wagner Free Inst. of Sci. Trans. v. 1.
Herr, Ben
1943 Caloosahatchee River and Lake Okeechobee drainage areas,
Florida: Soil Sci. Soc. Florida Proc., v. 5-A.


95






BUREAU OF GEOLOGY


Hull, J. E.
1969


(See Meyer, F. W.)


Johnson, Lamar
1951 (See Stephens, J. C.)
Jones, L. A.
1948 Soils, geology and water control in the Everglades region: Univ.
Florida Agr. Expt. Sta. Bull. 442.
Kenner, W. E.
1961 Stage characteristics of Florida lakes: Florida Geol. Survey Inf.
Circ. 31.
Klein, Howard
1954 (See Schroeder, M. C.)
Klein, Howard
1964 (and Schroeder, M. C. and Lichtler, W. F.) Geology and
groundwater resources of Glades and Hendry counties, Florida:
Florida Geol. Survey Rept. of Inv. 37.
Lichtler, W. F.
1960 Geology and groundwater resources of Martin County, Florida:
Florida Geol. Survey Rept. of Inv. 23.

Lichtler, W. F.
1964 (See Klein, Howard)
Love, S. K.
1954 (See Schroeder, M. C.)

Love, S. K.
1955 (See Parker, G. G.)
Mansfield, W. C.
1931a Pliocene fossils from limestone in southern Florida: U. S. Geol.
Survey Prof. Paper 170-D.

Mansfield, W. C.
1931b Some Tertiary mollusks from southern Florida: U. S. Nat. Mus.
Proc., v. 79, art. 21.
Mansfield, W. C.
1939 Notes on upper Tertiary and Pleistocene mollusks of peninsular
Florida: Florida Geol. Survey Bull. 18.
Matson, G. C.
1913 (and Sanford, Samuel) Geology and groundwaters of Florida: U.
S. Geol. Survey Water-Supply Paper 319.
Meyer, F. W.
1969 (and Hull, J. E.) Seepage tests in L-D1 Borrow Canal at Lake
Okeechobee, Florida: Florida Geol. Survey Inf. Circ. 59.
Milliken, D. L.
1954 (See Schroeder, M. C.)


Mossom, Stuart
1929 (i


fee Cooke, C. W.)






REPORTOF INVESTIGATION NO. 58


Olsson, A. A.
1964


Some Neogene Mollusca from Florida and the Carolinas: Bull. of
Am. Paleo. v. 47.


Papadopulos, I. S.
1967 (See Cooper, H. H.)
Parker, G. G.
1942 Notes on the geology and ground water of the Everglades in
southern Florida: Soil Sci. Soc. Florida Proc., v. 4-A.
Parker, G. G.
1944 Late Cenozoic geology of southern Florida, with a discussion of
the ground water: Florida Geol. Survey Bull. 27.
Parker, G. G.
1951 Geologic and hydrologic factors in the perennial yield of the
Biscayne aquifer, Miami area, Florida: Am. Water Works Assoc.
Jour.
Parker, G. G.
1955 (and Ferguson, G. E. and Love, S. K. and others) Water resources
in southeastern Florida: U. S. Geol. Survey Water-Supply Paper
1255.
Perkins, R. D.
1968 Late Cenozoic stratigraphy of southern Florida A reappraisal,
with additional notes on Sunoco-Felda and Sunniland oil fields:
Miami Geol. Soc. 2nd Ann. Field Trip Guide Book.
Pruit, M. M.
1966 (See Greene, F. A.)
Puri, Harbans
1964 (and Vernon, R. O.) Summary of the geology of Florida and a
guidebook to classic exposures: Florida Geol. Survey Spec. Pub. 5.
Roland, L. Orlando
1969 An application of geology to agriculture south of Lake
Oheechobee: Southeastern Section Geol. Soc. America, 18th,
Columbia, South Carolina 1969, Abstracts with programs for
1969.
Sanford, Samuel
1913 (See Matson, G. C.)
Schroeder, M. C.
1954 (and Klein, Howard) Geology of the western Everglades area,
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1964 (See Klein, Howard)
Schroeder, M. C.
1954 (and Milliken, D. L. and Love, S. K.) Water resources of Palm
Beach County, Florida: Florida Geol. Survey Rept. of Inv. 13.
Stephens, J. C.
1951 (and Johnson, Lamar) Subsidence of organic soils in the Upper
Everglades Region of Florida: U. S. Dept. Agriculture, Soil
Conserv. Service.





BUREAU OF GEOLOGY


Stringfield, V. T.
1933 Ground water in the Lake Okeechobee area: Florida Geol. Survey
Rept. of Inv. 2.


U. S. Corps
of Engineers
1953


U. S. Corps
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1961


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1962


U. S. Corps
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1963


Design Memorandum, Permeability investigations of well-pumping
tests: U. S. Corps of Engineers report on Central and Southern
Florida Project, Part 1, Supp. 7.


Detail Design Memorandum, Herbert Hoover Dike, Levees D-1 D-2
(part), and D-3 (Part): U. S. Corps of Engineers report on Central
and Southern Florida Project, Part 4, Supp. 14.


Detail Design Memorandum, Herbert Hoover Dike, Levees D2
(part), D9, and D4: U. S. Corps of Engineers report on Central
and Southern Florida Project, Part 4, Supp. 18.


General Design Memorandum, Nine-Mile Canal area: U. S. Corps
of Engineers report on Central and Southern Florida Project, Part
1, Supp. 39.


U. S. Geological Survey
1965 Water resources data for Florida: Water Resources Division, data
report.
Vernon, R. O.
1964 (See Puri, Harbans)
Wallis, W. T.
1942 The history of Everglades drainage and its present status: Soil Sci.
Soc. Florida Proc. v. 4-A.




Seepage beneath Hoover Dike, southern shore of Lake Okeechobee, Florida ( FGS: Report of investigations 58 )
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 Material Information
Title: Seepage beneath Hoover Dike, southern shore of Lake Okeechobee, Florida ( FGS: Report of investigations 58 )
Series Title: ( FGS: Report of investigations 58 )
Physical Description: iv, 98 p. : illus., maps. ; 23 cm.
Language: English
Creator: Meyer, Frederick W
Geological Survey (U.S.)
Publisher: Bureau of Geology
Place of Publication: Tallahassee
Publication Date: 1971
 Subjects
Subjects / Keywords: Water-supply -- Florida -- Okeechobee, Lake   ( lcsh )
Okeechobee, Lake (Fla.)   ( lcsh )
Seepage   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Frederick W. Meyer.
Bibliography: Bibliography: p. 95-98.
General Note: "Prepared by the United States Geological Survey in cooperation with the Bureau of Geology and the Central and Southern Florida Flood Control District, U.S. Army Corps of Engineers."
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Source Institution: University of Florida
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The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: aleph - 000835536
notis - AED1207
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Table of Contents
    Title Page
        Page i
        Page ii
    Transmittal letter
        Page iii
        Page iv
    Contents
        Page v
        Page vi
        Page vii
        Page viii
        Page ix
        Page x
    Abstract and introduction
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
    Geographic setting
        Page 9
        Page 10
        Page 11
        Page 12
        Page 8
    Geologic setting
        Page 13
        Page 14
        Page 15
        Page 12
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
    Geohydrology
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
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        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
    Seepage along southern shore of Lake Okeechobee
        Page 92
        Page 91
    Summary
        Page 92
        Page 93
        Page 94
    References
        Page 95
        Page 96
        Page 97
        Page 98
    Copyright
        Copyright
Full Text



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




DIVISION OF INTERIOR RESOURCES
J. V. Sollohub, Director




BUREAU OF GEOLOGY
Robert 0. Vernon, Chief




Report of Investigations No. 58




SEEPAGE BENEATH HOOVER DIKE
SOUTHERN SHORE OF LAKE OKEECHOBEE, FLORIDA




By
Frederick W. Meyer


Prepared by the
UNITED STATES GEOLOGICAL


SURVEY


in cooperation with the
FLORIDA DEPARTMENT OF NATURAL RESOURCES
DIVISION OF INTERIOR RESOURCES
BUREAU OF GEOLOGY
and the
CENTRAL AND SOUTHERN FLORIDA FLOOD CONTROL DISTRICT
U. S. ARMY CORPS OF ENGINEERS


TALLAHASSEE, FLORIDA
1971









DEPARTMENT
OF
NATURAL RESOURCES




REUBIN O'D. ASKEW
Governor


RICHARD (DICK) STONE
Secretary of State




THOMAS D. O'MALLEY
Treasurer




FLOYD T. CHRISTIAN
Commissioner of Education


ROBERT L. SHEVIN
Attorney General.




FRED 0. DICKINSON, JR.
Comptroller




DOYLE CONNER
Commissioner ofAgriculture


W. RANDOLPH HODGES
Executive Director








LETTER OF TRANSMITTAL


Bureau of Geology
Tallahassee
May 6, 1971


Honorable Reubin O'D. Askew, Chairman
Department of Natural Resources
Tallahassee, Florida

Dear Governor Askew:

The Bureau of Geology is publishing as its Report of Investigation, a paper,
"Seepage Beneath Hoover Dike, Southern Shore of Lake Okeechobee, Florida",
written by Mr. Frederick W. Meyer, a Geophysicist of the U.S.G.S.

The needs for the future of water in Southern Florida requires that the levee of
Lake Okeechobee be increased to obtain additional storage of water for needs of
the future. This study involved determining what the rate of seepage beneath the
dike would be when the gradient was increased across the dike.

It is anticipated that toe ditches around the levee section must be constructed in
order to control the amount of water that would be permitted to seep beneath
the dikes.

Some additional pumpage back into the lake may be required utilizing the toe
ditches as sumps.

Sincerely yours,


R.O. Vernon, Chief






















































Completed manuscript received
May 6, 1971
Printed for the Florida Department of Natural Resources
Division of Interior Resources
Bureau of Geology
by Rose Printing Company
Tallahassee, Florida

Tallahassee
1971


iv










CONTENTS

Page
Abstract ............................................................ 1
Introduction ......................................................... 1
Location of investigation .............................................. 5
Purpose and scope ................................................... 5
Methods of investigation .............................................. 6
Previous studies ..................................................... 6
Acknowledgments ................................................... 7
Geographic setting ..................................................... 8
Lake Okeechobee ................................................... 8
Topography ........................................................10
Drainage .......................................................... 10
Clim ate ........................................................... 10
Geologic setting .......................................................12
Surface deposits .................................................... 16
Subsurface deposits ..................................................16
Geohydrology ........................................................ 21
Site ..............................................................25
Description ...................................................... 25
Aquifers and confining beds ..........................................28
Water movement and fluctuations .....................................29
Quantitative Studies ................................................ 37
Seepage ....................................... .................. 40
Site 2 ....................................... ... ... ............... 44
Description ...................................................... 44
Aquifers and confining beds .................. ........................ 47
Water movement and fluctuations ..................................... 48
Quantitative studies ................................................ 54
Seepage ......................................................... 55
Site 3 ............................................................. 58
Description ...................................................... 58
Aquifers and confining beds .......................................... 59
Water movement and fluctuations ..................................... 62
Quantitative studies ................................................ 66
Seepage .......................................................... 68
Site 4 .............................................................69
Description ...................................................... 69
Aquifers and confining beds ......................................... 72
Water movement and fluctuations ..................................... 73
Quantitative studies ................................................ 78
Seepage ..........................................................79
Site 5 .............................................................80
Description ...................................................... 80
Aquifers and confining beds ......................................... 83
Water movement and fluctuations ..................................... 83
Quantitative studies ................................................ 89
Seepage ..........................................................90
Seepage along southern shore of Lake Okeechobee ............................. 91
Sum mary ............................................................ 92
References ........................................................... 95





ILLUSTRATIONS


Page


Figure
1. Map of the Lake Okeechobee area showing locations of
investigation and test sites ........................................


2- Stage-duration curve for Lake Okeechobee showing present
and future regulation ...................................
2A. Area-capacity curves for Lake Okeechobee, 1962 ..............
3. Map of Lake Okeechobee area showing topography and
principal drainage ......................................
4. Graph showing the mean monthly rainfall and temperature,
south shore of Lake Okeechobee, 1931-60 ...................
5. Graphs showing monthly rainfall and departure from the
mean monthly rainfall; monthly mean temperature and
departure from the mean monthly temperature; south shore
of Lake Okeechobee, 1963-66 ............................
6. Map of Lake Okeechobee area showing surface deposits ........
7. Map of Lake Okeechobee area showing shallow subsurface
deposits .............................................
8. Comparison of stratigraphic columns at Fort Thompson ........
9. Map showing location of site 1 near Moore Haven .............
10. Plan and profile along line A-A' showing ..................
1 I. Selected hydraulic profiles along line A-A' showing
aquifers, confining beds, and depths of observation
wells at site I .........................................
12. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 8 at site 1; and daily and
monthly rainfall at Moore Haven, 1964-65 ...................
13. Graphs comparing water levels, chloride content, and
water temperature in wells that tap aquifer A-l at site
I with data for the lake and the L-D1 Canal, 1964-65 ..........
14- Graphs comparing water levels, chloride content,
and water temperature in wells that tap aquifer A-2
at site I with data for the lake and the L-D1 Canal,
1964-65 .............................................
15. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-3 at site I
with data for the lake and the L-D I Canal, 1964-65 ............
16. Stage correlation curves for the L-DI Canal and Lake
Okeechobee for various drainage operations in the
Diston Island Drainage District ............................
17. Map showing location of site 2 near Clewiston ................
18. Plan and profile along line B-B' at site 2 ................
19. Selected hydraulic profiles along line B-B' showing
aquifers, confining beds, and depths of observation
wells at site 2 ........................................
20. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 7 at site 2: and daily
monthly rainfall at Clewiston; 1964-65 ...................


............ 4
. . . 9


............ 11


. . . .. 13




............ 14
. . . .. 17


............ 18
. . . 20
. . . .. 26
............ 27



............ 28



............ 31



. . . .. 34




............ 35



............ 36



............ 38
............ 45
............ 46



............ 47



............ 50





ILLUSTRATIONS continued


Page


Figure
21. Graphs comparing water levels, chloride content, and
water temperatures in wells that tap aquifer A-1 at
site 2 with data for the lake and the L-D2 Canal,
1964-65 ............. .................................


22. Graphs comparing water levels, chloride content, and
water temperature in wells that tap confining bed
C-2 at site 2 with data for the lake and the L-D2 Canal,
1964-65 .......................................................... 52
23. Graphs comparing water levels, chloride content, and
water temperature in wells that tap aquifer A-3 at
site 2 with data for the lake and the L-D2 Canal,
1964-65 .......................................................... 53
24. Map showing location of site 3 near Lake Harbor ........................... 59
25. Plan and profile along line C-C' at site 3 .............................. 60
26. Selected hydraulic profiles along line C-C' showing
aquifers, confining beds and depths of observation
w ells at site 3 ...................................................... 61
27. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 2 at site 3; and daily
and monthly rainfall at Clewiston; 1964-65 ............................... 64
28. Graphs comparing water levels, chloride content, and
water temperature in wells that tap aquifer A-1 at
site 3 with data for the lake and the toe ditch,
1964-65 ........................................................... 65
29. Graphs comparing water levels, chloride content and
water temperature in wells that tap confining beds
C-1 and C-2 at site 3 with data for the lake and the
toe ditch, 1964-65 .................................................. 67
30. Map showing location of site 4 near Belle Glade ............................ 70
31. Plan and profile along line D-D' at site 4 .............................. 71
32. Selected hydraulic profiles along line D-D' showing
aquifers, confining beds and depths of observation
wells at site 4 .............. .. ............. ........................ 72
33. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 1 at site 4; and daily
and monthly rainfall at Belle Glade; 1964-65 .............................. 75
34. Graphs comparing water levels, chloride content,
and water temperature in wells that tap aquifer
A-1 at site 4 with data for the lake, 1964-65 ............................... 76
35. Graphs comparing water levels, chloride content,
and water temperature in wells that tap aquifer A-2
at site 4 with data for the lake, 1964-65 .................................. 77
36. Map showing location of site 5 near Canal Point ............................ 81
37. Plan and profile along line E-E' at site 5 .............................. 82
38. Selected hydraulic profiles along line E-E' showing
aquifers, confining beds and depths of observation
wells at site 5 .............. ....................................... 84





ILLUSTRATIONS continued

Page

39- Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 2 at site 5; and daily
and monthly rainfall at Canal Point; 1964-65 .............................. 86
40- Graphs comparing water levels, chloride content, and
water temperature in wells that tap confining bed
C-I at site 5 with data for the lake 1964-65 ............................... 87
41. Graphs comparing water levels, chloride content, and
water temperature in wells that tap aquifer A-1 at
site 5 with data for the lake, 1964-65 .................................... 88






TABLES

Page
Table
1. Formations and their water-bearing characteristics
in the Lake Okeechobee area ...... ................................... 15
2. Results of slug tests at site 1 .......................................... 39
3. Results of slug tests at site 2 .......................................... 55
4. Results of slug tests at site 3 ........................................... 66
5. Results of slug tests at site 4 ....................................... 79
6. Results of seepage analyses at site 4 .................................... 79
7. Results of slug tests at site 5 .......................................... 89
8. Results of seepage analyses at site 5 ................................... 90
9. Summary of seepage beneath the Hoover Dike along the
southern shore of Lake Okeechobee .................................... 91












SEEPAGE BENEATH HOOVER DIKE,
SOUTHERN SHORE OF
LAKE OKEECHOBEE, FLORIDA

By
Frederick W. Meyer

ABSTRACT

Future water needs in southern Florida call for an increase in the storage
capacity of Lake Okeechobee. Seepage from the lake is expected to increase as a
result of raising the lake level. Data concerning the occurrence and amounts of
seepage are needed for the design and operation of flood-control works which
will remove excess water from the rich agricultural lands along the southern
shore. Intensive studies at five sites along the southern shore of Lake
Okeechobee between the Caloosahatchee Canal and the St. Lucie Canal indicate
that seepage occurs chiefly through beds of shell and limestone which underlie
the Hoover Dike at shallow depth. Seepage rates at the five sites range from
about 0.1 to 0.9 cfs per mile per foot of head across the dike. Seepage beneath
the 50-mile length of dike should increase from about 22 to 50 cfs if the average
stage of the lake is raised from 14 to 16.5 feet. Seepage is greatest between
Moore Haven and Clewiston, where deep borrows have been excavated on the
landward and lakeward sides of the dike. Most of the seepage from the lake can
be controlled by properly spaced toe ditches which would intercept the seepage
and return it to the lake.


INTRODUCTION

With the beginning of land reclamation in the Everglades at the turn of the
century, it became evident that the key to successful utilization of the rich
organic soil lay in the control of Lake Okeechobee, figure 1. In the early 1920's
attempts at flood control were undertaken by the Everglades Drainage District
and low levees were built around the southern shore of the lake to protect
nearby towns and agricultural lands from flooding. However, the attempt proved
futile, for in 1926 and 1928 hurricanes swept waters over the levees and about
two thousand people were drowned.
In 1929, the Florida Legislature created the Okeechobee Flood Control
District which overlapped and augmented the Everglades Drainage District and
efforts were made to involve the Federal Government in providing flood
protection. With the help of President Herbert Hoover, Congress adopted the
Okeechobee project under the Rivers and Harbors Act as a navigation feature






BUREAU OF GEOLOGY


81000' 80045'


/


HENDRY COUNTY


0 MILES I
EXPLANATION
M2 HGS (HURRICANE GATE STRUCTURE-2)
1aZaa HOOVER DIKE (LEVEE DI)
0 10 MILES


Figure 1. Map of the Lake Okeechobee area showing locations of
investigation and test sites.


271I5'


27o0'






REPORT OF INVESTIGATION NO. 58


with due consideration for flood control, and the U.S. Army Corps of Engineers
began work on the project in November 1930. By 1937 the Hoover Dike had
been constructed around the southern perimeter of Lake Okeechobee from
Fisheating Creek to the St. Lucie Canal.
Subsequent land reclamation in the Everglades south of Lake Okeechobee
led to overdrainage, which threatened the water supplies of the rapidly
expanding coastal cities. In 1948, Congress authorized the project "Central and
Southern Florida Project for Flood Control and Other Purposes" which, among
other things, would utilize Lake Okeechobee as a reservoir. In 1949, the State
Legislature designated the C&SFFCD (Central and Southern Florida Flood
Control District) as the agency responsible for state and local cooperation and
participation in the project. Part of the project called for increasing the storage
capacity of the lake by raising existing portions of the Hoover Dike and for
extending it around the entire shoreline. The project also called for a higher
regulation schedule for the lake.
Enlargement of the existing portions of the dike was started in 1960 and
completed in 1964. Extension of the dike around the northern perimeter is
scheduled for completion in 1970. Upon completion, the lake level (U.S. Corps
of Engineers, 1961, p.6) will be changed from that ranging between
approximately 12.5 to 15.5 feet above msl (mean sea level) to that ranging
between 15.5 and 17.5 feet above msl, figure 2. Therefore the change in
regulation would theoretically raise the average lake stage from 14 to 16.5 feet.

Seepage beneath the Hoover Dike was expected to increase as a result of
raising the lake level and agriculturists became increasingly concerned about the
effects that additional seepage would have on production in rich farmland along
the southern shore adjacent to the dike. Little was known, however, of the
existing seepage rates and the C&SFFCD and the U.S. Corps of Engineers needed
reliable data to predict the effects that raising the lake level would have on
seepage so that adequate drainage might be planned.
















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10 20


30 40 50 60 70 80 90 100


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INDICATED STAGES WERE


EXPLANATION 21
\I REGULATION __
... .. 2C
RECORD USED-DAILY AVERAGES,
OCTOBER 1940 TO SEPTEMBER 1958
--- (ADAPTED FROM KENNER, 1961) 19









12 --- ---- --- --- --- --- ------------- ^
14 -- ------- --------------- ---
--- --- --- --- -- --- -----------------,
616




12 14



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EQUALED OR EXCEEDED


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PRECENT OF TIME






REPORT OF INVESTIGATION NO. 58


LOCATION OF INVESTIGATION

The area studied is located in south central Florida along the southern
shore of Lake Okeechobee between the Caloosahatchee Canal on the west and
the St. Lucie Canal on the east (fig. 1). Intensive studies were made at the
following five sites:


Township
Site No. County (south)

1 Glades 42
2 Hendry 43
3 Palm Beach 43
4 Palm Beach 43
5 Palm Beach 41


Range
(east)


Section Levee') Station1)


33 15 D1 180+00
34 14 D2 60+18
35 36 D2 480+95
36 13 D2 980+00
37 27 D9 390+06


'U.S. Corps of Engineers base line survey.


PURPOSE AND SCOPE

In 1962, the C&SFFCD requested the U.S. Geological Survey to study the
seepage around the southern perimeter of the lake. The objective was to describe
the manner in which seepage occurred and to develop a relation between the
lake level and water levels landward of the dike, so predictions of seepage at a
lake level 2.5 feet higher than the existing level might be made.
Because the study involved about 50 miles of dike it was decided that the
estimates of seepage would be based upon detailed studies at five sites (fig. 1),
on the premise that they would be representative of the average hydraulic
conditions. The length of dike that was assumed to be represented by each site is
as follows:


Site No.

1
2
3
4


Length of Dike (miles)

9.0
8.5
8.5
10.0
14.0






BUREAU OF GEOLOGY


Field studies began in the fall of 1963 and ran concurrently with the
raising of the dike and re-routing of U.S. Highway 27 along the landward toe of
the dike between Clewiston and South Bay. As a result of the construction the
progress of the study was impeded and field work continued until the spring of
1966. During the period December 1967 through March 1968 verification tests
were performed at site 1 near Moore Haven at the request of C&SFFCD and the
U.S. Sugar Corporation. The results of those tests (Meyer, 1969) confirmed
seepage data collected during the period 1963-66.


METHODS OF INVESTIGATION

Observation wells were drilled in a line perpendicular to the dike at each
site in order to determine the extent, thickness, and character of the subsurface
materials and to define the hydraulic gradients. The wells ranged from about 4
to 50 feet deep and were constructed of either 2- or 4-inch diameter steel casing.
Measuring points were established at each observation well to reference changes
in water-levels. Fluctuations of ground-water levels on the landward side of the
Hoover Dike were continuously recorded in at least one observation well at each
of the 5 sites.
Observation points (OP's) were established in nearby canals and in the lake
to reference changes in surface-water levels. Fluctuations in the stage of Lake
Okeechobee were continuously recorded at HGS 3 (Hurricane Gate Structure 3)
at Lake Harbor and at HGS 5 at Canal Point.
Data concerning water levels, chloride content of water, and water
temperature were collected at monthly intervals. Hydrologic profiles were
constructed from these data to analyze ground-water movement (seepage)
relative to the stage of the lake. Aquifer coefficients were determined by
pumping tests, slug tests, and/or by relating seepage gains or losses in canals to
hydraulic gradients.
Wells used in this report were numbered consecutively at each site and are
cross referenced to a county numbering system and a national numbering
system. Observation points (OP's) in the lake and canals were numbered
consecutively.

PREVIOUS STUDIES

No detailed studies of seepage along the southern shore of Lake
Okeechobee were made prior to this study. However, the U.S. Corps of
Engineers (1963, p. 10) estimated that the seepage from Lake Okeechobee into
the L-D1 Borrow Canal, located at site 1 near Moore Haven, would be about
12-7 cfs (cubic feet per second) per mile, per foot of head between the lake and
the canal. The Corps (1953) estimated the seepage through similar strata at four






REPORT OF INVESTIGATION NO. 58


sites along the alignments of proposed levees remote from the Hoover Dike.
Seepage for test sites 6, 7, 9, and 10 ranged from about 0.5 to 3 cfs per mile of
levee, per foot of head across the base of the proposed levees. However, the
width of the proposed levees was about half that of the Hoover Dike, therefore,
the rates of seepage under a levee equivalent in size to the Hoover Dike would be
about half the estimated rates.
Schroeder, Milliken and Love (1954, p. 12-14) reported that the
transmissivity of a sand and shell aquifer at Delray Beach, in eastern Palm Beach
County, was about 70,000 gpd/ft (gallons per day per foot). Similar aquifers
occur at shallow depth in the vicinity of Lake Okeechobee.
Parker, Ferguson, Love, and others (1955) described the geomorphology,
geology, and general hydrology of the Everglades including Lake Okeechobee.
They reported that the hydraulic conductivity(permeability) of terrace sands at
the north end of the lake ranged from 10 to 800 gpd/ft2 (gallons per day per
square foot) and might exceed 3,000 gpd/ft2 in well-sorted sand. Studies made
by the U.S. Geological Survey in cooperation with the Soil Conservation Service
indicated that there was no substantial gain or loss by the lake through
underground flow (op. cit., p. 107, 185), that the permeability of organic soils is
low (op. cit., p. 109), and that areas of low permeability generally have water of
poor quality (op. cit., p. 183-184).
Water-budget studies of Lake Okeechobee by Langbein (op. cit., p.
551-560) suggest that as much as 6 inches, or 250,000 acre-ft. could have been
lost annually, from the lake by seepage. However, Langbein concluded that the
apparent 6-inch loss was probably due to an error in the pan coefficient used in
computing evaporation.
Other studies relating to the hydrogeology of the area were made by
Greene (1966); Klein, Schroeder, and Lichtler (1964); Kenner (1961); Lichtler
(1960); Matson and Sanford (1913); Meyer and Hull (1969); Parker (1942);
Stringfield (1933); and the U.S. Corps of Engineers (1955, 1961, 1962, 1963).
Studies pertaining to the geology of the area were made by Cooke (1945); Dall
(1887, 1893); Dubar (1958); Heilprin (1887); Mansfield (1931a, 1931b, 1939);
Olsson (1964); Parker (1944); Perkins (1968); Puri and Vernon (1964); Roland
(1969); and Schroeder, Millikin, and Love (1954). Historical information on the
hydrology of the area is presented in reports by Herr (1943), Wallis (1942), and
Jones (1948).

ACKNOWLEDGMENTS

This report was prepared by the U.S. Geological Survey as part of the
cooperative water resources program with the Central and Southern Florida
Flood Control District and the U.S. Corps of Engineers. The investigation was
conducted under the direct supervision of Howard Klein, former subdistrict





BUREAU OF GEOLOGY


chief, Water Resources Division, Miami, Florida, and under the general
supervision of C.S. Conover, district chief, Water Resources Division,
Tallahassee, Florida.
The author thanks the following people for assistance rendered during the
investigation: Messrs. W. V. Storch and R. L. Taylor of the Central and Southern
Florida Flood Control District; Messrs. J. J. Koperski, 0. G. Rawls, Angelo
Tabita, J. H. Grimes, and A. R. Broadfoot of the U. S. Corps of Engineers; Mr.
C. W. Knecht of the U. S. Sugar Corporation; Mr. J. D. Rogers of the Pahokee
Drainage District; Mr. W. M. Jeffries of South Florida Conservacy District; Dr. D.
R. Moore, paleontologist of the Institute of Marine Science, University of Miami;
and Dr. A. A. Olsson, retired consulting geologist of Coral Gables, Florida.



GEOGRAPHIC SETTING


LAKE OKEECHOBEE


Lake Okeechobee, in the southern part of the Florida Peninsula (fig. 1), is
the second largest fresh-water lake wholly within the conterminous United
States. The lake includes parts of Glades, Hendry, Martin, Okeechobee, and Palm
Beach Counties. It is nearly circular, measuring about 35 miles from north to
south and about 30 miles from east to west. The shoreline, approximately 105
miles long, is rimmed by the Hoover Dike. The surface area of the lake, including
three small islands, is about 680 square miles (4.35 million acres) at average stage
of 14 feet above msl as shown by the area-capacity curves on figure 2A. The
average depth is 7 feet and the maximum depth is about 15 feet at average stage.
Approximately 3.5 million acre-ft (acre-feet) of fresh water are stored in the lake
at average stage 14 feet (fig. 2A). The useable storage between 10.5 and 15.5
feet is about 2 million acre-ft of which 0.6 million are used annually for
irrigation. Future water needs, however, call for increasing the storage capacity
of the lake by raising the average stage from 14 to about 16.5 feet, which will
increase both the average storage capacity and the useable storage (between 10.5
and 17.5 feet) by about a million acre-ft.
The lake water is generally hard and highly colored. The total dissolved
solids in the water seldom exceeds 300 mg/1 (milligrams per liter). The
temperature of the water ranges from 60F (160C) in the winter to about 90F
(32C) in the summer. A few municipalities and industries use the lake as a
source of water supply.
The lake is chiefly used as a flood-control storage basin for excess waters
and for irrigation of the large sugar plantations, truck farms, and cattle ranches






REPORT OF INVESTIGATION NO. 58


AREA,THOUSAND ACRES
520 480 440 400 360 320 280 240 200 160 120 80 40 0


CAPACITY, MILLION ACRE-FEET


Figure 2A. Area-capacity curves for Lake Okeechobee, 1962.








that surround the lake. It is also used for cross-state navigation, commercial
fishing, and recreation. Water from the lake also replenises supplies to the
growing coastal cities.





BUREAU OF GEOLOGY


TOPOGRAPHY

The most prominent topographic feature in southern Florida is the
Everglades-Lake Okeechobee basin (Davis, 1943, p. 41). Lake Okeechobee, which
lies at the northern extent of the basin, is a shallow saucer-like depression within
the broad flat plain. The deepest point in the lake is slightly below sea-level, fig-
ure 3. The northern half of the lake is almost completely surrounded by sandy
prairies that range in altitude from 20 to 30 feet above msl. The southern half of
the lake lies in the Everglades where the altitude of land surface ranges from 14
to 20 feet above msl.
Studies by Stephens (1951) indicated that the surface of the Everglades
agricultural area had subsided several feet due chiefly to drainage and resultant
shrinkage of organic soils. He reported (op. cit. p. 13) that during 1912-1950 the
average thickness of organic soils in the upper Evergaldes had shrunk about 40
percent, at an average rate of about one foot in ten years. Thus the altitude of
land surface in the agricultural area, prior to reclamation, was about 18 to 20
feet above msL.

DRAINAGE

Runoff from about 5,650 square miles drains southward into the lake.
Largest of the inflowing streams is the Kissimmee River (fig 3) which discharges
about 1.6 million acre-feet (0.5 cubic mile) into the lake annually. Other
principal inflowing streams or canals are Fisheating Creek, the Harney Pond and
Indian Prairie Canals, Taylor Creek, and Nubbin Slough.
The principal canals that drain the lake are the Caloosahatchee and St.
Lucie which together with the lake comprise the Okeechobee Waterway inland
navigation route between the Gulf of Mexico and the Atlantic Ocean. Other
large canals that drain the lake are the Hillsboro, North New River, West Palm
Beach, and Miami, which are also used for routing excess water during the rainy
season into the lake by back-pumping from the agricultural area.
In pristine times the natural flow from the lake was chiefly southward
through the Everglades but some flow occurred westward through the
Caloosahatchee Swamp. Parker, Ferguson, Love, and others (1955, p. 332)
estimated that overflow occurred at stage 15 feet and reached sizeable
proportions between stages 17 and 18 feet.

CLIMATE

The climate of the Lake Okeechobee region is subtropical and is
characterized by warm, humid summers and moderately cool winters.
Climatological data presented herein are based on the mean of data collected by





REPORT OF INVESTIGATION NO. 58


81000' 80045'

2701-- HIGHLANDS 'A OKEECHOBEE COUNTY ST. LUCIE
COUNT OKE HOB a COUNTY -




S OUNTY D MARTIN



y/ PORT
2700d K CHOBE YA















HENDRY2645HABO S
OOR WISTO o







V EVERGLADES
HENHDRY COUNTY SOUTH










0 10 MILES
Figure 3. Map of Lake Okeechobee area showing topography and principal
drainage.





BUREAU OF GEOLOGY


the U. S. Weather Bureau at Moore Haven Lock 1 and Belle Glade Experiment
Station. The average annual rainfall during 1931-1960 was 54.50 inches. Rainfall
is seasonal with about 75 percent of the yearly total occurring during May
through October. Mean monthly rainfall ranges from 1.56 inches in December to
8.46 inches in September, figure 4. The maximum daily rainfall recorded at the
Belle Glade Experiment Station was 10.90 inches in November 1931, and the
maximum monthly rainfall there was 24.11 inches in June 1945. Rainfall during
1963-65, figure 5, was below normal despite severe weather conditions that
accompanied the passage of three hurricanes. On August 27, 1964, Hurricane
Cleo passed a few miles east of Lake Okeechobee. Winds associated with Cleo
ranged from 80 mph on the east shore to 40 mph on the west shore. Rainfall
during the period August 27-28 was 1.89 inches at Belle Glade and 0.68 inch at
Moore Haven. On October 14, 1964, Hurricane Isabell, a small but wet
hurricane, passed a few miles southeast of the lake; 5.09 inches of rainfall were
measured at Belle Glade and 0.50 inch was measured at Moore Haven. On
September 8, 1965, Hurricane Betsy crossed the southern tip of Florida; and
rainfall for September 8-9 was 2.08 inches at Belle Glade and 1.99 inches at
Moore Haven.
Rainfall during 1966 was above average. Hurricane Alma skirted the west
coast of Florida during June 8-9 dumping 3.01 inches of rain at Belle Glade and
3.12 inches of rain at Moore Haven.

The average annual temperature during 1931-1960 was 72.70F. Mean
monthly temperatures ranged from 63.30F in January to 81.10F in August (fig.
5). Killing frosts occur infrequently. The lowest temperature recorded at Belle
Glade was 24F in January 1940 and the highest was 100oF in July 1931.
Temperatures were slightly below normal during 1963 and 1966 but were
slightly above normal during 1964 and 1965 (fig. 5).


GEOLOGIC SETTING

The Lake Okeechobee area lies within the Coastal Lowlands of Florida
(Cooke, 1939, p. 14). The Lake Okeechobee-Everglades basin probably was a
shallow embayment, or depression, formed on an ancient sea floor during, or
prior to, Pleistocene time. Seas covered the area during the Pleistocene
interglacial stages and marine calcareous materials were deposited. During glacial
stages the seas retreated and the area was eroded, but fresh-water marls were
deposited in shallow depressions. The Lake Okeecobee-Everglades basin
probably was a lake or a swamp during a part of each glacial stage.
The formations1 that underlie the area at shallow (less than 50 feet) depth
range from Miocene to the Holocene in age as shown in table 1. The oscillations





BUREAU OF GEOLOGY


chief, Water Resources Division, Miami, Florida, and under the general
supervision of C.S. Conover, district chief, Water Resources Division,
Tallahassee, Florida.
The author thanks the following people for assistance rendered during the
investigation: Messrs. W. V. Storch and R. L. Taylor of the Central and Southern
Florida Flood Control District; Messrs. J. J. Koperski, 0. G. Rawls, Angelo
Tabita, J. H. Grimes, and A. R. Broadfoot of the U. S. Corps of Engineers; Mr.
C. W. Knecht of the U. S. Sugar Corporation; Mr. J. D. Rogers of the Pahokee
Drainage District; Mr. W. M. Jeffries of South Florida Conservacy District; Dr. D.
R. Moore, paleontologist of the Institute of Marine Science, University of Miami;
and Dr. A. A. Olsson, retired consulting geologist of Coral Gables, Florida.



GEOGRAPHIC SETTING


LAKE OKEECHOBEE


Lake Okeechobee, in the southern part of the Florida Peninsula (fig. 1), is
the second largest fresh-water lake wholly within the conterminous United
States. The lake includes parts of Glades, Hendry, Martin, Okeechobee, and Palm
Beach Counties. It is nearly circular, measuring about 35 miles from north to
south and about 30 miles from east to west. The shoreline, approximately 105
miles long, is rimmed by the Hoover Dike. The surface area of the lake, including
three small islands, is about 680 square miles (4.35 million acres) at average stage
of 14 feet above msl as shown by the area-capacity curves on figure 2A. The
average depth is 7 feet and the maximum depth is about 15 feet at average stage.
Approximately 3.5 million acre-ft (acre-feet) of fresh water are stored in the lake
at average stage 14 feet (fig. 2A). The useable storage between 10.5 and 15.5
feet is about 2 million acre-ft of which 0.6 million are used annually for
irrigation. Future water needs, however, call for increasing the storage capacity
of the lake by raising the average stage from 14 to about 16.5 feet, which will
increase both the average storage capacity and the useable storage (between 10.5
and 17.5 feet) by about a million acre-ft.
The lake water is generally hard and highly colored. The total dissolved
solids in the water seldom exceeds 300 mg/1 (milligrams per liter). The
temperature of the water ranges from 60F (160C) in the winter to about 90F
(32C) in the summer. A few municipalities and industries use the lake as a
source of water supply.
The lake is chiefly used as a flood-control storage basin for excess waters
and for irrigation of the large sugar plantations, truck farms, and cattle ranches









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TABLE 1. FORMATIONS AND THEIR WATER-BEARING CHARACTERISTICS IN THE LAKE OKEECHOBEE AREA.

Series Formation1) Range in thickness Lithology Water-bearing property
____(feet)

Holocene Organic soil 0-10 Peat. Low permeability.

Lake Flirt Marl 0-10 Sandy marl. Low permeability.
Pleistocene
Terrace deposits 0-10 Quartz sand. Low permeability.

Fort Thompson
Formation 0-30 Alternating marine and Variable permeability; low in dense
fresh-water limestones crystalline limestones and high in
and/or marls. shelly limestone.





Caloosahatchee Marl 0-30 Shell, sand, clay, and Variable permeability; high in shell
sandy limestone, beds and low in clay.




Miocene Tamiami Formation 30-110 Clay, sand, and sandy Variable permeability; high in sand-
limestone. stone beds and low in sands and clay.




1) The nomenclature and stratigraphy used herein are based on that used by the Florida Geological Survey (Puri and Vernon, 1964).





BUREAU OF GEOLOGY


the U. S. Weather Bureau at Moore Haven Lock 1 and Belle Glade Experiment
Station. The average annual rainfall during 1931-1960 was 54.50 inches. Rainfall
is seasonal with about 75 percent of the yearly total occurring during May
through October. Mean monthly rainfall ranges from 1.56 inches in December to
8.46 inches in September, figure 4. The maximum daily rainfall recorded at the
Belle Glade Experiment Station was 10.90 inches in November 1931, and the
maximum monthly rainfall there was 24.11 inches in June 1945. Rainfall during
1963-65, figure 5, was below normal despite severe weather conditions that
accompanied the passage of three hurricanes. On August 27, 1964, Hurricane
Cleo passed a few miles east of Lake Okeechobee. Winds associated with Cleo
ranged from 80 mph on the east shore to 40 mph on the west shore. Rainfall
during the period August 27-28 was 1.89 inches at Belle Glade and 0.68 inch at
Moore Haven. On October 14, 1964, Hurricane Isabell, a small but wet
hurricane, passed a few miles southeast of the lake; 5.09 inches of rainfall were
measured at Belle Glade and 0.50 inch was measured at Moore Haven. On
September 8, 1965, Hurricane Betsy crossed the southern tip of Florida; and
rainfall for September 8-9 was 2.08 inches at Belle Glade and 1.99 inches at
Moore Haven.
Rainfall during 1966 was above average. Hurricane Alma skirted the west
coast of Florida during June 8-9 dumping 3.01 inches of rain at Belle Glade and
3.12 inches of rain at Moore Haven.

The average annual temperature during 1931-1960 was 72.70F. Mean
monthly temperatures ranged from 63.30F in January to 81.10F in August (fig.
5). Killing frosts occur infrequently. The lowest temperature recorded at Belle
Glade was 24F in January 1940 and the highest was 100oF in July 1931.
Temperatures were slightly below normal during 1963 and 1966 but were
slightly above normal during 1964 and 1965 (fig. 5).


GEOLOGIC SETTING

The Lake Okeechobee area lies within the Coastal Lowlands of Florida
(Cooke, 1939, p. 14). The Lake Okeechobee-Everglades basin probably was a
shallow embayment, or depression, formed on an ancient sea floor during, or
prior to, Pleistocene time. Seas covered the area during the Pleistocene
interglacial stages and marine calcareous materials were deposited. During glacial
stages the seas retreated and the area was eroded, but fresh-water marls were
deposited in shallow depressions. The Lake Okeecobee-Everglades basin
probably was a lake or a swamp during a part of each glacial stage.
The formations1 that underlie the area at shallow (less than 50 feet) depth
range from Miocene to the Holocene in age as shown in table 1. The oscillations





BUREAU OF GEOLOGY


of sea level are permanently recorded by alternating marine and fresh-water
strata. The shallow geology is complex due to relatively rapid depositional and
environmental changes. Consequently, few geologists agree on the ages of the
shallow formations.

The nomenclature and stratigraphy used herein are based on that used by the
Florida Geological Survey (Puri and Vernon, 1964).



SURFACE DEPOSITS

Surface deposits include organic soil, which is chiefly comprised of peat
that accumulated in the Lake Okeechobee-Everglades basin during Holocene
time, and sand of late Pleistocene-Holocene age. Figure 6 shows the type and
distribution of surface deposits in the Lake Okeechobee area. Parker, Ferguson,
Love and others (1955, p. 109) reported that samples of peat from depths
ranging from 5 to 6 feet in the upper Everglades were determined to be about
5,000 years old by Carbon 14 dating. In 1945, the organic soil ranged in
thickness from 8 feet on the southeastern side of the lake to a feather edge on
the southwestern side.
Sand that mantles the area on the north, east, and west sides of the lake is
probably part of the Pamlico Formation of late Pleistocene age. This sand,
probably not more than 10 feet thick, was derived from the higher Terrace
deposits when sea level was about 25 feet higher than present sea level. The sand
has been classified by the U. S. Soil Conservation Service as being poorly-drained
or well-drained. The well-drained sand occupies areas of slightly higher
topography suggesting that the drainage characteristic is related to topographic
position rather than to the permeability of the sand.



SUBSURFACE DEPOSITS

Underlying the surface deposits are beds of shell, clay, marl, and sand,
which range from Miocene through Pleistocene in age. These beds are referred to
herein as subsurface deposits and their distribution is shown in figure 7.
The Tamiami Formation (Parker, 1951, p. 823), of Miocene age, is
composed of silty shelly sands and silty shelly marls that occasionally contain
thin beds of limestone or sandstone. Schroeder and Klein (1954, fig. 5) reported
that the top of the formation lies at a depth of about 60 feet in the Belle Glade
area- Klein, Schroeder, and Lichtler (1964, Table 3) reported that the Tamiami
occurs at depth of about 35 feet near Moore Haven and that the formation






REPORT OF INVESTIGATION NO. 58


81000'


80045'


27 15' -


-HOOVER DIKE


/


LAKE,
I


EXPLANATION
ORGANIC SOIL


C LESS THA
E3 3-5 FEET
[I 5-8 FEET
B MORE THA
FI NE
0 WELL DRA


N 3 FEET


N 8 FEET
SAND
INED


POORLY DRAINED


260o4


DISTRICT


IOMILES


Figure 6. Map of Lake Okeechobee area showing surface deposits.


OKEECHOBEE


2700'





BUREAU OF GEOLOGY


aood


LAKE


80*45'


/
/7
/
OKEECHOBEE


FORT THOMPSON NAL
FORMATION POINT
0E
IER DIKE CALOOSAHATCHEE
OU MARL ASO:


FORMATION

.. .. ..

H.mARBOR BELEi6
O U N T Y :..:.::i:i..:::i"


. .


AFTER PURl AND VERNON 1964, PLATE 2C
0 10 MILES
l ________


Figure 7. Map of Lake Okeechobee area showing shallow subsurface deposits.


27 l5'


26 45





REPORT OF INVESTIGATION NO. 58


ranges from 30 to 110 feet thick. Puri and Vernon (1964, plate 2C) mapped a
small patch of green clay which occurs near the surface on the northwest side of
the lake as the Tamiami (see fig. 7). Klein, Schroeder, and Lichtler (1964, p.26),
however, included a similar bed of clay in the overlying Caloosahatchee Marl
because it seemed to be restricted to the flanks of eroded hills of the Tamiami.
During this study the top of the Tamiami Formation was located by test
drilling at a depth of about 40 feet at sites 1 and 2 near Moore Haven and
Clewiston, respectively. The Tamiami is chiefly composed of fine to very coarse
quartz sand with some limestone, sandstone, and phosphate. Principal fossils
found in the Tamiami are Balanus sp., Cymatosyrinx lunata Dall, Ringincula sp.,
Hanetia (Solenosteira) mengeana (Dall), and Nassarius (Uzita) bidentata
(Emmons). A bed of green clay occurs in the overlying Caloosahatchee Marl.
The Caloosahatchee Marl (Dall, 1887) unconformably overlies the Tamiami
Formation. The formation underlies the surface deposits in much of the area
surrounding the northeastern, northwestern, and southwestern shores of the
lake; and underlies the younger Fort Thompson Formation in the area beneath
the lake and southeastward thereof (fig. 7). The Caloosahatchee Mairl is
composed chiefly of shelly sand and shelly sandy marl and an occasional bed of
limestone. DuBar (1958, p.35) assigned the Caloosahatchee to the Pleistocene
and reported a maximum thickness of about 50 feet. However, the formation
generally ranges between 15 and 30 feet thick in the study area. The fossils
contained in the formation are too numerous to list here but Cyprea problematic
is generally considered to be a good index fossil. DuBar (op. cit.) reported that
the Caloosahatchee Marl cropped out in a small area between Moore Haven and
Clewiston. The same area was mapped by Parker (1955) as Fort Thompson.
The Fort Thompson Formation (Cooke, 1929, p. 211-215) is composed of
alternating beds of fresh-water and marine marls and/or fresh-water and marine
limestone. The formation does not exceed 30 feet in thickness and underlies
most of the lake. The formation is unconformable to beds above and below. The
most common fossil in the fresh-water beds is Helisoma scalare.
After intensive studies of the type localities of the Caloosahatchee Marl
and the Fort Thompson Formation, DuBar (1958) assigned the Caloosahatchee
Marl to the Pleistocene Series rather than the Pliocene Series primarily on the
basis of vertebrate fossils, and to a lesser degree on mollusks and stratigraphic
relationship. Most investigators have accepted DuBar's biozonation but not all
agree on the age of the Caloosahatchee.
Figure 8 is a comparison of the stratigraphic columns of principal
investigators at the type locality of Fort Thompson located 21 miles west of
Moore Haven on the Caloosahatchee River. Parker (1955) presented the
stratigraphy at Fort Thompson originally proposed by Parker and Cooke (1944).
DuBar (1958) mapped the biozones along the Caloosahatchee River, subdivided
the Caloosahatchee Marl and the Fort Thompson Formation into members,

















I,
0




a
U
H
p
0


Ii
p


PARKER (1955) DUNAR I1956) BROOkS (1965) OL80N (1"4)

8 a d S *
S8TRATA I MEMBER MEMBER FORMATION

^---** ----- ----- ^- -------- ---------
PAMLICO 7 P
SAND 7 PAMLICO

COFFEE MILL COFFEE MILL COFFEE MILL w
HAMMOCK 6 U HAMMOCK 6
MEMBER I HAMMOCK FORMATION z
FRESH WATER C""
z LIMESTONE 5 z
AND MARL 0 a FORT
S MARINE SHELL > 5 A THOMPSON
8 f (EgI sP.) 4 5 a O NALOANOOC1HE _
o FRESH WATER a
MARL AND 3 se s
LIMESTONE w
4L AYERS LANDING lil
MARINE SHELLS 2 B UNIT A
_________ BEE BRANCH BEE BRANCH
z IL
w w -

I., .,uo | 0 || 0 ,u | C
S MARINE SHELLS I FORT i
DENAUD o DENAUD
-L -0 -





REPORT OF INVESTIGATION NO. 58


assigned the Fort Thompson Formation and the Caloosahatchee Marl to the
Pleistocene and included the lower part of the Fort Thompson Formation in the
Caloosahatchee Marl. Olsson (1964) assigned the Caloosahatchee Marl to upper
Miocene and assigned the lower part of the Fort Thompson to "Unit A" of
Pliocene age. Brooks (1968) included the lower part of the Fort Thompson
Formation in the Caloosahatchee Marl, reassigned the Caloosahatchee Marl to
Pliocene and lower Pleistocene, retained part of DuBar's subdivision of the
Caloosahatchee Marl and part of Parker's original Fort Thompson Formation,
and upgraded the Coffee Mill Hammock Member to a formational rank.
However, DuBar's stratigraphic designations are presently recognized and used
by the Florida Geological Survey (Puri, and Vernon 1964, p.232).
Terrace deposits, which are composed chiefly of quartz sand, underlie the
surface deposits in a band across the northernmost part of the lake (fig. 7).
These deposits are only a few feet thick and are pre-Pamlico (Pleistocene) in age.


GEOHYDROLOGY

This study is principally concerned with the source, direction and rate of
seepage through the materials underlying the Hoover Dike and to a lesser extent
with the quality of the water. Test drilling at each of the five sites yielded data
on the depth, thickness, lithology, and hydraulic characteristics of aquifers
(permeable strata) and of confining beds (relatively impermeable strata). In some
cases it was difficult to identify separate aquifers because differences in
lithologies and in permeabilities were not pronounced. However, measurements
of water levels and their fluctuations in selected observation wells yielded the
data needed to prepare hydraulic profiles (flow nets) that ultimately aided in the
identification of aquifers and confining beds and of points of recharge and
discharge.
The hydraulic profiles of the five sites were generally similar in that
seepage from the lake initially moved inland from a deep borrow (the Navigation
Canal) in the lake. Seepage moved through a filtercake, which lined the borrow,
into an aquifer (or aquifers) underlying the Hoover Dike toward discharge
points, such as canals and ditches, where water levels were controlled at
optimum levels for farming. Water-level fluctuations indicated that steady-state
flow from the lake to discharge points in the nearby agricultural areas was
usually attained within a few days after periods of unsteady water levels.
Therefore, the steady-state seepage from the lake may be reasonably estimated
by using the hydraulic gradients during periods of relatively stable water levels.

During steady-state conditions, the seepage from the lake is equivalent to
the flow through the filtercake and the flow through the aquifers beneath the
dike. At those sites where the filtercake is missing, or has about the same





BUREAU OF GEOLOGY


permeability as the continuous aquifers, the seepage from the lake is about
equivalent to the flow through the aquifers.
Obviously it would have been difficult to determine the flow through the
filtercake because of the difficulty in obtaining data from the deep borrow
(Navigation Canal) in the lake. On the other hand it was relatively easy to
determine the flow through the aquifers underlying the dike at each. site. Once
the hydraulic characteristics of the aquifer(s) and the average hydraulic gradient
in the aquifers were determined, it was possible to compute the amount of
seepage from the lake through each aquifer using the modified form of the
Darcy equation.
Q=TIL (1)

where Q is the seepage in gallons per day, T is the transmissivity of the aquifer in
gallons per day per foot, I is the average hydraulic gradient (steady state) in the
aquifer; and L is the length of dike or, canal, along which T was effective. The
gradient, I, was determined by the equation

I=h (2)
I=--
d
where h is the head, in feet, between the steady-state water levels, hence
equipotential lines, in two observation wells in the same aquifer, and d is the
distance, in feet, between the wells.
The hydraulic characteristics of the aquifers were determined by relating
observed water-level fluctuations caused by natural or artificial discharge and
recharge to suitable equations. The characteristics are commonly referred to as
transmissivity and hydraulic conductivity (field). Transmissivity, T, is the rate of
flow, in gallons per day, at the prevailing water temperature, through a vertical
strip of aquifer, 1 foot wide having a height equal to the saturated thickness, m,
of the aquifer, under a unit hydraulic gradient. Hydraulic conductivity (field),
Kf, is the rate of flow, in gallons per day, at the prevailing temperature, through
a one square foot section of aquifer under a unit hydraulic gradient. If T is
known, Kf may be determined by dividing T by the thickness of the aquifer (m).
Conversely, if Kf is known, T may be determined by multiplying Kf by the
thickness of the aquifer (m).
Pumping tests and slug tests were performed on selected wells in order to
determine the transmissivity of the various aquifers. The pumping test
(nonequilibrium) method involved pumping a well at a constant rate and
recording the rate of drawdown or recovery in the pumped well and/or in nearby
observation wells. The slug test (nonequilibrium) method involved injecting a
known volume of water (a slug) into an observation well and recording the rate
of decline of head in the well. The data were subsequently analyzed to
determine T using standard methods presented in reports by Ferris and others
(1962) and by Cooper, Bredehoeft, and Papadapulos (1967).





REPORT OF INVESTIGATION NO. 58


Seepage tests were also used to determine T whenever it was possible to
relate measured seepage into or out of a canal to hydraulic gradients in aquifers.
Generally, the method involved measuring the discharge entering or leaving a
specified reach of canal at the landward toe of the Hoover Dike and then relating
the discharge to ground-water gradients which were determined by water-level
measurements (equipotential lines) in the line of observation wells normal to the
dike at the respective site.
The analysis of the test data depended upon the following conditions: 1)
that the transmissivity and the gradients were uniform along the reach of the
canal affecting the seepage, and 2) that the seepage tests had continued for
sufficient time for the waters levels to stabilize, or to reach a steady state.
Under steady state conditions, the measured discharge leaving or entering
the reach of canal. Qc, is related to the seepage by the equation

Qc = Q +Qa-E (3)

where Q1 is the seepage from or into the lake, Qa is the seepage from or into the
agricultural area, and E is the loss imposed by evaporation.
Actually, none of the seepage tests continued long enough for water levels
to stabilize completely. Therefore part of the measured flow (Qc) was caused by
changes in both canal and ground-water storage. Thus compensation for change
in storage is expressed in the equation

Qc = Qi + Qa +ASc +ASg E (4)
where ASc is the change in canal storage and ASg is the change in ground-water
storage; and both terms are expressed in terms of daily mean discharge. Elements
Qc, Qi, Qa, ASc, and ASg are positive when, 1) seepage is toward the canal,
2) discharge is leaving the reach of canal, and 3) water levels in the canal and
aquifers are falling.
The seepage tests, however, were continued sufficiently long that the
magnitude of the terms E and ASg became very small in relation to other terms
and they were dropped from the equation. Thus the following equation was used
to determine the approximate seepage relationship for a steady state condition.

Qc = Qi + Qa +ASc (5)
Equations 6 and 7 below are expressions of steady state seepage related to
the lake and agricultural area, where I is the hydraulic gradient related to the
lake and Ia is that related to the agricultural area.
Qr =TLI1 (6)


Qa = TLIa






BUREAU OF GEOLOGY


Equation 8 below is obtained by substituting equations 6 and 7 in
equation 5; and equation 9 is obtained by solving equation 8 in terms of T.

Qc = TL(I + Ia) + ASc (8)

T Qc ASc (9)
L(II + la)


Usually the data collected during seepage tests were concerned with the
terms on the right hand side of equation 9. Once the transmissivity of the
aquifer (s) was determined it was possible to determine the lake seepage (Q1)
associated with hydraulic gradients beneath the Hoover Dike using equation 6.
Because a single aquifer test is merely a guidepost to aquifer transmissivity,
several tests were usually performed at each site in order to obtain values of
transmissivity that were consistent with the geologic and hydrologic setting.
Once the proper magnitude of seepage (Qi) was determined at each site it
was possible to relate the value to the hydraulic gradient across the Hoover Dike
because a linear relationship exists between the gradient across the dike and the
gradient in the aquifer(s) beneath the dike during steady-state conditions. For
convenience, seepage (Qt) is expressed in terms of a seepage factor, Se, which is
defined herein as the steady-state rate of seepage per length of recharge section
per foot of head between the recharge boundary and the discharge boundary. It
is determined by using the equation

Se = i (10)
L(h hc)

where Q, is the seepage rate expressed in cubic feet per second (cfs), L is the
length of the recharge section in miles, h, is the elevation of the water level at
the recharge boundary in feet, and hc is the elevation of the water level at the
discharge boundary in feet.
In most cases the lakeside Navigation Canal was considered the recharge
boundary and the landside borrow canal, or toe ditch, was considered the
discharge boundary. However, in places that lacked a close, well-defined
discharge boundary on the landward side of the dike, the seepage factor was
related to the lake level and the ground-water level in an observation well located
at the landside toe of the dike. In the latter case the seepage factor was related
to the head between the lake and a specific point in the aquifer (the well); and
future estimates of seepage using the seepage factor (Se) will require a
knowledge of the steady-state water level in the well. Therefore, it would be
advantageous to retain those wells as permanent observation wells.






REPORT OF INVESTIGATION NO. 58


The value of the seepage factor for each site can be expected to decrease in
the future as the filtercake continues to form in the lakeside borrows but there
are insufficient data at present to determine the rate of reduction in the seepage
factor. However, effects of the filter-cake buildup may be determined in the
future by comparing the seepage computed using the seepage factor with the
seepage determined by gradients in aquifer(s) beneath the dike. Therefore,
long-term water-level data are needed at each site to detect future changes in
seepage factors.
Measurements of chloride content and temperature of both surface and
ground water were used to supplement the hydraulic data. The chloride content
of water in shallow aquifers beneath the southern shore of the lake is in many
places high (Parker, 1955, p. 818 and Klein, 1964, p. 73), whereas the chloride
content in lake waters is relatively low. Thus, high chloride content in aquifers
that underlie the dike would indicate that the aquifers convey relatively little
seepage from the lake; whereas low chloride content in the aquifers would
indicate that they convey significant amounts of seepage from the lake.
Temperature variations were also helpful in determining zones which convey
seepage from the lake.
Because the geohydrology at each of the sites is somewhat different, the
sites will be discussed separately in the sections that follow.

SITE 1


DESCRIPTION

Site 1 is in Glades County on the southwest shore of Lake Okeechobee
about 5 miles east of Moore Haven, as shown in figure 9. The site consists of
data collection stations along a line about 820 feet long, which constructed
normal to the Hoover Dike, as shown by figure 10. The stations consist of 19
test wells, of which 14 were used to obtain data on ground-water levels. Two
observation points (OP's) were used to obtain water-level data in the lake and in
the L-Dl Canal. North of the dike is the Navigation Canal which was excavated in
the thirties to construct the Hoover Dike. South of the dike is the L-D1 Canal
which was excavated in 1962 to raise the dike to its present height (39 feet
above mean sea level) and to construct a smaller dike along the southern
(landward) bank of the L-DI Canal.
Natural land surface at the site is about 13 feet above msl
and is underlain by about 2 to 3 feet of organic soil (see profile in fig. 10). The
area south of the LD1 Canal is devoted chiefly to agriculture (sugar cane) and
water levels there are controlled by the Diston Island Drainage District. The
district is drained by a series of north-south lateral canals (not shown in fig. 9)






BUREAU OF GEOLOGY


EXPLANATION
PROPOSED PUMP STATION
PUMP
-- CITY BOUNDARY

Figure 9. Map showing location of site 1 near Moore Haven.


about 25 feet wide and 5 feet deep. The lateral canals are spaced at half-mile
intervals and connect to main canals which are about 60 feet wide and 7 feet
deep. The main canals are equipped with pumping facilities and gated controls to
provide drainage and to route water from the lake for irrigation.
At site I the flow of a 3W-mile reach of the L-DI Borrow Canal is regulated
by automatic flap gates on two 72-inch culverts (culverts IB and IC in fig. 9) at
the intersection with the main pump pools near culverts 1 and 1A. The flap gates
on culverts I B and IC close when the water level in the pump pool is higher than
that in the borrow canal. The flap gates are usually closed during the rainy
season when the Diston Island Drainage District pumps into the lake. The flap






REPORT OF INVESTIGATION NO. 58


>" I EXPLANATION

; IN I If *. WELL
!eso- ? -. liei a OBSERVATIOM POINTr
,I RIGHT- I-WAY LMN

-200 0 200 400
RANGE,FEET
A PLAN
4o'-
HOOVER DIKE LAKE
3d- FILL fine to coarse sand; and
shell.
[ SOIL organic black; and some
2 *I sand.
2L-D CNAL SILT organic black; and fine
sand.
@ LDSTONE tan, hard, sandy,
10 with some shell.
U SHELL tan to white, sandy,
marly.
EA L SAND quartz, fine to medium,
with phosphate and shell.
Q SHELL brown to gray, Ostrea sp.
id- SHELL gray to white, large and
small mollusks.
.....- g SHRELL white, chiefly Turritella sp.
2 CLAY green, sandy with phosphate
S- and Fontitens sp.
0 SAND quarts, fine to very coarse,
3 with phosphate and mica;
.. and sandy limestone with
-200 6 200 400 barnacles.
RANGE,FEET
PROFILE
(STATION 180)
Figure 10. Plan and profile along line A-A' at site 1.

gates are usually open during the dry seasons when the seepage from the lake
into the L-DI Canal supplements the regulated flow of irrigation water from the
lake through culvert 1 A into the district.
The profile along line A-A' at site 1 (fig. 10) shows that the materials to a
depth of about 32 feet below msl are sand, marl, shell, and limestone which
grade laterally and vertically into each other. Generally beds of limestone and
shell are considered aquifers and beds of marl, fine sand, and clay are considered
confining beds. Seepage is greatest through shell beds within the Caloosahatchee
Marl, which ranges between 10 feet above msl to 20 feet below msl.







A,
JANUARY 13, 1965


8.
JUNE 3,1965


C,
OCTOBER 12, 1965


SOUTH


i


















I'


Mj DIKE
CONFINING BED DISCUSSED
IN TEXT BY NUMBER
rrI AOUIFER DISCUSSED IN
TEXT BY NUMBER
,2 EOUIPOTENTIAL LINEVALUE IS
FEET ABOVE MEAN SEA LEVEL


==, DIRECTION OF FLOW
-so ISOCHLOR VALUE IS
MILLIGRAMS PER LITER
6 WELL NUMBER AND
UNCASED PORTION


RANGE,FEET
EXPLANATION


to
I?>















rQ

0 0-
dl9






REPORT OF INVESTIGATION NO. 58


numbered consecutively with increasing depth, and the numbers are peculiar
only to site 1.
Confining bed C-1 is composed of relatively impermeable black organic
soil. The bed retards the movement of water between the surface and the
underlying beds, but its confining ability is locally ineffective where the bed is
cut by many canals and ditches. Aquifer A-1 is chiefly a sandy marly limestone.
The upper surface of the bed is well cemented and relatively impermeable,
however, locally occurring solution holes account for zones of high permeability,
Confining bed C-2 is composed of shelly sand. The bed is only slightly less
permeable than the overlying aquifer but it probably contains zones of very low
permeability. Aquifer A-2 is chiefly shell and is highly permeable. Confining bed
C-3 is composed of green clay and it is relatively impermeable. Aquifer A-3 is
composed of sand and sandstone and it is moderately permeable.
Some seepage occurs through all the beds but most seepage occurs through
aquifers A-1, A-2, and A-3. However, aquifers A-i and A-2 and perhaps
confining bed C-2 are the chief sources of seepage from the lake because they are
breached by deep borrow canals on the lakeward and landward sides of the dike.
The Navigation Canal is the perennial recharge boundary. The L-DI Canal is the
chief dry season discharge boundary and the network of ditches in the fields
nearby is the chief wet season discharge boundary.
Silt deposits that line the sides and bottoms of the borrow canals play an
important part in seepage. These deposits were formed chiefly by the settling of
the fine fractions from the excavated material and by the accumulation of
organic sediments derived from dead vegetation and the erosion of nearby
surface materials. Because the level of the lake is usually higher than the water
level in the Diston Island Drainage District, hydrostatic pressure has probably
caused these deposits to form a filtercake on the bottom and walls of the
Navigation Canal; and the buildup of the filtercake probably has caused a
progressive reduction in the rate of seepage from the lake over the years. The
loss in head across the filtercake is an important factor in analyzing aquifer
coefficients because more head is required to move water at a given rate through
the filtercake than to move water at the same rate through a like thickness of
aquifer. Therefore, the determination of seepage through an aquifer must be
related to the transmissivity and hydraulic gradients within the aquifer itself, and
not to gradients which include the head across the filtercake.

WATER MOVEMENT AND FLUCTUATIONS

The principal direction of water movement at site 1 is from Lake
Okeechobee to the Diston Island Drainage District as shown in the hydraulic
profiles (fig. 11) by the arrows representing flow lines. Short seasonal reversals
occur however when the stage of the lake is routinely lowered prior to the rainy





REPORT OF INVESTIGATION NO. 58


assigned the Fort Thompson Formation and the Caloosahatchee Marl to the
Pleistocene and included the lower part of the Fort Thompson Formation in the
Caloosahatchee Marl. Olsson (1964) assigned the Caloosahatchee Marl to upper
Miocene and assigned the lower part of the Fort Thompson to "Unit A" of
Pliocene age. Brooks (1968) included the lower part of the Fort Thompson
Formation in the Caloosahatchee Marl, reassigned the Caloosahatchee Marl to
Pliocene and lower Pleistocene, retained part of DuBar's subdivision of the
Caloosahatchee Marl and part of Parker's original Fort Thompson Formation,
and upgraded the Coffee Mill Hammock Member to a formational rank.
However, DuBar's stratigraphic designations are presently recognized and used
by the Florida Geological Survey (Puri, and Vernon 1964, p.232).
Terrace deposits, which are composed chiefly of quartz sand, underlie the
surface deposits in a band across the northernmost part of the lake (fig. 7).
These deposits are only a few feet thick and are pre-Pamlico (Pleistocene) in age.


GEOHYDROLOGY

This study is principally concerned with the source, direction and rate of
seepage through the materials underlying the Hoover Dike and to a lesser extent
with the quality of the water. Test drilling at each of the five sites yielded data
on the depth, thickness, lithology, and hydraulic characteristics of aquifers
(permeable strata) and of confining beds (relatively impermeable strata). In some
cases it was difficult to identify separate aquifers because differences in
lithologies and in permeabilities were not pronounced. However, measurements
of water levels and their fluctuations in selected observation wells yielded the
data needed to prepare hydraulic profiles (flow nets) that ultimately aided in the
identification of aquifers and confining beds and of points of recharge and
discharge.
The hydraulic profiles of the five sites were generally similar in that
seepage from the lake initially moved inland from a deep borrow (the Navigation
Canal) in the lake. Seepage moved through a filtercake, which lined the borrow,
into an aquifer (or aquifers) underlying the Hoover Dike toward discharge
points, such as canals and ditches, where water levels were controlled at
optimum levels for farming. Water-level fluctuations indicated that steady-state
flow from the lake to discharge points in the nearby agricultural areas was
usually attained within a few days after periods of unsteady water levels.
Therefore, the steady-state seepage from the lake may be reasonably estimated
by using the hydraulic gradients during periods of relatively stable water levels.

During steady-state conditions, the seepage from the lake is equivalent to
the flow through the filtercake and the flow through the aquifers beneath the
dike. At those sites where the filtercake is missing, or has about the same






30 BUREAU OF GEOLOGY


season. Profiles A-C were constructed from data collected on January 13, 1965,
June 3, 1965, and October 12, 1965, respectively, to show the distribution of
equipotential lines and chloride content for selected high and low stages of the
lake. Although the profiles depict the instantaneous conditions of flow normal
to the Hoover Dike, that is, along a stream line, the equipotential lines generally
represent the steady state hydraulic gradients in the flow system.
On January 13, 1965, a period of high water levels, the stage of Lake
Okeechobee at the Navigation Canal was 14.18 feet and the stage of the L-Dl
Canal was 11.69 feet. The principal direction of water movement in aquifers A-1
and A-2 was from the Navigation Canal to the L-DI Canal. The principal
direction of water movement in aquifer A-3 was southward toward an
undetermined point of discharge in the Diston Island Drainage District, but some
upward movement probably occurred through confining bed C-3. in the area
immediately south of the L-DI Canal. Most of the seepage occurred through
aquifers A-I and A-2. Of the measured 10.5 cfs discharging through culvert 1C
from the 3-.mile reach of the L-DI Canal, about 7.5 cfs -was estimated to have
seeped from the lake. The close, even spacing of equipotential lines and the low
chloride content in aquifers A-1 and A-2 beneath the Hoover Dike suggests that
locally the upper 25 to 30 feet of strata act as a unit aquifer. The high chloride
content in water in aquifer A-3 suggested that relatively little water seeped from
the lake through that unit.
On June 3, 1965, a period of low water levels, the stage of Lake
Okeechobee at the Navigation Canal was 12.44 feet, the stage of the L-DI Canal
was 12.09 feet, and the principal direction of ground-water movement in
aquifers A-I, A-2, and A-3 was from the Navigation Canal into the Diston Island
Drainage District. No losses occurred from the L-DI Canal other than seepage
and evaporation. Hydraulic gradients were low indicating that the rate of seepage
was lower than it was on January 13, 1965.
On October 12, 1965, a period of high water level, the stage of Lake
Okeechobee at the Navigation Canal was 14.37 feet and the stage of the L-DI
Canal was 1432 feet. About 8.5 cfs was flowing from the lake through culvert 1
into the 3%-mile reach of the L-D1 Canal because of a malfunction of culvert 1B
after the passing of Hurricane Betsy in September. This condition caused a
landward shift in the principal recharge boundary from the Navigation Canal to
the L-DI Canal, which resulted in a significant decrease in the chloride content in
aquifer waters beneath the L-D1 Canal.
A comparison of the daily mean stage of the lake with the daily highest
water level in well 8, on figure 12, shows that during 1964-65 the stage of the
lake was higher than the stage of the water level in well 8 except for a few days
in June 1965. Fluctuations of the lake level are chiefly caused by seiche, winds,
seasonal rainfall on the basin, and water-management practices of the nearby
drainage districts and the U. S. Corps of Engineers. Fluctuations of the water







REPORT OF INVESTIGATION NO. 58


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


( HURRICANE
) HURRICANE
( HURRICANE


EXPLANATION

CLEO C4
ISABELL (5
BETSY


IRRIGATION EFFECT
PUMPING EFFECT


Figure 12. Graphs showing daily stages of Lake Okeechobee and ground-
water levels in well 8 at site 1; and daily and monthly rainfall at
Moore Haven, 1964-65.


level in well 8 are chiefly caused by fluctuations of the water level in the L-DI
Canal which is presently controlled by the water-management practices of the
Diston Island Drainage District.

Water-level fluctuations in the lake that generally lasted only a few days
were usually caused by winds. In some instances short-term peaks (waves), such
as those caused by hurricanes or low waves from large boats, were transmitted


4 255 480 061 067 234 520 476 889 346 274 065 072

2- | 60
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BUREAU OF GEOLOGY


through aquifer A-1 and were recorded in well 8. The location of well 8 is such
that its water level is closely related to the water level in the L-DI Borrow Canal.
The water level in the L-DI Canal is controlled by two 6-foot gated culverts (lB
and IC) which connect to the pump bays at culverts 1 and 1A (see locations on
fig. 9). The water levels in the pump bays are in turn controlled by gates on
culverts 1 and I A, which lead to the lake, and by rectangular concrete controls
with removable stop logs, which lead from the pump bays to the main canals of
the Diston Island Drainage District.
When the district needs water from the lake for irrigation during dry
periods, the gates on culverts 1 and 1A are partly opened and the stop logs in the
controls are removed, thereby allowing water to flow from the lake into the
district. This operation causes the automatic flap gates in culverts lB and IC to
open, allowing water to drain from the L-Dl Canal into the pump bays until the
level in the L-DI Canal reaches a level slightly above that in the pump bays, or
until the level in the L-Dl Canal falls below the bottom invert of culverts 1B and
I C (invert elevation 10.2 feet).
When the district needs to remove excess water from the fields after heavy
rains the stop logs are replaced in the controls, the gates on culverts 1 and 1A are
opened, and water is pumped from the main canals into the lake. This operation
causes the water levels in the pump bays to exceed that in the L-DI Canal,
thereby closing the automatic flap gates in culverts 1B and IC. Then the water
level in the L-DI Canal rises to a static level between the lake level and the water
level in the district.
Thus, the peaks on the hydrograph of well 8 (fig. 12) during 1964 usually
represented periods when the district was pumping excess water into the lake
and the troughs usually represented periods when the district was withdrawing
irrigation water from the lake.
During April and May, 1965, the U. S. Corps of Engineers routinely
lowered the stage of Lake Okeechobee and the regional water level to about 12
feet above msl prior to the wet season (fig. 12). After heavy rains in early June,
water levels in the district rose above the lake level and reverse seepage, that is
seepage from the district to the lake, occurred for a few days. After a normal
landward gradient was reestablished, the gates on culverts IB and 1C were closed
due to pumping from the district to the lake and the water levels in well 8 (and
in the L-DI Canal) rose to a level between the lake level and the water level in the
district.
On September 11, 1965, shortly after the passing of Hurricane Betsy,
some debris became lodged under the automatic flap gate at culvert 1B,
permitting water to flow from the lake through culvert 1 (which was open) and
culvert IB into the L-DI Canal, and the water level in well 8 (and in the L-D1
Canal) approached that of the lake (fig. 12). If no water was seeping from the
-DI Canal into the district, then the water levels in the L-DI Canal and well 8






REPORT OF INVESTIGATION NO. 58


would have equalled that of the lakes and the flow into the L-Dl Canal would
have ceased. However, the water level in well 8 (and in the L-D1 Canal) was lower
than the lake level. Therefore, it follows that water was seeping from the L-D1
Canal into the district and the flow through culvert lB represented the seepage
losses along the 3-mile reach from culvert 1B to culvert 1C, assuming that
evaporation losses were insignificant. This condition existed through December,
1965, and the inland shift in the distribution of flow is shown by the hydraulic
profile on October 12, 1965, in figure 11. Thus operations of the landside
drainage works in the Diston Island Drainage District has a significant effect on
the relationships between the stage of the lake and the stage of the L-DI Canal,
the hydraulic gradients from the lake, and the seepage from the lake.
Figures 13 through 15 are graphs comparing water levels, chloride content,
and water temperature in wells that tap the three aquifers with data for the lake
and the L-D1 Canal. The lines representing the well data are coded by numbers
of dots; the line with the least dots represents the well nearest the lake.
A comparison of the data in figures 13 and 14 suggest that locally aquifers
A-1 and A-2 are hydraulically connected and function as a unit aquifer. The data
in figure 15 suggest that confing bed C-3 separates aquifer A-3 from the
shallower aquifers. The data in figures 13 and 14 also indicate that near the dike
water levels in aquifers A-1 and A-2 are highly influenced by the operational
stage of the L-D1 Canal. Of particular importance is the fact that most of the time
the water levels in the wells 5, 10, and 11 were closely related to fluctuations in
the water levels in the L-Dl Canal despite their close proximity to the recharge
boundary (the Navigation Canal). This relationship suggest that the head loss
between the lake and the water levels in the nearby wells is caused by a layer of
silt, or a filtercake, on the walls of the lakeside Navigation Canal.
Generally, waters in the lake, the L-Dl Canal, and in aquifers A-1 and A-2,
contained chloride concentrations ranging between 50 and 100 mg/1 (milligrams
per liter) as shown on figures 13 and 14. Chloride content was slightly lower in
the wells farthest from the lake suggesting that aquifers A-1 and A-2 were
recharged by local rainfall as well as by seepage from the lake.
Waters in aquifer A-3 (fig. 15) contained chloride concentrations ranging
from 100 to more than 800 mg/1. Concentrations in aquifer A-3 were lowest in
the area near the Navigation Canal where infiltration of fresh water from the
lake was greatest. Concentrations were highest in the district south of the L-Dl
Canal, which suggests that seepage through aquifer A-3 from the lake into the
district is of minor importance.
However, infiltration from the L-Dl Canal into aquifer A-3 was induced by
pumping nearby well 14 (fig 15). The chloride content in well 3 decreased from
about 800 mg/1 in February 1965 to 500 mg/1 in April 1965 after well 14 was
pumped at a rate of about 80 gpm (gallons per minute) on March 4. In August
1965, well 14 was again pumped and the water in well 3 was freshened to about







BUREAU OF GEOLOGY


M J J A S O N DIJ F MA M J JA S 0 N D
1964 EXPLANATION 1965 "


-LAKE --- WELL 8


- L-DI CANAL
---WELL 5


.-.- WELL 6
.--- WELL 12


Figure 13. Graphs comparing water levels, chloride content and water
temperature in wells that tap aquifer A-I at site 1 with data for
the lake and the L-D1 Canal, 1964-65.


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REPORT OF INVESTIGATION NO. 58


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J F M A M J JASONDJF M A M J J A S ND
1964 19.65
EXPLANATION


- LAKE
- L-DI CANAL
-- WELL 10


-..- WELL 7
WELL 9
.-.- WELL 13


Figure 14. Graphs comparing water levels, chloride content and water
temperature in wells that tap aquifer A-2 at site 1 with data for
the lake and the L-DI Canal, 1964-65.


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BUREAU OF GEOLOGY


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1964 1965
EXPLANATION


- L-DI CANAL
---LAKE
--- WELL II


Figure 15. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-3 at site 1 with data for
the lake and the L-D1 Canal, 1964-65.


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REPORT OF INVESTIGATION NO. 58


500 mg/1. Well 3 was further freshened to less than 300 mg/1 after the
malfunction of culvert lB during Hurrican Betsy in September 1965, which
caused the recharge boundary to shift from the Navigation Canal to the L-DI
Canal.
The temperature (OF) of water in the L-D1 Canal and in the lake side
Navigation Canal ranged from the high sixties during the winter to high eighties
during the summer. The seasonal variation in temperature of ground water
decreased with depth. Temperatures in aquifer A-3 were least affected by
seasonal variations in temperature.
During 1964-65, monthly observations of water levels and of operations of
the drainage works at site 1 suggested that three generalized relations could be
recognized between the stages of the lake and the L-DI Canal. Monthly
measurements of the stages in the lake were plotted against the stages in the L-Dl
Canal, figure 16, and the plots were then related to the physical operations of the
drainage works. The first line (1) represents the relationship caused by the
malfunction of culvert IB and the resultant shift in the recharge boundary from
the Navigation Canal to the L-Dl Canal. The second line (2) represents the
approximate relationship that occurs when the L-Dl Canal is ponded by
pumping operations. The third line (3) represents the relationship when the L-D1
Canal is draining into the Diston Island Drainage District during irrigation
operations. Because seepage from the lake is closely related to the head between
the lake and the L-Dl Canal, the relationship in line 2 can be used to estimate
water levels in the L-Dl Canal when the canal is ponded by operations of the
drainage works during wet periods if no physical changes occur in the system.

QUANTITATIVE STUDIES

Aquifer tests were performed at site 1 to determine the transmissivity (T)
and/or the hydraulic conductivity (K) of the aquifers which are the chief
conveyers of seepage from the lake. Pumping tests were conducted on wells 9
and 10 which tap aquifer A-2, and on well 3 which taps aquifer A-3 (see
locations of wells on profile in fig. 11A).
Well 9 was pumped for 60 minutes at a rate of 90 gpm while water-level
fluctuations were recorded in wells 3, 6, 7, 10, 13, and in the pumped well (9).
Well 10 was pumped for 40 minutes at a rate of 122 gpm while fluctuations of
water levels were recorded in wells 5, 7, 8, and 11. The data indicated that
recharge from the L-DI Canal, from the Navigation Canal and from vertical
leakage, caused me arawdowns in the observation wells to be suppressed early in
the tests. However, an analysis of a few data which were collected early in the
tests and therefore least affected by recharge, suggests that the value of T could
be in the magnitude of 100,000 gpd/ft. The tests also indicated that locally beds
A-1, C-2 are essentially a unit aquifer, that water flows from the borrow canals






BUREAU OF GEOLOGY


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Okeechobee for various drainage operations in the Diston Island
Drainage District.





into the aquifers A-1 and A-2, and that some leakage (minor amounts) occurs
through bed C-3.

Well 3 was pumped for 62 minutes at a rate of 12% gpm while fluctuations
of water levels were recorded in wells 11 and 14, and in the pumped well. The


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REPORT OF INVESTIGATION NO. 58 39


data suggest that the transmissivity of aquifer A-3 in about 7,000 gpd/ft and that
some leakage occurs through confining end C-3.
Slug tests were conducted in wells 1 through 3 at 9 different zones during
drilling operations. The results of the slug tests are presented in table 2. The
analysis of the slug tests generally required a great deal of subjective judgement,
therefore the results only suggest the magnitude of values that might be
expected. The estimated value of T for the saturated zone of flow beneath the
dike between 13.5 feet above msl and 17 feet below msl is about 28,500 gpd/ft;
and that for the zone between 17 and 31 feet below msl is about 6,900 gpd/ft.
Probably the minimum T value that might be expected for the total flow zone
would be about 35,000 gpd/ft.


TABLE 2. RESULTS OF SLUG TESTS AT SITE 1.
Thickness Kf T
Bed (feet) (gpd/ft2) (gpd/ft)

Dike Fill 31 20 60
C-1 1 2 2
A-1 '5 1,2001 6,0002
C-2 3 70 210
A-2 18.5 1,200 22,200
C-3 6 20 120
A-3 8 850 6,800
TOTAL 44.5 35,392

1 Saturated
2 Estimated


On January 13, 1965 a seepage test was conducted in the 3-mile reach of
the L-D1 Canal between culverts 1B and 1C (see location on fig. 9). Water levels
were measured in the observation wells and at observation points at site 1 in
order to relate hydraulic gradients to the measured discharge (10.5 cfs) flowing
eastward from the L-DI Canal through culvert 1 C. The waterlevel data were used
to construct the hydraulic profile at site 1 (see profile A in figure 11) and the
hydraulic gradients at site 1 were assumed to be uniform along the L-DI Canal
from culvert 1B to culvert 1C. Culvert IB was closed, so that the flow through
culvert 1C represented most of the seepage from the lake to the L-DI Canal.
Seepage from the lake was assumed to have reached a steady-state condition
because the water level in well 8 (thus the stage of the L-DI Canal) had
stabilized for a period of at least 2 weeks prior to the test (fig. 12). The





BUREAU OF GEOLOGY


transmissitivity along the 3Wmile reach was assumed to be uniform because
geologic conditions along the reach (U. S. Corps of Engineers 1961, plate 13) are
similar to those at site 1, therefore, the hydraulic gradient between wells 10 and
7 was assumed to be representative of the gradient across the aquifer beneath the
Hoover Dike along the reach. The hydraulic gradient, Ii, between wells 10 and 7
was determined by equation 2.

h 0.71 foot
=11 = 0.00355
d 200 feet
The hydraulic gradient across the aquifer from the L-DI Canal southward to the
Diston Island Drainage District was almost flat at site 1, therefore the I was
assumed to be zero.
Transmissivity, T, was computed using equation 9.

Qg ASp
T =L (11 a)
where Qc was the measured discharge from the L-Dl Canal at culvert IC, 10.5 cfs
(6.8 mgd); ASc was determined to be equivalent to 1.7 cfs (1.1 mgd); L was
18,800 feet; It was 0.00355; and la was assumed to be an insignificant factor.

6.8 mgd- 1.1 mgd
T 18,800 ft (0.00355) + 18,800 ft (0.00000)

T = 85,400 gpd/ft

Thus, the transmissivity of the strata that convey the seepage from the
lake was estimated to be about 85,400 gpd/ft; and the value of T obtained by
the seepage test was considered to be more representative of the actual T than
those obtained by the pumping tests and the slug tests.
In 1968, however, three additional seepage tests were conducted at site 1
at the request of the C&SFFCD in order to verify the results of the January 13th
test. Test 3 (Meyer, 1969, p. 20-26) involved the lowering of the water level in
the 3W-mle reach of the L-DI Canal several feet below the lake level by
pumping; and the results of test 3 suggested that the transmissivity of the
water-bearing strata beneath the dike was about 64,600 gpd/ft. However, the
results of the three tests indicated that T is probably about 72,300 gpd/ft (op.
cit., p. 27); therefore, the value 72,300 gpd/ft was used to compute seepage at
site 1.
SEEPAGE

Seepage from the lake at site 1 can be estimated using the transmissivity of
the water-bearing strata that underlie the dike and the hydraulic gradient






REPORT OF INVESTIGATION NO. 58


between wells 10 and 7. On the other hand, it would be more convenient to
estimate the seepage using the water levels in the lake and the L-D1 Canal, but
the loss in head across the filtercake on the walls of the Navigation Canal
prevents a direct computation of seepage from the lake (Q1) using equations 6
or 9, and the aquifer transmissivity. However, a comparison of water-level data
indicated that there is a direct relationship between the water levels in wells 10
and 7 and the water levels in the lake and the L-D1 Canal. Therefore, the seepage
through the aquifer(s) can be related directly to the head between the lake and
the LD1 Canal by using equation 10, assuming that the relationships will not
change appreciably in the future due to the slow buildup of the filtercake.
The seepage factor, Se, was therefore computed using equation 10 and the
data for the seepage test on January 13, 1965. The length of canal section (L)
was 18,800 feet, or 3.56 miles; the seepage pickup (Q1) was assumed to be 8.8
cfs; the stage of the lake (hi) was 14.18 feet; and the stage of the L-D1 Canal
(hc) was 11.69 feet.

Q_ 8.8 cfs
L(hi hc) 3.56 mi. (14.18 ft. 11.69 ft.)

= 1.0 cfs/mi/ft


Thus, the seepage factor, Se, at site 1 was estimated to be about 1.0 cfs per mile
per foot of head between the lake and the L-D1 Canal; and this value was
considered representative for design purposes.
On the basis of the 1968 tests, the seepage for the test on January 13,
1965, was re-evaluated using. 72,300 gpd/ft as the value of T. Equation 9 was
used to evaluate the gradients related to the seepage into the L-DI Canal.

72,300 Igpdft= 6.8 mgd 1.1 mgd
72,300 gpd/ft 18,800 ft. (0.00355 + Ia)

la = 0.00064
The result suggested that some seepage was derived from the Diston Island
Drainage District. Equation 7 was used to determine the amount that seeped
from the district into the L-DI Canal.

Qa = 72,300 gpd/ft x 0.00064 x 18,800 ft.

= 0.87 mgd or 1.3 cfs

Thus the earlier assumption that the gradient la on the south side of the canal
was equal to zero was erroneous, and a net 1.3 cfs seeped from the district into






BUREAU OF GEOLOGY


the L-DI Canal along the 3V2-mile reach. This condition was later confirmed by
test 2 of the 1968 tests.
On the basis of the 1968 value of T, the distribution of seepage during the
test on January 13, 1965, was re-evaluated using equation 5.

Qc= Q +Qa+ASc
10.5 cfs = 7.5 cfs + 1.3 cfs + 1.7 cfs
10.5 cfs = 10.5 cfs

Thus, the seepage from the lake (Q1) was about 7.5 cfs and not 8.8 cfs as
originally determined.
The seepage factor (Se) was recomputed using equation 10, where Q1 is
7.5 cfs, L is 3.56 miles, he (lake) is 14.18 feet, and he (L-D1 Canal) is 11.69 feet.

Qi
e L(h -hc)


Se = 7.5 cfs
3.56 mi (14.18 ft. 11.69 ft.)

Se = 0.8 cfs/mi/ft.


Thus the seepage factor (Se) for the January 13, 1965 test is about 0.8 cfs per
mile per foot of head between the stage of the lake and that of the L-DI Canal;
and the results of the January 13 test are within the order of magnitude of both
the original estimate which was used for design purposes and the average value of
0.9 cfs/mi/ft which was determined by the 1968 tests. However, the 1968 value
is considered the more reliable of the three values. Therefore, the seepage factor
(Se) at site 1 is about 0.9 cfs per mile per foot of head between the stage of Lake
Okeechobee and that of the L-DI Canal.
The present effect of the filtercake in the Navigation Canal is included in
the value of the seepage factor but the value can be expected to decrease as the
filtercake continues to build up and the lake level is raised. The data suggest that
the filtercake causes a 68 percent reduction in seepage from the lake. If the
filtercake has formed uniformly since the excavation of the Navigation Canal in
the early thirties then the buildup of the filtercake has reduced the seepage
about 2 percent per year, however, there are no data to support this conclusion.
Therefore no attempt was made to relate the seepage factor to future changes in
the filtercake, but it is apparent that the value of the seepage factor will decrease
in the future.
Seepage from the lake into the Diston Island Drainage District is related to
the lake level and the operational water levels of the district and the L-D1 Canal.






REPORT OF INVESTIGATION NO. 58


If the average stage in the L-D1 Canal were maintained at, or slightly below, the
average stage of water table in the Diston Island Drainage District then the L-Dl
Canal would intercept most of the seepage from the lake. For example, if the
average stage of the L-DI Canal were maintained at about 11.0 feet (that is below
the average stage in the district).by pumping the seepage back into the lake, then
the average annual rate of seepage into the L-D1 Canal would be the product of
the seepage factor (0.9 cfs/mi/ft) and the average head between the lake and the
L-D1 Canal (14 ft. 11 ft. = 3 ft), or 2.7 cfs per mile. If the average stage of the
lake were raised to 16.5 feet then the average rate of seepage into the L-DI Canal
would be about 5.0 cfs per mile. If the L-D1 Canal were ponded, that is, closed
off at both ends, then the seepage would pass from the lake through the canal
southward into the Diston Island Drainage District; and the seepage would be
approximately proportional to the head between the lake and the L-D1 Canal.
For example, if the culverts at the ends of the L-DI Canal were closed so that the
canal were ponded, then the stage of the canal that would correspond to an
average lake stage of 14 feet would be about 12.8 feet (from line 2 in figure 16);
and the corresponding average rate of seepage into the Diston Island Drainage
District would be about 1.1 cfs per mile (1.2 ft x 0.9 cfs/mi/ft). If the average
stage of the lake were increased to 16.5 feet then the average stage of the L-D1
Canal would be 14.1 feet and the average seepage to the Diston Island Drainage
District would be about 2.2 cfs per mile.

In order to estimate the average increase in seepage that would result from
raising the average stage of the lake from 14 to 16.5 feet, one would have to
know the long-term water levels in the L-DI Canal and in the District. The only
data available, however, were those collected during 1964-65, but they suggest
that the long-term water levels in the L-Dl Canal and the adjacent fields are
regulated slightly below 11.5 feet during the dry (irrigation) season, and that the
aforementioned water levels are regulated slightly above 12 feet during the wet
season. If it is assumed that the future regulation of the water levels will be the
same, that is, drainage operations will occur 50 percent of the time and irrigation
operations will occur the other 50 percent, then it is possible to estimate the
increase in seepage that will result from raising the average stage of the lake.

During the 1964 dry season, most of the seepage from the lake was
intercepted by the L-D1 Canal, which discharged the seepage southward into the
Diston Island Drainage District. The water level in the L-D1 Canal was controlled
at a stage of about 11.5 feet by the irrigation practices of the Diston Island
Drainage District regardless of the stage in the lake. Therefore, during irrigation
periods; the long-term average head between the lake and the L-DI Canal is
estimated to be about 2.5 feet (14 ft 11.5 ft = 2.5 ft) and the resultant seepage
is about 2.2 cfs per mile (2.5 ft x 0.9 cfs/mi/ft). If the average stage of the lake is
raised to 16.5 feet, the average head should be about 5.0 feet and the resultant
seepage should be about 4.5 cfs per mile.






BUREAU OF GEOLOGY


During the 1964 wet season, the drainage practices of the Diston Island
Drainage District usually caused the water in the L-DI Canal to pond. When the
average stage of the lake is 14 feet, the average stage of the L-DI Canal is about
12.8 feet. Therefore, during the wet seasons the long-term average gradient
between the lake and the L-Dl Canal is estimated to be about 1.2 feet and the
resultant seepage is about 1.1 cfs per mile. If the average stage of the lake is
raised to 16.5 feet, then the average stage of the L-Dl Canal will rise to 14.1 feet
and the average seepage will be about 2.2. cfs per mile. If the irrigation and
drainage seasons are about equal in duration, then the average annual seepage
rates are about 1.6 and 3.4 cfs per mile for the corresponding average lake stages
of 14 and 16.5 feet and the average increase in seepage will be about 1.8 efs per
mile.
Thus, raising the average stage of Lake Okeechobee from 14 feet to 16.5
feet should increase the average seepage rate at site 1 from 1.6 to 3.4 cfs per mile;
and the seepage beneath the 9-mile section of dike represented by site 1 should
increase from 14.4 to 30.6 cfs.

SITE 2

DESCRIPTION

Site 2 is located in Hendry County on the southwestern shore of Lake
Okeechobee about 1 mile east of Clewiston as shown on Figure 17. The site
consists of data-collection stations along a line about 470 feet long, which was
constructed normal to the Hoover Dike, as shown in plain view of figure 18. The
data-collection stations include 16 test wells, of which 11 were used to obtain
data on ground-water levels, and two observation points (OP's) which were used
to obtain data on water-levels in the lake and in the L-D2 Canal.

North of the Hoover Dike is the Navigation Canal which was used in the
early thirties for borrow to construct the dike. South of the Hoover Dike is the
L-D2 Canal from which borrow was taken in 1962 to raise the dike to its present
height. The L-D2 Canal is about 9,700 feet long and is not connected to the
flood control works in the agricultural area or to the Industrial Canal at
Clewiston, just south of the L-D2 Canal on U.S. Highway 27 which parallels the
length of the canal. Beyond U. S. Highway 27 the land is locally uncultivated
and poorly drained. The nearest controlled drainage at site 2 is located in the
agricultural area about one quarter mile south of the dike. Canals in the
agricultural area, which are equipped with pumping facilities and gated controls,
provide drainage during wet periods and route water from the lake for irrigation
during dry periods. Water levels in the agricultural area are locally regulated by
the Clewiston Drainage District.








REPORT OF INVESTIGATION NO. 58


EXPLANATION
PROPOSED PUMP STATION
PUMP
--- CITY BOUNDARY


Figure 17. Map showing location of site 2 near Clewiston.


Natural land surface at site 2 ranges from 14 to 15 feet above msl and it is
underlain by about a foot of organic soil (see profile in fig. 18). Beneath the soil
are beds of sand, limestone, marl, clay, and shell which grade vertically and
laterally into each other. Generally beds of shell and limestone are permeable
and beds of organic soil, sand, marl and clay are relatively impermeable. Seepage
is probably greatest through solution holes in the limestone which ranges from 4
to 12 feet (above msl) in what appears to be the upper part of the







BUREAU OF GEOLOGY


PLAN


om


z
MJ


RANGE,FEET


0 200 400
RANGE, FEET
PROFILE
(STATION 60+18)


EXPLANATION
e WELL
OBSERVATION POINT
RIGHT-OF-WAY LINE
=--= ROAD
B-B' LINE OF PROFILE




3 FILL fine quartz sand and shell
SOIL organic black; and some
sand.
[j SILT organic black; and fine
sand.
[] SAND quartz, medium to fine;
with some shells.
g LIMESTONE white to light
gray, hard to soft,
very sandy, with some
shell and phosphate.
MARL white to light gray,
-very sandy.
[] SAND quartz, very fine to
very coarse, with some
fine phosphate.
j SHELL white to tan, sandy,
mostly micromollusks.
CLAY green, sandy, shelly,
with phosphate.
j SANDSTONE grading into sandy
limestone.
E SAND quartz fine to very
coarse.


Figure 18. Plan and profile along line B-B' at site 2.



Caloosahatchee Marl. Permeable beds of shell, which range from 8 to 27 feet
below msl in the lower part of what also appears to be Caloosahatchee Marl, are
potential conveyers of large amounts of seepage if penetrated by deep borrow
canals on the landward and lakeward sides of the dike.






REPORT OF INVESTIGATION NO. 58


AQUIFERS AND CONFINING BEDS


The aquifers, confining
B-B' at site 2, are shown on


beds, and depths of observation wells along line
figure 19A. The aquifers and confining beds are


A.
JANUARY 14, 1965
B
40'i


B.
JUNE 3, 1965


C.
OCTOBER 12, 1965


RANGE, FEET
EXPLANATION
4-= DIRECTION OF FLOW


i CONFINING BED DISCUSSED
IN TEXT BY NUMBER
i AQUIFER DISCUSSED IN
I TEXT BY NUMBER


-80- ISOCHLOR VALUE IS
MILLIGRAMS PER LITER
1 WELL NUMBER AND
UNCASED PORTION


EQUIPOTENTIAL LINE,VALUE IS
FEET ABOVE MEAN SEA LEVEL





Figure 19. Selected hydraulic profiles along line B-B' showing aquifers,
confining beds and depths of observation wells at site 2.


DIKE






BUREAU OF GEOLOGY


numbered consecutively with increasing depth and the unit numbers are peculiar
only to site 2.
Confining bed C-i is 2 to 3 feet thick and it is composed of a bed of sandy
organic soil and a bed of medium to fine quartz sand. Aquifer A-1 ranges from 2
to 7 feet in thickness and it is a hard, sandy, limestone that locally contains
solution holes. Confining bed C-2 is about 17 feet thick beneath the center of
the dike and the thickness of the bed increases southward. The upper 3 feet is
composed of clayey sandy marl and the lower 14-feet is composed of fine to
coarse quartz sand. Aquifer A-2 is about 2 feet thick and is chiefly shell.
Confining bed C-3 is about 2 feet thick and consists of sandy green clay that
grades vertically into the shell in aquifers A-2 and A-3. Aquifer A-2 and
confining bed C-3 dip southward from the lake toward the agricultural area. On
the other hand aquifer A-3 is a wedge-shaped bed of shell that appeaft to
increase in thickness northward beneath the lake. Aquifer A-3 is about 10 feet
thick beneath the center of the dike and the shell is similar to that in aquifer
A-2. The upper part of aquifer A-3 contains clay and the lower part contains
sandy limestone. Confining bed C-4 is about 2 feet thick and it is composed
chiefly of fine to coarse quartz sand. Aquifer A-4 is more than 4 feet thick and
it is composed of sandy limestone.
Some seepage occurs through each bed that underlies the dike but seepage
is greatest through aquifer A-1 which has been breached by borrow canals.
Aquifers A-2, A-3, and A-4 are permeable but they are overlain by at least 10
feet of "tight" sand which retards the movement of water from the Navigation
Canal into the aquifers, therefore, seepage through aquifers A-2, A-3, and A-4 is
considered to be a relatively unimportant factor in the analysis. Silt deposits that
line the bottom and sides of the borrow canals at site 2 are also considered to be
relatively unimportant factors in determining seepage because the data indicate
that the loss in head across the deposits is relatively small. The principal recharge
boundary for the upper 30 feet of strata-that underlies the dike is the Navigation
Canal and the principal discharge boundary is the network of drainage canals
located one-quarter mile south of the dike in the agricultural area. The recharge
and discharge boundaries for the deeper strata are undermined.


WATER MOVEMENT AND FLUCTUATIONS

The principal direction of seepage at site 2 is southward from the lake
toward the drainage works in the agricultural area. Short reversals occur seasonally,
however, when the stage of the lake is routinely lowered by the Corps of
Engineers prior to the rainy season, or when heavy rains cause water levels in the
agricultural area to abruptly rise above, the lake level during the wet season.
Hydraulic profiles for January 14, 1965, June 3, 1965, and October 12, 1965
were constructed to show the direction of flow and the distribution of






REPORT OF INVESTIGATION NO. 58


equipotential lines (water levels) and isochlors for selected high and low stages of
the lake (fig. 19).
On January 14, 1965, a period of high water levels, the stage of Lake
Okeechobee at site 2 was 14.29 feet and the stage of the L-D2 Canal was 13.53
feet. Seepage through aquifers A-1 and A-2, and through confining bed C-2, was
southward from the lake toward the agricultural area. The low chloride content
and inferred steep hydraulic gradients in aquifers A-1 and A-2, and in confining
bed C-2, suggest that most of the seepage occurred there. The high chloride
content and the inferred low hydraulic gradient in aquifer A-3 (and perhaps A-4)
suggest that it conveys insignificant amounts of seepage. Water levels in bed A-3
were lower than those in bed A-2 indicating that bed C-3 retards the vertical
movement of water between overlying and underlying beds.

On June 3, 1965, a period of low water levels, the stage of the lake was
12.44 feet and the stage of the L-D2 Canal was 11.94 feet. The equipotential
lines show that seepage through aquifers A-1 and A-2, and confining bed C-2,
was southward from the Navigation Canal to the L-D2 Canal and to the
agricultural area. Hydraulic gradients in aquifer A-3 (and perhaps A-4) was low
therefore water movement there was probably insignificant. The slight lakeward
shift in chloride content in aquifer A-3 suggest that water movement there was
northward.

On October 12, 1965, a period of high water levels, the stage of the lake
was 14.54 feet and the stage of the L-D2 Canal was 14.20 feet. The data were
collected during a period of slightly unsteady water-level conditions which were
caused by locally occurring rains and strong winds. Water movement in aquifers
A-1 and A-2 and confining bed C-2, was southward from the lake toward the
agricultural area. The equipotential lines in aquifer A-1 infer a low hydraulic
gradient from the lake toward the agricultural area. The equipotential lines in
bed C-2 suggests that the permeability of bed C-2 is lower than bed A-1. The
curvature of the lines suggests that some water moved downward through bed
C-2 from the Navigation Canal and the L-D2 Canal and some water moved
upward through bed C-2 from aquifer A-2. A lakeward shift in chloride content
and hydraulic gradient in aquifer A-3 suggest that water movement there was
northward from the agricultural area toward the lake.

Figure 20 is a graph comparing the daily mean stage of the lake with the
daily highest water level in well 7 which taps aquifer A-i and is located on the
landward berm of the Hoover Dike (see location on figure 18). The water level in
well 7 is about the same as that in the L-D2 Canal. During 1964-65, the lake
level was generally higher than the water level in well 7 except during April
through June 1964, June through August 1965, and September 1965, when
heavy rains caused local water levels south of the dike to rise higher and faster
than the level of the lake.






BUREAU OF GEOLOGY


16

15

14

13


_j
-t
I.->
Ltu t


bi=.
&-4

ta 1

to

<
bJ<
tu
l u
4E


C z
If -


2.83 5.96 5.07 4.53 3.72



I III L I I 1I 11-..1 1 1 .


3.74



, Ii


0.37


0.92


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



1965




^---------------------------- --



L 67 5.33 2.65 2.92 1.27 12.77 5.76 4.28 6.47 8.07 8.25 1.15


CLEWISTON US ENG


.fi.. I I


J F M A M


J J A S 0


Figure 20. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in wel 7 at site 2; and daily and monthly
rainfall at Cewiston; 1964-65.


Generally the water level in well 7 rose in response to local rainfall and to
corresponding fluctuations of the lake. However, when the stage of the lake was
below 13.5 feet, fluctuations of the water level in well 7 were chiefly caused by
local rainfall. Short-term fluctuations of the lake level had relatively little affect
on the water level in the well, which suggested that the hydraulic connection
(the permeability of the aquifer) between well 7 and the lake is poor. The water
level in well 7 appears to be only slightly affected by drainage because the
drainage works (network of canals) are relatively far from the well and the
hydraulic connection is relatively poor. The water-level recession during April
and May 1965 was caused by the routine lowering of regional water levels by the
Corps of Engineers prior to the wet season.


S2.11 2.46 L21 5.48
3 CLEWISTON US ENG
2 1


0


!ie
14
-ju

U>

I a a, 14
itu


S02
64



z
4Z


0 6
TE5





0


-- DAILY MEAN LAKE STAGE 1964
- DAILY HIGH GROUND WATER STAGE AT WELL 7
LAND SURFACE DATUM AT WELL
14.11 FEET. MEAN SEA LEVEL -

I___t I___1---I---I---I---I--- ---- ---- ---







REPORT OF INVESTIGATION NO. 58 51



Figures 21 through 23 are graphs comparing water levels, chloride content,

and water temperature in wells that tap selected aquifers and confining beds


M J J A S ON D:J FMAM J J
1964 1965

EXPLANATION


- LAKE
L-D2 CANAL
---WELL 4


--.- WELL 7
WELL 10


Figure 21. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-I at site 2 with data for
the lake and the L-D2 Canal, 1964-65.


_j
-J
W
W
-J


-W
WJ C/)


4>
<
I-
c( 2
to

w
W
3o
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200
UJ
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,_j
W cr
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-100
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o^ ,oo


our
-J
_j
_j


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urZ
DW



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-


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I I





































































1964 1965


EXPLANATION


----LAKE
L-D2 CANAL


-- WELL 3
-*.- WELL 8


Figure 22. Graphs comparing water levels, chloride content, and water
temperature in wells that tap confining bed C-2 at site 2 with
data for the lake and the L-D2 Canal, 1964-65.


BUREAU OF GEOLOGY


-1
ta

-J



tli

ui







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u-









oul





-iS

-



I-
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W
ia:






REPORT OF INVESTIGATION NO. 58


J
w I










60 0 I I I- I-- 1 1 1 1 1 -- 1 1 II-- - -I 1 | l l-I



,.-.. i\ !
W 141

















I400- -
> 4















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00 I
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1964 1965
EXPLANATION
LAKE WELL 2
30-




















-- L-D2 CANAL -.-- WELL II
--WELL I
Figure 23. Graphs comparing water levels, chloride content and water
temperature in Wells that tap aquifer A-3 at site 2 with data for
the lake and the L-D2 Canal, 1964-65.
EXLAATO
-LK_-- WL
--ELLDWAA ELI
anowte
teprtr0n el2htta0qie0-3a ie2wihdt o

10- thlkeadteLDCaa,1665





BUREAU OF GEOLOGY


with data for the lake and the L-D2 Canal. The lines representing well data are
coded by a number of dots. The line with the least dots represents the well
nearest to the lake.
Water levels nearest the lake in aquifer A-i are closely related to the lake
level (fig. 21). This relationship indicates that the permeability of aquifer A-1 is
about the same as the permeability of the filtercake.in the Navigation Canal. The
hydraulic gradient, which is shown by water levels-in the line of wells, indicates
that water moved southward from the lake. through the L-D2 Canal toward the
agricultural area. Chloride content in water in well 4, which is nearest the lake, is
closely related to that of the lake. The lag in time between peak chloride content
in the lake and peak chloride content in the L-D2 Canal suggest that seepage
through the aquifer occurs at a slow rate. For example, the peak chloride -
concentration in the lake water occurred in April 1965 while the peak chloride
concentration in the L-D2 Canal occurred about 2 months later. Chloride
content in the landward wells and the L-D2 Canal was lower than that in the
lake, suggesting that some dilution by local recharge (rainfall) occurs there. The
temperature of the water in aquifer A-1, in the lake, and in the L-D2 Canal varies
seasonally, and the range in temperature of ground water is less than that of the
surface water but the data suggest that there is a general relation between water
movement and temperature in the lake and in aquifer A-1.
Water levels in confining bed C-2 near the lake are also closely related to
the water level in the lake (fig. 22). The similarity between the graphs in figures
21 and 22 suggest that the permeabilities of aquifer A-1 and confining bed C-2
are probably similar.
Water levels in aquifer A-3 are closely related to the water level in the
L-D2 Canal (fig. 23). The hydraulic gradient, which is inferred from the
differences between the water levels in the wells, is low, therefore the rate of
water movement in aquifer A-3 is probably slow even if the permeability of the
material is relatively high. Chloride content is highest in the water in wells which
are the deepest and farthest from the lake suggesting that seepage through A-3 is
relatively insignificant. The decrease in the chloride content in well 2 during
1964 and 1965 was probably caused by the movement of fresh water into the
aquifer from the Navigation Canal after well 2 and other nearby wells in aquifer
A-3 were pumped during sampling. The high chloride content and occasional
reverse gradient in aquifer A-3 suggest that aquifer A-3 is unimportant in the
analysis of seepage from the lake. The temperature of the water in aquifer A-3
fluctuates through a relatively narrow range and the data suggest that there is
slight relationship between water movement and temperature in aquifer A-3.

QUANTITATIVE STUDIES

Aquifer tests were performed at site 2 to determine the transmissivity (T)
and/or the hydraulic conductivity (Kf) of the beds which are the chief conveyors
of seepage from the lake.






REPORT OF INVESTIGATION NO. 58 55


A pumping test was conducted on well 2 which taps aquifer A-3. The well
was pumped for 74 minutes.at a rate of 75 gpm and water level fluctuations
were recorded in wells 1 and 11, and in the pumped well. Data from the test
indicated that recharge suppressed the drawdown in the observation wells early
in the test, therefore, it was not possible to accurately determine the
transmissivity of aquifer A-3. A few early data, however, suggested that the T of
aquifer A-3 does not exceed 70,000 gpd/ft, but the transmissivity obtained by
the slug tests was considered to be in the correct order of magnitude for aquifer
A-3. Slug tests were performed in wells 1 through 4, 7, 10, and 11 in order to
determine the magnitude of the hydraulic conductivities of various beds beneath
the dike. The results of the test are shown in table 3.

TABLE 3. RESULTS OF SLUG TESTS AT SITE 2.
Thickness1 K T
Bed (feet) (gpd/ft2) (gpd/ft)
Dike Fill 1 1002 1002
C-1 2 1002 2002
A-1 8 384 3,040
C-2 17 50 850
A-2 2 2,0002 4,0002
C-3 2 (1 (1
A-3 10 1,340 13,400

Total 42 21,590



Measured below center of dike
2Estimated


No data were obtained in confining bed C-3 and in aquifer A-4, but the seepage
there is considered to be a minor factor in the total analysis. The total
transmissivity of the 42-foot section beneath the center of the dike is about
22,000 gpd/ft. However, the distribution of hydraulic gradients in the various
beds is not uniform, therefore seepage should be computed for each bed.


SEEPAGE

Seepage from the lake at site 2 can be estimated best by determining the
flow through the 42 feet of saturated material down to confining bed C-4
underlying the dike rather than the flow through the filtercake in the Navigation
Canal. The flow through the materials for a given period can be determined from






BUREAU OF GEOLOGY


the transmissivities of the individual beds and the hydraulic gradients within the
beds. If the flow through the materials is steady state and the hydraulic gradients
in the aquifer are directly related to the hydraulic gradient across the dike, that
is, between the Navigation Canal and the L-D2 Canal, then the seepage through
the materials can be related to the long-term head across the dike. A comparison
of water levels in wells at various depths in the materials suggest that a direct
relationship between the hydraulic gradients does in fact exist. Therefore, the
flow, hence the seepage, beneath the dike was computed for January 14, 1965, a
period of steady-state water levels and above average lake levels (see profile A in
fig. 19) and the seepage from the lake was related to the head across the dike by
the seepage factor Se.
Seepage on January 14, 1965 is related to the transmissivities which were
presented in table 3 of the proceeding section, and to the hydraulic gradients in
the hydraulic profile in figure 19. The seepage through the upper 28 feet of the
materials was computed using equation 1, where T is the sum of the
transmissivities of the dike fill (saturated part), confining bed C-1, aquifer A-l,
and confining bed C-2; and I was the hydraulic gradient in aquifer A-1.

Q = TIL
= 4,190 gpd/ft x 0.00292 x 1 ft.
= 12.2 gpd per foot of width of aquifer

Seepage through 2-foot thick aquifer A-2 (fig. 19) was computed using
equation 1 where T is the transmissivity of aquifer A-2 and I was the hydraulic
gradient in aquifer A-2.

Q= TIL
= 4,000 gpd/ft x 0.0014 x 1 ft.
= 4.6 gpd per foot of width of aquifer

Seepage through 2-foot thick bed C-3 was very low and was therefore omitted in
the analysis. Seepage through the 12-foot thick aquifer A-3 was computed using
equation 1 where T is the transmissivity of aquifer A-3 and I was the hydraulic
gradient in aquifer A-3.

Q= TIL
= 13,400 gpd/ft x 0.00014 x 1 ft.
= 1.9 gpd per foot of width of aquifer

Seepage through the basal materials shown in figure 19, confining bed C-4
and aquifer A-4, was considered an insignificant factor in the analysis. Thus, the
seepage from the lake through the saturated material (42 ft deep) is equal to the
sum of the computed seepages.






-REPORT OF INVESTIGATION NO. 58


Q1 = 12.2 gpd +4.6 gpd + 1.9 gpd
= 18.7 gpd per foot of width of aquifer

However, the geologic section prepared by the Corps of Engineers (1961, plate
16) indicates that aquifer A-1, which is the chief source of seepage at site 2, is
discontinuous along the dike, therefore the seepage at site 2 is probably higher
than the average value along the section of dike assigned to site 2. However, the
seepage at site 2 is believed to be within the correct order of magnitude and is
therefore assumed to be representative of that along 8% miles of dike.
On the basis of the steady-state seepage from the lake on January 14,
1965, the seepage factor (Se) at site 2 was determined using equation 10 where
Q1 is the January 14 seepage through a one-foot wide segment of the aquifer
materials L is 1/5,280 mile, h was the stage of the lake, and hi was the stage of
the L-D2 Canal.

Q1
e L(hI -hc)

18.7 gpd/ft x 5280 ft
1 mi (14.29 ft 13.53 ft)

= 129,900 gpd/mi/ft, or about 0.2 cfs/mi/ft.

Thus the seepage factor (Se) at site 2 is about 0.2 cfs/mi/ft, which includes the
retarding effect of the filtercake in the Navigation Canal. However, the effect of
the filtercake at site 2, though small compared to that at site 1, will probably
cause a further reduction in seepage as the filtercake continues to form and the
lake is raised.
A comparison of water-level measurements in the lake with those in the
L-D2 Canal during 1964-65 suggested that the rate of seepage varied with the
stage of the, lake and stage of the L-D2 Canal. Under normal conditions, the head
across the dike was about 0.5 foot when the stage of the lake was at or below 14
feet, and the head was about 0.75 foot when the stage of the lake was about 14
feet.
When the stage of the lake was below 14 feet, the stage of the LID2 Canal
was greatly affected by local rainfall which ran off the dike and U.S. Highway 27
and accumulated in the canal. However, during the longer dry periods, the
steady seepage from the lake caused a constant head relationship (about 0.5
foot) to exist between the lake and the canal. Therefore the maximum seepage
rate that might be expected when the average stage of the lake is 14 feet would
be about (0.2 cfs/mi/ft x 0.5 ft) 0.1 cfs per mile.
When the stage of the lake is between 14 and 15 feet, the water level in the
L-D2 Canal rises above its banks, but overland flow from the canal is prevented





BUREAU OF GEOLOGY


by U.S. Highway 27 which parallels the southern side of the canal and by fill at
the terminuses of the canal. If the relationship between the lake and the L-D2
Canal remains the same for higher stages of the lake and no changes occur in
drainage, then the average stage of the L-D2 Canal would be about 15.75 feet if
the average stage of the lake is raised to 16.5 feet, and seepage from the lake
would be about (0.2 cfs/mi/ft x 0.75 ft) 0.15 cfs per mile. However, if the L.D2
Canal were connected to a drain and controlled at a constant stage of 11.5 feet
then the seepage from the lake beneath the dike would be about 0.5 cfs/mi when
the average stage of the lake was 14 feet and about 1.0 cfs/mi when the average
stage was 16.5 feet.
Thus seepage from the lake at site 2 should increase about 0.05 cfs per
mile, if the average stage of the lake is raised from 14 to 16.5 feet, the L-D2
Canal remains isolated from the drainage canals, and the prevailing drainage
conditions south of the dike do not change. The seepage beneath the 8%-mile
segment of dike represented by site 2 therefore would increase from about 0.8
cfs to about 13 cfs if the average stage of the lake were raised from 14 to 16.5
feet.

SITE 3

DESCRIPTION

Site 3, shown in figure 24, is in Palm Beach County on the southern shore
of Lake Okeechobee about 0.6 mile east of Lake Harbor.
The site consists of data-collection stations along a line about 860 feet long
which was constructed normal to the Hoover Dike, as shown in figure 25. The
stations include 11 test wells of which 6 were used to obtain data on
ground-water levels, and two observation points which were used to obtain data
on water levels in the lake and in the landside toe ditch.
North of the Hoover Dike is the Navigation Canal which was excavated in
the early thirties for borrow to construct the dike. In 1964, the north side of the
Navigation Canal was deepened for borrow which was used to raise the dike to
its present height and for borrow which was used in constructing the roadbed for
U.S. Highway 27. South of the dike is a toe ditch which was excavated in 1965
by the South Shore Drainage District to intercept seepage from the lake and to
route excess water from the agricultural area south of the highway westward
into the Miami Canal where it is pumped into the lake by the C&SFFCD.

Natural land surface at the site ranges from 13 to 14 feet above msl and is
underlain by 6 to 8 feet of soft black organic soil. Beneath the soil are beds of
clay, limestone and sand which grade vertically and laterally into each other.
Generally the beds of shell and limestone are permeable and comprise aquifers;
and beds of sand, clay, and organic soil are less premeable and comprise






REPORT OF INVESTIGATION NO. 58


EXPLANATION
PUMP STATION
PUMP
O I MILES


Figure 24. Map showing location of site 3 near Lake Harbor.


confining beds. Seepage is greatest through the beds of limestone and shell which
range from 4 feet above to 13 feet below msl in the Caloosahatchee Marl.

AQUIFERS AND CONFINING BEDS

The aquifers, confining beds and depths of observation wells along line
C-C' at site 3 are shown on profile A in figure 26. The aquifers and confining
beds are numbered consecutively with increasing depth from land surface and
the numbers are peculiar only to site 3.
Confining bed C-1 ranges from 6 to 8 feet in thickness and consists of
relatively impermeable organic soil. Confining bed C-2 is about 3 feet thick and
consists of relatively impermeable beds of soft shelly marl and hard fresh-water
limestone. Aquifer A-1 ranges from 14 to 17 feet in thickness and consists of
soft to hard, permeable beds of shell and limestone that locally contain zones of






BUREAU OF GEOLOGY


~o4Tg \r
046 -4

=I0=4= \$ s.s ---
z o ===

_V C C'
-200 0 200 400 600
RANGE,FEET
PLAN


RANGE,FEET
PROFILE
(STATION 480 + 95)


EXPLANATION
WELL
OBSERVATION POINT
RIGHT-OF-WAY LINE
ROAD
LINE OF PROFILE








FILL fine quartz sand, shell,
and limestone fragments.
SOIL organic black; and some
sand.
SILT organic black, sandy.
CLAY brown to gray, with many
Helisoma sp.; grades into
hard shelly limestone.
LIIESTONE tan to white, hard to
soft, with many Rangia sp.
SAND quartz, fine, with many
Rangia sp. and Helisoma sp.
SHELL gray to white, soft to
hard, with Macoma sp.
Cardium sp. and Pecten sp.
LIMESTONE gray to tan, hard,
porous shelly.
SAND quartz, fine.
SAND quartz, medium to fine,
with some shell.


Figure 25. Plan and profile along line C-C' at site 3.




sand. Confining bed C-3 is at least 10 feet thick and consists of fine sand which
is low in permeability. Most of the seepage occurs through aquifer A-1, although
some seepage occurs through each bed.

The silt deposits, or the filtercake, that lined walls of the Navigation Canal
were partly removed from the north side of the canal when it was deepened for
borrow in 1964. The removal of these deposits probably caused seepage to
increase; however, the slow redeposition of the silt should cause a reduction in
future seepage.








JANUARY 14, 1965


NORTH


SOUTH


-200 0 200 400 600 -200 0 200 400 600
RANGE, FEET
EXPLANATION
4== DIRECTION OF FLOW


CONFINING BED DISCUSSED
IN TEXT BY NUMBER
AQUIFER DISCUSSED IN
TEXT BY NUMBER


.,- ISOCHLOR VALUE IS
MILLIGRAMS PER LITER
I WELL NUMBER AND
UNCASED PORTION


EQUIPOTENTIAL LINE,VALUE IS 0 FILL
FEET ABOVE MEAN SEA LEVEL


Figure 26. Selected hydraulic profiles along line C-C' showing aquifers, confining beds, and depths of observation wells at site 3.


E@ DIKE


JUNE 3,1965


MAY 18,1966







BUREAU OF GEOLOGY


WATER MOVEMENT AND FLUCTUATIONS

The principal direction of water movement at site 3 is southward from the
lake to the agricultural area. Hydraulic profiles A through C in figure 26 were
constructed to show the distribution of equipotentials and isochlors, and the
principal direction of water movement on January 14, 1965, June 3, 1965 and
May 18, 1966, respectively.
On January 14, 1965, a time of high water levels, the stage of the
Navigation Canal was 14.37 feet and the stage of the water table at the southern
toe of the dike was 12.06 feet. Seepage was chiefly southward through aquifer
A-I toward the drainage canals in the agricultural area. (see profile A in fig. 26).
The chloride content of the water in aquifer A-1 was low near the lake and
relatively high in the confining beds, a condition that indicates water movement
is greater through aquifer A-1.
During February 1965, a drainage ditch was excavated into bed C-2 along
the toe of the dike from a culvert, which underlies U.S. Highway 27 near site 3,
to the Miami Canal; and another drainage ditch was excavated from the south
side of the culvert southward into the agricultural area and westward along the
south side of the highway (see profile B in fig. 26). A pump was installed at the
west end of the dike toe ditch to pump excess water from the agricultural area
south of the highway into the Miami Canal near HGS-3 at Lake Harbor.
On June 3, 1965, a time of low water levels, the stage of the Navigation
Canal was 12.42 feet and the pumping level in the toe ditch was 8.88 feet.
Seepage was southward through aquifer A-1 from the lake toward the
agricultural area, but most of the seepage was upward into the toe ditch (see
profile B in fig. 26). Water from the agricultural area and seepage was flowing
westward in the ditch to the pump which was operating at the west end of the
toe ditch. The drawdown in the ditch caused water levels in wells at site 3 to
decline, which indicated that the hydraulic gradient and seepage from the lake
had increased. However, the high chloride content of the ditch water (380 mg/1)
indicated that only a small part of the water pumped from the ditch could have
originated as seepage from the lake because the chloride content of the lake
water was only 70 mg/1.
During December 1965 the toe ditch was deepened so that the bottom of
the ditch penetrated the upper part of aquifer A-1. On May 18, 1966, a seepage
test was conducted at site 3 and the water-level data shown in profile C, figure
26, was related to the measured seepage in the toe ditch. The pumping level in
the ditch was 7.44 feet (msl) and the stage of the lake was 13.75 feet. The
closely spaced equipotential lines beneath the dike indicate that the principal
direction and rate of water movement was southward from the lake through
aquifer A-1 to the toe ditch. South of the highway, water movement in aquifer
A-1 was northward toward the toe ditch. However, the hydraulic gradient there






REPORT OF INVESTIGATION NO. 58


was lower than that beneath the dike indicating that some of the pickup, or
seepage, into the toe ditch came from the agricultural area. The seepage through
confining beds C-1 and C-2 was considered an insignificant factor in the test.
During 1964, water levels in the area south of the dike were chiefly
affected by dewatering operations during the construction of U.S. Highway 27,
as shown by the hydrograph of well 2 on figure 27. During February 1965, a toe
ditch was excavated along the southern toe of the dike and linked to the
drainage system in the fields on the south side of U.S. Highway 27. During the
remainder of 1965, the water level in well 2, located a few feet north of the toe
ditch, was largely affected by drainage operations of the agricultural area and the
stage never exceeded 12 feet. Prior to excavation of the toe ditch, the water level
in the aquifer at the toe of the dike probably ranged from 12.0 to 12.5 feet, or
about the same as the range in stage of the water level in well 2 during December
1964 through January 1965.
Figures 28 and 29 are graphs comparing water levels, chloride content, and
water temperatures in the lake and the toe ditch and in wells that tap aquifer
A-1 and confining beds C-1 and C-2. The lines representing well data are coded
by dots and the line with the least dots represents the well closest to the lake
while the line with the most dots represents the well farthest from the lake.
Graphs of water levels, chloride content, and temperature in wells that tap
aquifer A-1 are compared with those in the Navigation Canal and in the toe ditch
during 1964-65 in figure 28. Water levels were highest in the well nearest the
lake and lowest in the well nearest the agricultural area, thereby indicating that
seepage was at all times southward from the lake. During 1964 water levels in
the wells were lowered by dewatering operations during the construction of U.S.
Highway 27 and by the drainage operations in the agricultural area. During 1965
the drawdown in the toe ditch lowered water levels in the observation wells,
indicating that the toe ditch had intercepted some of the seepage from the
lake. A comparison of chloride content in the wells in aquifer A-1 with the
chloride content in the lake suggests that aquifer A-1 is the principal conveyor of
seepage from the lake because the concentrations are about equal. A comparison
of the chloride content in the wells with the chloride content in the toe ditch
suggests that most of the water that is pumped from the agricultural area is
derived from an inland source which is high in chloride content. A comparison
of chloride peaks in the lake and chloride peaks in the ditch (fig. 28) suggests
that variations in the quality of the lake at site 3 are partly caused by brackish
ground water which is pumped from the agricultural area through the Miami
Canal into the lake during wet periods. A comparison of the temperature data
shows that ground-water temperatures in wells 3 and 6 lag the temperature of
the lake by several months, indicating that the movement of water through the
aquifer is at best slow.
Water levels, chloride content, and temperatures in confining beds C-1 and
C-2 are compared graphically with those in the toe ditch and the lake in figure





64 BUREAU OF GEOLOGY




1964




z 13
44 34




If



DAILY MEAN LAKE STAGE
c8 -a DAILY HIGH GROUND WATER STAGE AT WELL 2
LAND SURFACE DATUM AT WELL Z
7 13.32 FEET, MEAN SEA LEVEL



S4 -2.11 246 2.83 548 I 2.63 5.96 5.07 4.53 3.72 3.74 0.37 0.98
S3 C EWISTON US ENG
2


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



> 1965




_>3- 15 UEN
4c







I-A,







S-6-wa 5.331 levels in well 2 at site 3; 4.28d daily d07 0.25 1.15monthly





rainfall at Clewiston; 1964-65.







REPORT OF INVESTIGATION NO.58


- LAKE
- TOE DITCH
-'- WELL 3


EXPLANATION


-.-- WELL 4
---WELL S


tl q Io- i

1 I I I 1' I I



J F MA M JJ A S O N J FMAM J JASONO
1964 r9s5



Figure 28. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-I at site 3 with data for
the lake and the toe ditch, 1964-65.





66 BUREAU OF GEOLOGY


29. The water level in well 5 (taps bed C-1) south of the highway is directly
affected by the drawdown in the nearby toe ditch. The drawdown in well 1
(near the lake in bed C-2), is caused indirectly by the drawdown in aquifer A-1.
A comparison of the chloride content in well 1 with the other chloride
data in figure 29 suggests that the uniformly high chloride content in well 1 is an
indication that seepage from the lake through the filtercake and confining beds
is very slow. The time lag between the peak temperature in the lake and the peak
temperature in well I also suggests that the rate of seepage through bed C-2 from
the lake is slow.
A comparison of the chloride content in wells 4 and 5 (fig. 29) with the
chloride content in wells 3, 4 and 6 (fig. 28) shows that the water in beds C-1 -
and C-2 contain slightly higher concentrations of chloride than bed A-l,
therefore the high chloride content in the surface water (in canals and ditches)
that is pumped from the agricultural area could be caused by the local flushing
of brackish ground water from beds C-1 and C-2, or by flushing of residual
brackish ground water from aquifer A-1 in an area considerably distant from the
lake.
QUANTITATIVE STUDIES
Tests were performed at site 3 to determine the transmissivities of the beds
which are the chief conveyors of seepage from the lake. A pumping test was
conducted on well 4, which taps aquifer A-1. Well 4 was pumped for 62 minutes
at a rate of 30 gpm and the water level fluctuations were measured in wells 1, 2,
and 6, and in the pumped well (4). The data indicated that recharge from the
Navigation Canal and the ditches south of the dike suppressed the drawdowns in
the observation wells early in the test. However a few early data suggested that
the T of aquifer A-1 is about 16,000 gpd/ft. No effects of pumping were
observed in the nearby shallow wells suggesting that the permeabilities of
confining beds C-1 and C-2 are low.
Slug tests conducted in the wells 1 through 7, suggested that the
transmissivity of aquifer A-1 is about 18,000 gpd/ft., and the transmissivities of
confining beds C-1 and C-2 are about 20 gpd/ft. and 200 gpd/ft respectively
(table 4).

TABLE 4 RESULTS OF SLUG TESTS TEST AT SITE 3.

Thickness Kf T
Bed (feet) (gpd/ft2) (gpd/ft)

C-i 7 3 21
C-2 2.5 82 206


15 1,200


18,000








REPORT OF INVESTIGATION NO. 58


V EXPLANATION

1964

,I I I I I I I I I I I I I I I I I -- LAKE I C
I I I I I I _I II ~ TOE DITCH
1965
---WELL I (BED C-2}
----WELL 5 (BED C-1)































J FMA MJ A SON J FM AM J J ASO N




Figure 29. Graphs comparing water levels, chloride content, and water
temperature in wells that tap confining beds C-1 and C-2 at site
3 with data for the lake and the toe ditch, 1964-65.


Z 90
5 SO
IIW
s- o0



a --


I J' r+k





BUREAU OF GEOLOGY


A seepage test was conducted on May 18, 1966 at site 3 in a 1,000-foot
reach of the toe ditch which parallels the dike (see profile C in fig. 26). Pumping
from the ditch was of sufficient duration that water levels approached steady
state. About 0.2 cfs of seepage was measured in the 1,000-foot reach. The shape
of hydraulic profile at site 3 during the seepage test indicates that the ditch was
receiving seepage from both the lake and the agricultural area. The hydraulic
gradients indicated that most of the seepage was from the lake. The
transmissivity of aquifer A-1 was estimated using equation 9, where Qc was the
pickup in the 1,000-foot reach (0.2 cfs or 129,600 gpd), ASc was an insignificant
value, L was 1,000 ft, I was the hydraulic gradient from the lake (0.0073), and
la was the hydraulic gradient from the agricultural area (0.000154)
Qc ASc 129,600 gpd
L (Ii + Ia) 1,000 ft (.007454)

= 17,500 gpd/ft.

Thus results of the tests indicate that the transmissivity of aquifer A-1 is
about 17,500 gpd/ft and that permeabilities of confining beds C-I and C-2 are
low.
SEEPAGE

Seepage from the lake at site 3 can be estimated best by using the
transmissivity of the water-bearing strata that underly the dike and the average
hydraulic gradients therein. On the other hand seepage from the lake can be
related to the head across the dike if the head in the aquifer is directly related to
the head across the dike. Seepage through a 1,000-foot long section of aquifer
A-I on May 18, 1966 was 0.2 cfs when the stage of the lake was 13.75 ft and the
stage of the toe ditch was 7.44 ft. The transmissivity and drainage conditions
were considered to be uniform along the 1,000-foot section of dike which was
represented by the steady-state water levels at site 3. The seepage was expressed
in terms of the seepage factor (Se), which was determined by using equation 10,
where QI is 0.2 cfs, L is 0.189 mile, hi is 13.75 ft., and hc is 7.44 ft.

se -
L (h1 hc)

0.2 cfs
0.189 mi (13.75 ft 7.44 ft)

= 0.168 cfs/mi/ft.

Thus the seepage factor at site 3 is about 0.2 cfs per mile per foot of head
between the water level in the lake and the water level in the toe ditch. The





REPORT OF INVESTIGATION NO. 58


seepage factor includes the head losses which might be attributed to the
filtercake in the Navigation Canal; however, seepage from the lake will decrease
as the filtercake, which was partly removed during construction activities in
1964, is redeposited.
Estimation of the increase in seepage that would result from raising the
average stage of the lake from 14 feet to 16.5 feet requires a knowledge of the
long-term relationships between the lake level and the water level in aquifer A-1
at the toe of the dike. Because those data are lacking, it must be assumed that
some of the water-level data collected at site 3 during 1964 are representative of
the long-term seepage conditions prior to changes in drainage and that some of
the water-level data collected during 1965-66 are representative of the
conditions which might be expected if a constant head drainage ditch, such as
the ditch at site 3, were excavated into aquifer A-1 along the landside toe of the
entire 8%-mile section of dike represented by site 3.
Prior to the excavation of the toe ditch at site 3 the average water level in
aquifer A-1 at the foot of the dike was probably at a stage of about 12.5 feet;
therefore, when the average lake stage was 14 feet, the average rate of seepage
was about 0.3 cfs per mile. If no changes in drainage occurred and the average
stage of the lake was raised to 16.5 feet, then the seepage would have increased
from 0.3 to about 0.8 cfs per mile.
During 1965-66, the water level in the toe ditch at site 3 was controlled by
pumping at a stage of about 9 feet; therefore, the average rate of seepage was
about 1.0 cfs per mile when the average lake stage is 14 feet. If the average stage
of the lake is raised to 16.5 feet then the seepage would increase from 1.0 to
about 1.5 cfs per mile.
Due to the excavation of the toe ditch, the seepage at site 3 is not
representative of the seepage along the assigned 8%-mile length of dike. The
seepage along the 8% miles of dike is considered to be related to the conditions
at site 3 prior to excavation of the ditch, therefore, seepage from the lake along
the 8 miles can be expected to increase from about 2.6 to 6.8 cfs as a result of
raising the average lake stage from 14 to 16.5 feet. However, if a toe ditch
similar to that at site 3 is excavated along the 8-miles of dike and the water level
therein is controlled at a stage of 9 feet, then seepage from the lake will increase
from 8.0 to 12.8 cfs if the average stage of the lake is raised from 14 to 16.5
feet.

SITE 4

DESCRIPTION

Site 4, as shown in figure 30, is in Palm Beach County on the southeastern
shore of Lake Okeechobee about, 3 miles northwest of Belle Glade. The site





BUREAU OF GEOLOGY


F BELLE GLADE XAT
EXPLANATION


PUMP STATION
PUMP
---- CITY BOUNDARY
0 I Z MILES


Figure 30. Map showing location of site 4 near Belle Glade.



consists of data-collection stations along a line about 1,400 feet long, as shown
in figure 31, which was constructed normal to the Hoover Dike. The stations
include 10 test wells, of which 6 were used to obtain data on ground-water
levels, and two observation points (OP's) which were used to obtain water-level
data in the lake and in the system of drainage canals in the nearby agricultural
area. North of the dike is the Navigation Canal which was excavated in the
thirties for borrow to construct the Hoover Dike. In 1963, borrow was taken
from the west side of the Navigation Canal to raise the dike to its present height,
as shown on the figure 31. South of the dike is a shallow ditch about 80 feet






REPORT OF INVESTIGATION NO. 58 71


9r \ EXPLANATION
\ 0 1
ZU.9 fl I I 01 tl
090 \ N e a a OBSMRVATION POINT
'D -\ -I- 11GHT-W-WAT LUI
S \ \ i D-D LmaI or raOn
-200 0 200 400 600
RANGE, FEET
D PLAN D
40
HOOVER DIKE
30 FILL fine quartz sand, shell,
LAKE OKEECHOBEE and limestone fragments.
SSILT organic, black, sandy.
2W NAVIGATION CANAL 4 LI=MSTONE gray, hard to soft,
shelly; grades into marl.
o 1 NARL white to gray, sticky.
o LDIBSTONE brown, hard, dense.
S BULL white, hard to soft;
chiefly Helisoma sp.,
SEA -= Fontigens ap., Chione sp.,
LEVEL and Astarte sp.; and some
sand.
.... ^^ ^ LI~DSTONI gray, hard, porous,
ishelly.
I SAND quartz, fine to coarse,
with some shell.
*LI aLDUSTOHK gray, hard, sandy,
-200 0 200 400 porous.
RANGE,FEET
PROFILE
(STATION 980)




Figure 31. Plan and profile along line D-D' at site 4.

wide, which parallels the toe of the dike. East of the ditch are fields which are
drained by a system of north-south lateral ditches that are about 6 feet deep.
The lateral ditches are spaced about 0.1 mile apart and they are connected to
larger east-west canals. Water in the east-west canals can be pumped into a main
north-south canal at State Road 715. Water levels in the agricultural area are
regulated by the South Florida Conservancy Drainage District.

Natural land surface ranges from 13 to 14 feet above msl and is underlain
by about 8 feet of organic soil (fig. 31). Beneath the soil are beds of shell, marl,
limestone, and sand, which grade laterally and vertically into each other.
Generally beds of limestone and shell comprise aquifers, and beds of organic soil,
marl, clay and fine sand comprise confining beds. Seepage is probably greatest
through permeable beds of limestone and shell that range between 2 and 6 feet
above msl in the Fort Thompson Formation and through a permeable bed of
limestone that ranges between 2 and 12 feet below msl in the Caloosahatchee
Marl.





72 BUREAU OR GEOLOGY


AQUIFERS AND CONFINING BEDS

Aquifers, confining beds, and the depths of observation wells along line
D-D' are shown on profile A in figure 32. The aquifers and confining beds are
numbered consecutively with increasing depth from land surface and the
numbers are peculiar only to site 4.

w> -0





--0

-o ro
g> wz

0 0 8 Z Wr
0 - 00
-- FZ-








Z
I__.' -_ I >


W < l .. -I
0 (-- -l


< W- _W-
-M W

w 0 Z- ir <
5 ^ Z, 5< f5W


0 0 o O -


Figure 32. Selected hydraulic profiles along line D-D' showing aquifers,
confining beds and depths of observation wells at site 4.






REPORT OF INVESTIGATION NO. 58


Confining bed C-1 ranges from 8 to 10 feet thick and is composed of
relatively impermeable, silty, organic soil. Bed C-1 retards the movement of
water between the surface and the underlying beds, however its confining ability
is locally ineffective where the bed is penetrated by canals and drainage ditches.
Aquifer A-1 ranges from 0 to 4 feet thick and is composed of porous, permeable,
gray limestone which grades laterally and vertically into clayey marl. The
permeability of bed A-1 is locally high in solution zones. Confining bed C-2
ranges from 5 to 6 feet thick and is composed of shelly marl and limestone. Bed
C-2 is relatively impermeable and confines water in the underlying aquifer.
Aquifer A-2 ranges from 7 to 8 feet thick and is chiefly composed of porous
limestone and shell. Confining bed C-3 is more than 6 feet thick and composed
of fine to coarse sand with some shell and local beds of sandy limestone. The
permeability of bed C-3 is assumed to be low because of the fine sand content.
Some seepage occurs through each bed but aquifer A-2 is the chief
conveyor of seepage from the lake. Seepage .is greatest through aquifer A-2
because it is highly permeable and it is exposed to direct infiltration from the
lake in the new borrow on the west side of the Navigation Canal. Seepage
through aquifer A-1 is retarded by the silt deposit, or filtercake, which lines the
eastern wall of the Navigation Canal. Seepage through aquifer A-2 is expected to
slowly decrease as the filtercake is redeposited on the walls of the new borrow.

WATER MOVEMENT AND FLUCTUATIONS

The principal direction of water movement at site 4 is eastward from the
lake into the agricultural area. Short-termed reversals occur when the level of the
lake is routinely lowered by the Corps of Engineers to create storage space
prior to the annual rainy season. Hydraulic profiles A and B in figure 32 were
constructed from water level data for June 4, 1965 and October 11, 1965,
respectively, to show the direction of seepage and the distribution of
equipotential lines and isochlors for low and high stages of the lake.
On June 4, 1965, a time of low water levels, the stage of the lake was
12.46 feet above msl and the stage of a ditch east of site 4 in the nearby drainage
system in the agricultural area (shown in fig. 30) was about 10.4 feet. Water
moved eastward from the lake through aquifers A-1 and A-2 toward the drainage
system. The water levels in aquifer A-1 had been lowered by the drainage
operations in the nearby fields however the water levels in aquifer A-2 had
apparently been unaffected. The close spacing of the equipotential lines in beds
C-1 and A-1 near the Navigation Canal indicates a relatively large loss in head
occurred across the filtercake that lines the navigation Canal. Water movement in
aquifer A-2 was chiefly eastward toward a distant point of discharge, probably
the deep canals near State Road 715. The nearly horizontal equipotential lines in
bed C-2 suggest that the bed confines the water in aquifer A-2 and that some
water seeps upward from bed A-2 into bed A-1.





BUREAU OF GEOLOGY


The 50 mg/1 chloride content in aquifer A-1 suggest that part of the water
in the aquifer A-i was diluted by local rainfall because the chloride content in
the lake and in aquifer A-2 was between 70 and 80 mg/1. The nearly uniform
chloride content in the lake and in aquifer A-2 indicates that the seepage from
the lake occurs chiefly through aquifer A-2. About 200 mg/1 chloride content
was found in the canal water at State Road 715, about % mile east of site 3,
suggesting that most of the surface water in the agricultural area is derived from
a source other than seepage from the lake.
On October 11, 1965, a time of high water levels, the stage of the lake was
14.45 feet and the stage of a ditch in the agricultural area near State Road 715
(shown in fig. 30) was about 8.8 feet. Water moved eastward from the Jake
through aquifers A-i and A-2 toward the agricultural area. Water levels in aquifer
A-1 had been lowered by the drainage operations in the nearby fields. However,
the water levels in aquifer A-2 were relatively unaffected by the nearby surface
drainage, a condition which indicates that most of the seepage through aquifer
A-2 moved eastward beneath the nearby ditches and canals toward a more
distant discharge point in the agricultural area. The chloride content of the canal
water near State Road 715 was about 400 gm/l, which suggest that most of the
surface drainage is related to a source other than the lake because the.lake water
contained 120 mg/1 chloride. Chloride content in the lake at site 4 is usually
highest during wet periods when excess water is pumped from the agricultural
area into the lake.
A graphical comparison of the fluctuations in the stage of the lake and the
water level in well 1, which is located east of the dike and taps aquifer A- 1, with
local rainfall shows that the water level in well 1 is chiefly influenced by local
rainfall, shown on figure 33. Water level peaks were caused by rain, and water
level troughs were caused by local drainage operations. The relationship between
drainage operations and the water-level fluctuations in well 1 indicates that the
nearby drainage ditches tap aquifer A-1. Water levels in the nearby fields are
probably controlled at a stage of 11 feet.
Water levels, chloride content and water temperature in wells that tap
aquifers A-1 and A-2, respectively, are compared with data for the lake in figures
34 and 35. The lines are coded with dots and the line with the least number of
dots represents the well nearest to the lake.
The water levels in the wells tapping aquifer A-i fluctuated between 1 and
4 feet below the stage of the lake (fig. 34). The relatively small spread between
the water levels in the wells shows that the hydraulic gradient .in the aquifer
beneath the dike was relatively low. Because of the low hydraulic gradient, the
rate of seepage from the lake in aquifer A-i is probably slow. The chloride
content in well 2, located nearest the lake, is generally less than that of the lake.







REPORT OF INVESTIGATION NO. 58 75


u16o 1 1 1-1 64
15 DAILY MEAN LAKE STAGE
-- DAILY HIGH GROUND WATER STAGE
J~2 ~LAND SURFACE DATUM AT WELL I -.,
( 14 13.33 FEET MEAN SEA LEVEL
- o 1 1 111,1 1121
13













J F M A M d J A S O N D







1 61

w 1965


W1 -
> z






















5 ().26 3.44 2.36 1.11 1.34 15.25 7 .07 16 4.53 9.16 0.32 1.38
i-Il


































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




Figure 33. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 1 at site 4; and daily and monthly
rainfall at Belle Glade; 1964-65.
rainfall at Belie Glade; 1964-65.






BUREAU OF GEOLOGY


J F M A M J J A S 0 N DIJ F M A M J J A S 0 I
1964 EXPLANATION 1965

LAKE ---WELL I
---WELL 2 ---WELL 3

Figure 34. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-I at site 4 with data for
the lake, 1964-65.


-1





aJ


i.ul
w







-
(i2
LLI



U-




tlT






I,-








LL,
^







CrZ


bJ Lii
CL
M. C
_Li











Cr
(D:







REPORT OF INVESTIGATION NO. 58


_1
-J


_w
>

W<
.J








901S
wff

-w

w
-u
4 >


I--
W
LU-


0:200


-j
aw
Q J
W0
0 100
_j

-J
-J


-W
.w
WUI
rZ
LUJ

i1
0:4
CLu
UJ U
0.
S n
I-w
0
W
a
UJ


J F M A M J J A S O N D J F M A M J J A S 0 N D
1964 EXPLANATION 1965

LAKE ----WELL 5
WELL 4 -----WELL 6

Figure 35. Graphs comparing water levels, chloride content, and water
temperature in wells that tap aquifer A-2 at site 4 with data for
the lake, 1964-65.


-.I i. i i 0\







I I I I I I I I I I i -I l I I I


I I





BUREAU OF GEOLOGY


The lower chloride content in wells 1 and 3, however, suggests that some low
chloride source, such as local rainfall on the east side of the dike, accounts for a
large part of the water in aquifer A-1 at this site. Fluctuations of water
temperature in aquifer A-i lag fluctuations of temperature in the lake, a
condition which suggests that the rate of seepage from the lake is relatively slow,
if the temperature changes in aquifer A-1 are due to seepage from the lake. Thus
the data suggest that the drainage ditches in the nearby fields tap aquifer A-l,
that the drawdown effects from pumping the ditches extends beneath the dike;
and that seepage from the lake is retarded by the filtercake in the Navigation
Canal.

The water levels in aquifer A-2 at site 4 are slightly lower than the water in
the lake (fig. 35). Generally, the water level in well 4, located nearest the lake,
fluctuated in concert with that of the lake, while the water levels in wells 5 and
6, located farthest from the lake, were only slightly affected by drainage
operations in the agricultural area. During 1964-65, the chloride content and
temperature in the wells tapping aquifer A-2 were nearly constant whereas the
chloride content and temperature of the lake fluctuate seasonally. The
temperature, chloride, and water-level data suggest that the seepage rate through
aquifer A-2 is slow, and that the aquifer probably conveys a relatively small
amount of seepage from the Navigation Canal in the lake to the drainage system
in the agricultural area. The fact that water levels in aquifer A-2 were relatively
unaffected by local drainage operations indicates that confining bed C-2 is
relatively impermeable.



QUANTITATIVE STUDIES


Aquifer tests were conducted at site 4 to determine the transmissivity
and/or the hydraulic conductivity of the water-bearing materials underlying the
dike. A pumping test was conducted in well 5 which taps aquifer A-2. Well 5 was
pumped for 95 minutes at a rate of 37 gpm while fluctuations of the water levels
in the aquifer were measured in observation wells 4 and 6. The results of the test
indicate that the transmissivity of aquifer A-2 is about 24,000 gpd/ft. Slug tests
were performed in wells 1 through 6 to determine the hydraulic conductivities
of the materials. The results of the tests were highly variable, indicating that Kf
(the hydraulic conductivity) of aquifer A-1 could range from 100 to 4,000
gpd/ft and the Kf of aquifer A-2 could range from 1,000 to 2,000 gpd/ft2. On
the basis of the lithology and the slug tests, it was concluded that the
transmissivity of aquifer A-1, (slightly more than a foot thick in places) is about
4,000 gpd/ft and the trahnmissivity of aquifer A-2 (about 8 feet thick) is about
16,000 gpd/ft (table 5).





REPORT OF INVESTIGATION NO. 58 79


TABLE 5. RESULTS OF SLUG TESTS AT SITE 4.
Maximum
Thickness Kf T
Bed (feet) (gpd/ft2) (gpd/ft)
Dike Fill
A-1 4 100- 1,000 400- 4,000
A-2 8 1,000- 2,000 8,000- 16,000


However, on the basis of the combined results of the tests, it was estimated that
the transmissivity of aquifer A-1 is 4,000 gpd/ft and that the transmissivity of
aquifer A-2 is 24,000 gpd/ft; and these values were used to compute seepage
from the lake.


SEEPAGE

Seepage from the lake at site 4 can be estimated best by determining the
flow through 25 feet of saturated material underlying the dike. The flow
through the materials for a given period can be determined if the transmissivities
of the aquifers within the materials and the hydraulic gradients are known. A
comparison of the fluctuation of water levels in wells in the agricultural area
with that of the lake shows that hydraulic connection exists, and comparison of
water levels in wells and the lake at a given time establishes the gradient.
Therefore the seepage through aquifers A-1 and A-2 was computed for June 6,
1965, a time of low water levels, and for October 11, 1965, a time of high water
levels; and the seepages were related to the hydraulic gradient between the lake
and the water level in well 1 in order to determine the seepage factor (Se) in the
same manner as shown in the previous sections pertaining to seepage at sites 1, 2,
and 3. The results of the analysis are shown in table 6.



TABLE 6. RESULTS OF SEEPAGE ANALYSIS AT SITE 4.


QA-1 QA-2 Qtotal Se
Date (cfs/mi) (cfs/mi) (Cfs/mi) (cfs/mi/ft)

6-4-65 0.01 0.24 0.25 0.12
10-11-65 0.03 0.41 0.44 0.13


The seepage factor at site 4 is about 0.1 cfs per mile per foot of head between
the lake and well 1.





BUREAU OF GEOLOGY


The geologic cross section prepared by the Corps of Engineers (1961, plate
17) indicates that there is considerable variation in the material underlying the
10-mile section of dike represented by site 4. Even so, the seepage factor at site
4 is estimated to be within the order of magnitude which would be expected
for the type of material. The seepage factor includes the present retarding effect
of the filtercake in the Navigation Canal. The seepage factor at site 4 will
probably decrease in the future as the filtercake is slowly redeposited on the
exposed portions of the aquifers in the bottom of the Navigation Canal.
Long-term water-level data in the nearby agricultural area are needed to
determine the average seepage from the lake. These data are lacking. However
water-level data for well 1 during 1964-65 (see fig. 33) suggest that the
operations in the nearby drainage district control the water levels in the nearby
fields at about a stage of 11 feet. On this basis, the average rate of seepage from
the lake at site 4 would probably be about 0.3 cfs/mi when the average lake
stage is 14 feet, and about 0.55 cfs/mi when the average lake stage is 16.5 feet.
Therefore seepage from the lake along the 10-mile section of dike represented by
site 4 should increase from 3 to 5.5 cfs if the average lake stage is raised from 14
to 16.5 feet.
SITE 5

DESCRIPTION

Site 5 is in Palm Beach County on the eastern shore of Lake Okeechobee
about 1.2 miles north of Canal Point, as shown in figure 36. The site consists of
data-collection stations along a line about 1,600 feet long which was constructed
normal to the Hoover Dike. The stations include 9 test wells, of which 6 were
used to obtain data on ground-water levels, and two observation points which
were used to obtain water level data in the lake and in the landside toe ditch,
shown in figure 37. West of the dike is the lake and the Navigation Canal which
was excavated in 1964 for borrow to raise the Hoover Dike to its present height.
The filled channel on the west side of the Navigation Canal was excavated for
borrow to construct the dike in the early thirties and was backfilled with organic
material in 1964. East of the dike is a shallow toe ditch which conveys runoff
and seepage southward to the West Palm Beach Canal at Canal Point. East of the
ditch is the Florida East Coast Railroad and a 200-foot wide sand ridge on which
U. S. Highway 441 and most of the residences and businesses are located. About
0.6 mile east of U. S. Highway 441 is a drainage canal used for flood control by
the Pelican Lake Drainage District (not shown on fig. 37).
Natural land surface ranges from 15 feet above msl at the landside toe of
the dike to 19 feet at the top of the sand ridge. The area is underlain by 7 to 8
feet of organic soil, 3 to 4 feet of marl, 23 feet of shell and hard crystalline
limestone, and at least 15 feet of fine sand (fig. 37). Generally, beds of limestone
and shed are aquifers and beds of organic soil, marl, and fine sand are confining






REPORT OF INVESTIGATION NO. 58


EXPLANATION

PUMP
-- TOE DITCH

0 I 2 MILES
I !


Figure 36. Map showing location of site 5 near Canal Point.








EXPLANATION
WILL
OBSERVATION OINTP
RIGHT-OF-WAY LINK
ROAD
LINK OF PIOFILI


40~ P'LAT4

HOOVER DIKE LAME OKEieCHooE
30-
U.& HWY 441
ed- 6 AILNOAD VGTO
DIT@N TME ISLAND
a N9W ON@W P
I OLD-90
/Z -


ICI

VIMI' 41 /I2 CjfJf
Um( fill:z::.


'AMAL


IT
RNOW PIT
:LL1)fra


FILL sand, shell, and limestone
fragments; crushed granite
in railroad bed.
O SAND quartz, fine.
* SOIL organic, black, sandy.
SILT organic, black; and sand.
KMAIL brown to white, shelly.
SHELL white to gray, soft.
2 LNBSTOHI gray, very hard to
soft, shelly, porous.
* LIM182TO gray, soft, shelly;
with layers of sand.
* S0 quarts, fine, shelly.


E-E


LE


~ i'lli/I 7/ !U/lhJ.I~ilgmniirihy
-400 -26 0 200 4M 60N wm lioo
RANGE ,FEET
PROFILE


i


&





REPORT OF INVESTIGATION NO 58


beds. The shelly limestone which underlies the dike between 12 and 20 feet
below msl in the Caloosahatchee Marl is the most permeable unit.

AQUIFERS AND CONFINING BEDS

The aquifers, confining beds, and depths of observation wells along line
E-E' at site 5 are shown on profile A in figure 38. The aquifers and confining
beds are numbered consecutively with increasing depth and the unit numbers are
peculiar only to site 5.
Confining bed C-1 has a maximum thickness of 12 feet. The upper 8 feet is
organic soil and the lower 4 feet is clayey shelly marl. The bed is about 9 feet
thick beneath the sand ridge and about 3 feet thick beneath the dike. Bed C-1 is
relatively impermeable and confines the water in the underlying aquifer. Aquifer
A-1 has a maximum thickness of 22 feet. The upper 2 feet is permeable shell and
soft permeable limestone which is underlain by a 12-foot bed of hard crystalline
limestone that locally contains stringers of sand. The lower 8 feet is soft, porous,
shelly limestone that locally contains stringers of sand.
Confining bed C-2 is at least 15 feet thick. It is chiefly composed of fine,
quartz sand and it is relatively impermeable.


WATER MOVEMENT AND FLUCTUATIONS

The principal direction of water movement at site 5 is eastward from the lake
toward the drainage canals in the agricultural area. Short term reversals occur
however when the water levels in Lake Okeechobee are routinely lowered by the
Corps of Engineers prior to the annual rainy season and water flows westward
toward Lake Okeechobee. Hydraulic profiles A and B in figure 38 were
constructed for June 4, 1965 and October 11, 1965 respectively, to show the
direction of seepage, and the distribution of equipotential lines and isochlors for
high and low stages of the lake.

On June 4, 1965, a time of low water levels, the stages of the lake and the
water level in the toe ditch were about 12.4 feet. Flow through confining bed
C-1 was chiefly westward from the sand ridge toward the toe ditch. However,
seepage into the ditch was insignificant due to the low permeability of the
confining bed. The widely spaced equipotential lines show that flow through
aquifer A-1 was eastward from the lake toward the drainage canals in the
agricultural area, and that the hydraulic gradient was low. The nearly horizontal
equipotential lines beneath the sand ridge at U. S. Highway 441 indicate the loss
in head across confining bed C-1. Flow through aquifer A-1 was eastward toward
the drainage canals in the Pelican Lake Drainage District. Seepage was induced
by pumping in the agricultural area at the time of the measurement.







OCTOBER 11,1965


ii




ii


iii





[I
~tTj
I t!7~
sIn'


E DIKE
CONFINING BED DISCUSSED
IN TEXT BY NUMBER
O AQUIFER DISCUSSED IN
TEXT BY NUMBER
] FILL
SSAND RIDGE


E EAST


1000 -400
RANGE, FEET
EXPLANATION


WEST40
r40


0 400 800 1000


_= DIRECTION OF FLOW
-14.00- EQUIPOTENTIAL LINE VALUE IS
FEET ABOVE MEAN SEA LEVEL
ISOCHLOR VALUE IS
80 MILLIGRAMS PER LITER
16 WELL NUMBER AND
UNCASED PORTION


JUNE 4,1965






REPORT OF INVESTIGATION NO. 58


On October 11, 1965, at time of high water levels, the direction of flow
through confining bed C-1 was eastward from the lake and westward from the
ground-water mound beneath the sand ridge toward the tow ditch. However, no
significant flow was observed in the toe ditch, which confirmed that bed C-1 is
relatively impermeable.
Flow through aquifer A-1 was eastward from the lake toward the drainage
system in the agricultural area. Comparison of the spacing of the equipotential
lines in the profiles indicates that the rate of flow on October 11 was more than
twice the rate during June 4; and the eastward shift of isochlors on October 11
also indicates that flow from the lake through aquifer A-1 had increased.
The daily stages of the lake and the water level in well 2, located at the toe
of the dike and tapping aquifer A-1, are compared on figure 39. The water level
in well 2 fluctuates primarily in response to changes in the level of the lake.
Short-term fluctuations in the well were caused by seiche and wind tides in the
lake and by drainage operations in the agricultural area east of the dike.
Drawdown in the well by the drainage was greatest after heavy rains in mid
October 1964, but daily drawdowns of a few hundredths of a foot were
common. The data indicate that there is a linear relationship between the stage
of the wells and the stage of the lake and that locally a good hydraulic
connection occurs between the lake and aquifer A-1.
Water levels, chloride content, and water temperatures in confining bed C-1
and aquifer A-1 are compared with data for the lake in figures 40 and 41,
respectively. The data on the graphs are coded so that the line with the least dots
represents the well nearest the lake.
Water levels in well 3 located west of the dike in bed C-1 compare
well with the stage of the lake while the water levels in wells 4 and 5 located east
of the dike do not (fig. 40). The water level in well 4 landsidee toe of dike) is
about comparable to the water level in the toe ditch which drains southward
into Palm Beach Canal. The .water level in well 5 indicates that water levels
beneath the sand ridge are oftcn higher than the lake level.
Prior to'the excavation of the toe ditch in August 1964, the area between
the dike and the sand ridge was periodically inundated following periods of
heavy rainfall. Many local residents believed that the flooding was caused by
seepage from the lake. However, hydrologic data, and on site investigation of the
flooded area have led this investigator to conclude that flooding was due chiefly
to inadequate surface drainage and to seepage.westward from the sand ridge and
not due to seepage from the lake. For example, on July 8, 1964 the water level
in the area between the toe of the dike and the railroad was 15.45 feet above msl
(more than a foot above land surface) while the stage of the lake was only 13.2
feet. Obviously, the direction of seepage must have been toward the lake and not
from the lake. Therefore the observed flooding at that time was caused by
runoff that was trapped in the small basin between the railroad and the dike.





BUREAU OF GEOLOGY


\ -I-I- I I 19 '64 1 1 l1 -1I-
DAILY MEAN LAKE STAGE
S .J DAILY HIGH GROUND WATER STAGE AT WELL 2
-75 LAND SURFACE DATUM AT WELL 2
S14 14.42 FEET MEAN SEA LEVEL





5 I
4 -3.32 2.04 0.93 3.67 2.05 13.52 9.02 8.59 5.65 6.63 0.45 4.43
3 CANAL POINT
-z
sz o IIF M AislAm ^
I







S' 220 2.04 4.50 .25 7.227.32 13.240.32 1.13

II i 1.11 II i .I i Qi

S 9714-54 20 .04 10.25 8.0 7.2 7.3
LL -_ CANAL POINT I |


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

Figure 39. Graphs showing daily stages of Lake Okeechobee and
ground-water levels in well 2 at site 5; and daily and monthly
rainfall at Canal Point; 1964-65.


After the toe ditch was excavated the water level in well 4 declined and since
then no flooding has been observed.
Water levels in observation wells 1, 2 and 6 that tap aquifer A-1 fluctuate
in concert with the level of the lake, as shown by the hydrographs on figure 41.
The water levels in the aquifer slope eastward away from the lake, thus the flow
is eastward from the lake. Water levels in the wells were slightly affected by
drainage operations in the agricultural area. Well 6, which is closest to the
agricultural area, was affected most by pumping from the drainage canal located
0.7 mile east of the dike.
The chloride content in the lake at site 5 appears to be highest during the
wet periods when water containing high chloride is pumped from the agricultural






REPORT OF INVESTIGATION NO. 58


_1
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-I





IL
0
j
.J




ul

0















MW
-
I,

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z










t
w
N












I'-

W
-J
W


-1





hi
>-
.w
O W



I-

IU
a-


- LAKE
--- WELL 3


.-.- WELL 4
---- WELL 5


Figure 40. Graphs comparing water levels, chloride content, and water
temperature in wells that tap confining bed C-I at site 5 with the
data for the lake, 1964-65.


200 I Iiii i




10-












00 J M A M A 0




1964 EXPLANATION 1