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    Abstract and introduction
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    Purpose and scope and acknowledgment
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    Methods of investigation
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    Hydrology
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    Conclusions
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    Summary
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    References
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        Copyright
            Main

STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES





BUREAU OF GEOLOGY
Robert O. Vernon, Chief






INFORMATION CIRCULAR NO. 59






SEEPAGE TESTS IN L-D 1 BORROW CANAL
AT LAKE OKEECHOBEE, FLORIDA




By
F. W. Meyer and J. E. Hull
U. S. Geological Survey




Prepared by
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
CENTRAL AND SOUTHERN FLORIDA FLOOD CONTROL DISTRICT
and the
BUREAU OF GEOLOGY
FLORIDA DEPARTMENT OF NATURAL RESOURCES


TALLAHASSEE
1969



















V\A, S1


Completed manuscript received
October 19, 1968
Printed by the Florida Department of Natural Resources
Bureau of Geology
Tallahassee







CONTENTS

Page
Abstract . . . . . . . . 1
Introduction . . . . . . . 1
Purpose and scope ........................... 3
Acknowledgments ........................... 3
Methods of investigation ................... ..... 4
Hydrology ...... ................. .... .......... 5
Test 1 ............. ................... 8
Seepage analysis .. .. .. .. .. .. 9
Test 2 . . . . . . ..... 13
Seepage analysis .. .. .. .. . .. .. .. .. 14
Test 3 . . . . . . . ... 20
Seepage analysis .. .. . . .. .. .. .. .. 21
Conclusions ................... ............ 26
Summary . . . . . . . . 28
References . . . . . . .... 31


ILLUSTRATIONS

Figure Page
1 Map of Florida showing area of the investigation . . . 2
2 Map ofthetestsite ... ..................... 3
3 Profile along line A-A' at site no. 1 (Station 180+00, Levee Dl) showing aquifers
and confining beds .... ... .... ............... 7
4 Graphs of water levels in Lake Okeechobee and in the L-D1 Borrow Canal, January
18-March 7, 1968 . . . . . . 9
5 Graphs of water levels in wells 5, 8, 6, 22, and 25 in Aquifer No. 1, January
18-March7, 1968 .. . .. .. .. . .. .. .. 10
6 Graphs of water levels in wells 10, 7, 9, 20, and 23 in Aquifer No. 2, January
18-March7, 1968 . .. .. .. .. .. ... .. 11
7 Graphs of water levels in wells 11, 3, 21, and 24 in Aquifer No. 3, January
18-March 7, 1968 .. .. .. ... . .. ... .. 12
8 Hydraulic profile along line A-A at Site No. 1, January 3, 1968 . ... 13
9 Hydraulic profile along line A-A' at'Site No. 1, January 29, 1968 . .. 15
10 Hydraulic profile along line A-As at'Site No. 1, February 2, 1968 . .. 18
11 Hydraulic profile along line A-A' at Site No. 1, February 19, 1968 . .. 22
12 Map showing contours on the water table south of the L-D1 Canal, February 19,
1968 . . . . . . . 24
13 Graph showing recovery curve of water level in L-D1 Borrow Canal, dashed where
estimated . . . . . . . 26

TABLES

Table Page
1 Summary of the seepage tests ..... . . . 27









SEEPAGE TESTS IN L-D 1 BORROW CANAL
AT LAKE OKEECHOBEE, FLORIDA

By
F. W. Meyer and J. E. Hull

ABSTRACT
Tests were made along Levee D-l and the adjacent Levee D-l borrow canal at
the west side of Lake Okeechobee near Moore Haven, Florida, to determine the
magnitude of the underseepage from the lake. By relating the ground-water
gradients in the vicinity to the amount of pickup in a 3-mile reach of the L-D1
Canal, it was determined that the underseepage factor is about 0.9 cfs per mile
per foot of head between the lake and the canal. The coefficient of
transmissibility of the underlying materials is about 72,000 gpd/ft. The values
are important in the design of a pumping station which will remove increased
underseepage when the lake level is raised several feet.
INTRODUCTION
The U.S. Geological Survey, in cooperation with the Central and Southern
Florida Flood Control District (C&SFFCD) and the Diston Island Drainage
District conducted seepage tests along a 3%-mile reach of the L-D1 Borrow Canal
rimming Lake Okeechobee, as shown on figure 1, near Moore Haven, Florida,
during the period December 18, 1967 through March 7, 1968. The reach of
canal located on the landward side of the Hoover Dike between Culverts No. 1
and 1A, was dug about 1962 to provide fill for raising the elevation of the
Hoover Dike and for construction of a seepage dike along the canal's landward
side, as shown on figure 2.
The tests were conducted at the request of the C&SFFCD to provide field
verification of seepage rates calculated from seepage factors previously
determined by Meyer in an investigation of seepage rates along the Hoover Dike
during the period 1963-66. In a written communication to C&SFFCD on May 6,
1966, Meyer reported that the seepage factor at Site No. 1, figure 3, was
about 1.2 cfs (cubic feet per second) per mile per foot of head between the lake
and the canal. In 1963, the U.S. Army Corps of Engineers recommended
improvements in outlets and canals in the Nine-Mile Canal area to convey both
pumped runoff from the agricultural area and seepage from the lake to a planned
pumping station (S-4) located about 4 miles east of Culvert 1A near Clewiston.
The Corps of Engineers (1963, plate 9) estimated that the average seepage into
the L-D1 Canal from the lake would be about 76 cfs per mile when
corresponding levels of the lake and the canal were at 19 and 13 feet,
respectively. This represents a seepage factor of about 12.7 cfs per mile per foot
of head between the lake and the canal. Because of the wide range between the
reported seepage factors it was deemed important that field tests be performed.






DIVISION OF GEOLOGY


Figure 1. Map of Florida showing area of the investigation.






INFORMATION CIRCULAR NO. 59 3


EXPLANATION
S CANAL
N I DO RVATION WDLLI



w A---A LINE OF PROFILE
SIlo lo-.7








II CA









Figure 2. Map of the Test Site.

PURPOSE AND SCOPE

The purpose of the investigation was to evaluate the two reported seepage
factors by actually measuring the seepage entering the L-D1 Canal as its level was
lowered several feet below that of the lake. The plan was to lower the water level
in the canal by both pumped and gravity outflows to the Diston Island Drainage
District. The hydraulic gradients to and from the canal were to be determined by
utilizing existing observation wells at Site No. 1 (fig. 2). The coefficient of
transmissibility would then be computed by relating the measured outflow to
the ground-water gradients. The seepage factor would then be computed by
relating the total seepage from the lake to the head between the lake and the
L-D1 Canal. The findings of this report should be helpful in evaluating seepage
rates for future drainage projects and in providing basic information on the
methods used to determine seepage factors.

ACKNOWLEDGMENTS

The authors wish to express their appreciation for the cooperation extended
by Messrs. Storch, Taylor, Irons, and Lane of the Central and Southern Florida
Flood Control District, Messrs. Knecht and Brantley of the Diston Island






DIVISION OF GEOLOGY


Drainage District, Messrs. Koperski and Wiesenfeld of the U.S. Army Corps of
Engineers, and Mr. Jensen of Gee and Jensen, Consulting Engineers.
Messrs. Knecht and Springstead of the U.S. Sugar Corp., were instrumental in
initiating the tests and provided liaison and helpful suggestions during the
investigation.
The work was done under the general supervision of C. S. Conover, District
Chief, and the immediate supervision of H. Klein, Subdistrict Chief, of the Water
Resources Division, U.S. Geological Survey.
METHODS OF INVESTIGATION
Prior to the tests, a reconnaissance was made of the area and several meetings
were held with engineers of the C&SFFCD, the Diston Island Drainage District,
and the U.S. Sugar Corp., to arrive at a plan for cooperative assistance during
various phases of the tests. Agreements reached were as follows:
1. Personnel of the U.S. Geological Survey would supervise the tests, collect
and analyze the data, and prepare a report on the findings. Also, they would
replace observation wells 12, 13, and 14 with wells 20, 21, and 22 and install
three additional wells (23-25) about 1,200 feet south of the L-DI Canal in the
existing line of wells at Site No. 1.
2. The Diston Island Drainage District would provide pumping facilities and
manpower to operate the controls in the culverts and furnish about 40 feet of
6-foot culvert for installation beside Culvert 1B.
3. The U.S. Sugar Corp. would install water-level recording instruments on
the observation wells, in the L-DI Canal, and in Lake Okeechobee.
4. The C&SFFCD would obtain permission and provide the necessary
equipment to install the additional culvert, designated herein as Culvert I Ba
beside Culvert 1B.
Most of the data was collected during the period January 18 through March 7,
1968. Discharge from the 3-mile reach of the L-D1 Canal was measured with a
current meter in the 6-foot culverts located at each end of the canal. Culvert 1C,
with bottom invert at 10.2 feet above mean sea level (msl), was used as a
measuring section for determining the gravity flow from the canal, and Culvert
IBa, with bottom invert at 5.0 feet above msl, was used to determine the
pumped flow. A diesel-powered pump, rated at 125 cfs, was used to lower the
water level in the L-DI Canal several feet below that in the lake. Water-level data
were continuously recorded in 14 observation wells, in the L-D1 Canal, and in
the lake during the period January 18 through March 7, 1968, as shown on
figures 4, 5, 6 and 7. Hydraulic profiles were constructed from water level data
for selected days to determine the direction and amounts of seepage into or out
of the L-D Canal, as shown on figures 8, 9, 10 and 11.






DIVISION OF GEOLOGY


Drainage District, Messrs. Koperski and Wiesenfeld of the U.S. Army Corps of
Engineers, and Mr. Jensen of Gee and Jensen, Consulting Engineers.
Messrs. Knecht and Springstead of the U.S. Sugar Corp., were instrumental in
initiating the tests and provided liaison and helpful suggestions during the
investigation.
The work was done under the general supervision of C. S. Conover, District
Chief, and the immediate supervision of H. Klein, Subdistrict Chief, of the Water
Resources Division, U.S. Geological Survey.
METHODS OF INVESTIGATION
Prior to the tests, a reconnaissance was made of the area and several meetings
were held with engineers of the C&SFFCD, the Diston Island Drainage District,
and the U.S. Sugar Corp., to arrive at a plan for cooperative assistance during
various phases of the tests. Agreements reached were as follows:
1. Personnel of the U.S. Geological Survey would supervise the tests, collect
and analyze the data, and prepare a report on the findings. Also, they would
replace observation wells 12, 13, and 14 with wells 20, 21, and 22 and install
three additional wells (23-25) about 1,200 feet south of the L-DI Canal in the
existing line of wells at Site No. 1.
2. The Diston Island Drainage District would provide pumping facilities and
manpower to operate the controls in the culverts and furnish about 40 feet of
6-foot culvert for installation beside Culvert 1B.
3. The U.S. Sugar Corp. would install water-level recording instruments on
the observation wells, in the L-DI Canal, and in Lake Okeechobee.
4. The C&SFFCD would obtain permission and provide the necessary
equipment to install the additional culvert, designated herein as Culvert I Ba
beside Culvert 1B.
Most of the data was collected during the period January 18 through March 7,
1968. Discharge from the 3-mile reach of the L-D1 Canal was measured with a
current meter in the 6-foot culverts located at each end of the canal. Culvert 1C,
with bottom invert at 10.2 feet above mean sea level (msl), was used as a
measuring section for determining the gravity flow from the canal, and Culvert
IBa, with bottom invert at 5.0 feet above msl, was used to determine the
pumped flow. A diesel-powered pump, rated at 125 cfs, was used to lower the
water level in the L-DI Canal several feet below that in the lake. Water-level data
were continuously recorded in 14 observation wells, in the L-D1 Canal, and in
the lake during the period January 18 through March 7, 1968, as shown on
figures 4, 5, 6 and 7. Hydraulic profiles were constructed from water level data
for selected days to determine the direction and amounts of seepage into or out
of the L-D Canal, as shown on figures 8, 9, 10 and 11.






INFORMATION CIRCULAR NO. 59


HYDROLOGY
The investigation was divided into three tests in order to determine the
seepage under different conditions. The first test comprised an evaluation of the
hydrologic conditions during the period December 18 through January 22 when
water flowed from the lake into the 3-mile reach of L-D1 Canal. The second
test involved the lowering of the water level in the canal by gravity drainage
during the period January 24 through February 2. The third test involved the
lowering of the water level in the canal by pumping during the period February
13 through February 20.
The amount of seepage from the lake beneath the 3-mile length of the
Hoover Dike depends primarily on the coefficients of transmissibility of the
aquifers and the hydraulic gradients. The transmissibility is assumed to be
uniform along the reach of dike because the geologic section prepared by the
Corps of Engineers (1961, plate 13) shows that the sub-surface materials at Site
No. 1 are generally similar to those underlying the dike from Culvert 1B to
Culvert 1C.
The transmissibility (T) is defined as the amount of water, in gallons per day,
at the prevailing water temperature, that would pass through a 1-foot wide
section of the full saturated thickness of the aquifer under a unit hydraulic
gradient and is determined from the equation
Q (1)
T=
IL
where Q is the seepage in gallons per day, L is the length of canal affecting the
seepage, in feet, and I is the average hydraulic gradient. The gradient (I) is
determined by the equation
h
I= (2)
d
where 11 is the head, in feet, between the water levels in two observation wells in
the same aquifer at Site No. 1 and d is the distance, in feet, between the wells.
It is assumed that T and L are constant, that flow is steady-state, and that the
hydrologic influence of filtercakes in the lakeside navigation canal and in the
L-DI Canal are uniform. The discharge Qm flowing into or out of the L-D1
Canal is related to the seepage by the equation
Qm QI + Qd + ASm (3)
where QI is the seepage from or into the lake, Qd is the seepage from or into the
Diston Island Drainage District, and ASm is the change in storage in the L-D1
Canal expressed in terms of daily mean discharge. Elements Qm, QI, and Qd are
positive when the direction of seepage is toward the L-D1 Canal and the
discharge is from the canal. ASm is positive when the water level in the L-D1
Canal is falling.






DIVISION OF GEOLOGY


Equations 4 and 5 below express the seepages related to the lake and Diston
Island Drainage District in terms of the coefficient of transmissibility and the
hydraulic gradients (see equation 1) where II is the hydraulic gradient related to
the lake and Id is that related to the drainage district.
Ql = TU (4)

Qd= TLId (5)
Equation 6 below is obtained by substituting equations 4 and 5 in equation 3
and equation 7 is obtained by solving equation 6 in terms of T.
Qm = TL (I + Id) + ASm (6)

T =Qm-ASm (7)
L (1 + Id)
The seepage factor (Se) is defined herein as the rate of seepage per mile length
of recharge section per foot of head between the recharge boundary and the
discharge boundary. It is determined by using the equation

Se = Q (8)
L(h -h2)
where Q is the seepage rate (cfs), L is the length of the recharge section (miles),
hi is the elevation of the water level at the recharge boundary (feet), and h2 is
the elevation of the water level at the discharge boundary (feet).
Figure 3 is a profile across the Hoover Dike at Site No. 1 showing the aquifers
and confining beds. Hydrologic units A-l,. A-2, and A-3 are designated as
aquifers and hydrologic units C-l, C-2 and C-3 are designated as confining beds.
Some seepage, however, occurs through each of these beds but most seepage
occurs through beds A-l, A-2, and A-3 because they are more permeable and are
located close to sources of recharge (the Lake Okeechobee Navigation Canal)
and discharge (the L-D1 Canal).
Bed A-I is chiefly a sandy, marly limestone whose upper surface is
case-hardened. Many small solution holes account for zones of high permeability
in A-l. Bed A-2 is composed mostly of shells and is highly permeable. Bed A-3 is
composed of sand and sandstone and is moderately permeable.
Bed C-1 is composed of black organic muck and is relatively impermeable. Its
confining ability is locally ineffective where it is transected by many canals and
ditches. Bed C-2 is composed of sand and is only slightly less permeable than
beds A-1, A-2, and A-3. Its confining ability is locally ineffective where it is
transected by the deep borrow canals. Bed C-3 is composed of green clay and is
relatively impermeable. Its confining ability is very effective because it has low
permeability and is not breached by the borrow canals. Bed C-3 retards the






INFORMATION CIRCULAR NO. 59


-RANt,
1M0KF911T


Figure 3. Profile along line A-A' at site no. 1 (Station 180+00, Levee DI) showing
aquifers and confining 6eds.

movement of water into and out of bed A-3; therefore seepage through bed A-3
is considered negligible. Most of the seepage beneath the dike at Site No. 1 is
considered to occur through the upper 30 feet of material.
Of equal importance in the analysis of underseepage is the role played by silt
deposits lining the sides and bottoms of the borrow canals. These deposits were
formed chiefly by the settling-out of the fine fractions from the excavated
material and by the accumulation of organic sediments derived from dead
vegetation and from erosion of the surface materials.
Because the level of the lake is usually higher than the water level in the
Diston Island Drainage District, hydrostatic pressure has caused a filtercake to
form on the bottom and walls of the lakeside canal. The buildup of the
filtercake has probably caused a progressive reduction in the seepage from the
lake over a period of 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 aquifer
coefficients is related to hydraulic gradients within the aquifer itself, and not to
gradients influenced by the filtercake.








DIVISION OF GEOLOGY


Figures 4-7 are graphs of fluctuations in water levels at Site No. 1 during the
period January 18-March 7, 1968. Figure 4 is a comparison of the fluctuations
in water levels in Lake Okeechobee with those in the L-DI Canal. The maximum
head attained between the lake and the canal was about 5 feet. Figures 5-7
show the fluctuations in water levels in observation wells tapping the three
aquifers at Site No. 1. The lines representing fluctuations in the wells are coded
by a number of dots so that the line with the least dots represents the well site
nearest to the lake while the line with the most dots represents the well site
farthest from the lake. Water levels in most wells were affected by changes in the
stage of the L-D1 Canal.
A comparison of figure 5 with figure 6 shows that water-level fluctuations in
aquifers A-I and A-2 at comparable distances from the canal were essentially
identical with respect to time and amplitude. Thus both aquifers are
hydraulically connected to the L-D1 Canal and to each other, and therefore
function locally as a single hydrologic unit. A comparison of figure 7 with
figures 5 and 6 shows that water-level fluctuations in aquifer A-3 were less
affected by changes in the stage of the L-D1 Canal. The reduction in the
amplitude of the fluctuations is caused by the confining effect of the overlying
bed C-3. Water levels in wells 23, 24, and 25, located about 1,200 feet south of
the L-DI Canal (fig. 3), were unaffected by changes in the stage of the canal
during the tests due to the effect of constant head in a field ditch located about
450 feet north of the wells.
TEST 1
During the period January 18 through January 22, 1968 the water level in the
L-DI Canal was generally less than 0.2 foot below that of Lake Okeechobee
because of uncontrolled inflow of water from the lake (fig. 4). Lake water
flowed directly into the L-D1 Canal through Culvert 1B (fig. 2) because debris
had lodged in the automatic flap gate and prevented its closure. Normally, the
gate at Culvert 1B would close by differential head produced by higher water
levels in the lake and in the lakeside bay of Diston Island's Pumping Plant No. 1.
During this period Culvert 1C was closed. This condition was observed to have
been in effect since December 18, 1967.
If no seepage occurred from the L-D1 Canal, the water level in the canal
would have reached equilibrium with that of the lake and flow into the canal
would have ceased. The lower head in the canal, however, indicated that the
flow entering the canal through Culvert 1B was roughly equivalent to the total
amount of seepage from the canal into the Diston Island Drainage District along
its 3%-mile reach.
Five measurements of the flow into the canal ranged from 14 to 47 cfs during
the period December 18 through January 22. At times the velocity of flow
varied greatly within a single measurement and once reverse flow was observed.
These variations in flow were caused by head changes attributed to seiche of the








INFORMATION CIRCULAR NO. 59


,Figure 4. Graphs of water levels in Lake Okeechobee and in the L-D1 Borrow
Canal, January 18-March 7, 1968.

lake. The seepage factor and coefficient of transmissibility obtained from this
test is considered less accurate than those obtained from tests 2 and 3 because
head differences were better known and held more constant during the latter
tests.

SEEPAGE ANALYSIS
Hydraulic profiles were constructed to show the distribution of water levels in
the subsurface materials at Site No. 1 at times when the flow into the L-DI
Canal was measured at Culvert 1B. Simultaneous water-level data at the site were
obtained by measuring the depth to water below a point of known elevation in
each well. The water level was then related to mean sea level datum.
The amount of seepage from the canal into the Diston Island Drainage District
depends primarily on the average coefficients of transmissibility of the aquifers
and the hydraulic gradients in the aquifers along the 3%-mile length of the canal.







DIVISION OF GEOLOGY


Figure 5. Graphs of water levels in wells 5, 8, 6, 22, and 25 in aquifer No. 1,
January 18-March 7, 1968.

Figure 8 is a hydraulic profile showing the distribution of heads and
equipotential lines on January 3, 1968. The flow through Culvert B was 14.7 cfs
and 13.9 cfs at 11:45 a.m. and 2:30 p.m., respectively. The average flow was
assumed to be 14.3 cfs, or 9.24 mgd (million gallons per day). It was also
assumed that the water level in the canal did not change.
By estimating the location of a ground-water divide beneath the Hoover Dike
(fig. 8) it was determined that 14.3 cfs flowed from the L-DI Canal into the
district through A, the upper 90 percent of saturated thickness while 1.6 cfs
flowed from the lake through B, the lower 10 percent. Thus, the total seepage
(Q) into the district was 15.9 cfs, or about 10.3 mgd. The hydraulic gradient (I)
was computed by averaging the head (h) between wells 6 and 22 and between
wells 9 and 20, by measuring the distance (d) between the wells and by solving
equation 2 (p. 5) as follows:

Average h 0.56 foot
d 138 feet


EXPLANATION
WCLL WELL

*-- -- -.ESTIMATED RECORD








INFORMATION CIRCULAR NO. 59


EXPLANATION
WELL WELL
10-- -- 20E-....
-**- T RCO.D.
. ...... ESTIMATED RECORD


Figure 6. Graphs of water levels in wells 10, 7, 9, 20, and 23 in aquifer No. 2,
January 18-March 7, 1968.


The coefficient of transmissibility (T) was computed
values of I, Q, and L in equation 1 and solving as follows:
10,300,000 gpd
T = gpd = 135,000 gpd/ft.
(.56 ft.) x (18,810 ft.)
(138 ft.)


by substituting the


The seepage factor (Se) was computed by solving equation 8, and by assuming
that the lake was the recharge boundary and well 23 was the discharge
boundary:

15.9 cfs ,


Se =
3.56 mi. x (13.69 11.15) ft


= 1.8 cfs/mi/tt







EXPLANATION .
WELl WELL

-- ........3- --- --24-

.I.... 3- -2 .. 24- .. -- ...





.I .... ... "- ....


100
018 19 21 '22232425 26 27 2829' 30 31 2 3 4 5 7 8 9 10 II
SJAN 196 FES 198

w 0


,12



crI-

0 12 13 14 IS 167' 17 8 19 I 20 21 22 23 24 25 6 2 6 2 27 28 I 2 3 4 5 6 7
MAR 19NB



Figure 7. Graphs of water levels in wells 11, 3, 21, and 24 in Aquifer No. 3, January
18-March 7, 1968.








INFORMATION CIRCULAR NO. 59


EXPLANATION
FLOW FOR 356 MILE LENGTH --.- GROUND WATER DIVIDE
CUBC FEET PER SECOND (C.F.S)
WELL NUMBER IM DIKE FILL
VWTER LEVEL,FEET ABOVE
MEAN SEA LEVEL
UNCASED PORTION OF WELL
CONFINING BED
AQUIFER SEEPAGE DIKE-A -


RANGEFEET


Figure 8. Hydraulic profile along line A-At at Site No. 1, January 3, 1968.

The solution of equation 8 yields a seepage factor of 1.8 cfs per mile per foot
of head between the lake and well 23. This value exceeds the previous estimated
value of 1.2 by about 50 percent. Part of this difference was due to storage
changes in the canal caused by seiche, and part was due to a nonsteady state of
flow from the canal caused by changing head in the canal and to nonsteady
ground-water levels.

TEST 2

The objective of the second test was to determine the amount of seepage from
the lake when the level of the L-D1 Canal was lowered by gravity flow. On
January 22 the debris in Culvert 1B (fig. 2) was removed and the automatic flap
gate closed. After the gate was closed, the reach of canal became ponded and the
water level declined toward a static level between the water level in the lake and
that in the Diston Island Drainage District (figs. 4-7). On January 24, before
equilibrium was reached, Culvert 1C (fig. 2) was opened and the level of the
canal rapidly declined (fig. 4). During the period January 25 through February
2, the discharge measured through Culvert 1C was as follows:







DIVISION OF GEOLOGY


Date Time Discharge (cfs)
January 25 8:10 a.m. 16
January 26 12:00 p.m. 14
January 29 10:00 a.m. 8.3
February 2 10:45 a.m. 7.2
Water levels in the L-DI Canal (fig. 4) and in observation wells (figs. 5-7) had
nearly stabilized after about a week of gravity flow indicating that a steady-state
flow condition had been essentially attained.
SEEPAGE ANALYSIS
The hydraulic gradients at Site No. 1 on January 29, 1968, as shown on figure
9. just prior to steady-state conditions, were analyzed using the aforementioned
equations.
The hydraulic gradient Ii between wells 10 and 7 was assumed to reflect the
seepage from the lake into the L-DI Canal; and the hydraulic gradient Id
between wells 9 and 20 was assumed to reflect the seepage loss from the L-DI
Canal to the Diston Island Drainage District. Ij and Id were computed using
equation 2.

12.30- 11.65 ft 0.65 ft
I = = 0.00320
203 ft 203 ft
11.31 11.35 ft -0.04 ft
Id = = 0.00029
138 ft 138 ft
The coefficient of transmissibility was computed using equation 7. The
change in canal storage. ASm, was determined to be equivalent to 0.5 cfs; Qm is
8.3 cfs.

Qm- ASm 8.3 cfs 0.5 cfs
T= =
L(11 + Id) 18,810 ft (0.00320 + (0.00029))

= 0.1425 cfs/ft x 0.64632 mgd/cfs
= 0.09210 mgd/ft = 92,100 gpd/ft

The seepage from the lake beneath the Hoover Dike, QI was computed using
equation 4; and the seepage loss from the L-Dl Canal to the district, Qd was
computed using equation 5.
Ql= Tx L x = 92,100 gpd/ft x 18,810 ft x 0.00320

= 5.544 mgd x 1.5472 cfs/mgd


= 8.578 cfs = 8.6 cfs







INFORMATION CIRCULAR NO. 59 15


Qd = Tx L x Id = 92,100 gpd/ft x 18,810 ft x (-0.00029)

= 0.5024 mgd x 1.5472 cfs/mgd

= 0.777 cfs = -0.8 cfs
The analysis was checked using equation 3.

Qm = Q + Qd + ASm
8.3 cfs = 8.6 cfs + (-0.8 cfs) + 0.5 cfs = 8.3 cfs
The seepage factor, Se, was computed using equation 8. L is expressed in
miles, h1 is the elevation of the water level in the lake, and 112 is the elevation of
the water level in the L-D1 Canal.

QIl 8.6 cfs
S e =
L (h1 -h2) 3.56 mi (13.45 11.31) ft.
8.6 cfs cfs/mi
3.56 mi (4 f) 1.1
3.56 mi (2.14 ft) ft


RANGE,FEET


Figure 9. Hydraulic profile along line A-A' at Site No. 1, January 29, 1968.







DIVISION OF GEOLOGY


The results indicate that: () T equals 92,100 gpd/ft, (2) 8.6 cfs seeped from
the lake beneath the Hoover Dike, (3) of the 8.3 cfs measured as discharge from
the L-DI Canal, 7.8 cfs seeped from the lake and 0.5 cfs was related to depletion
of storage in the canal, (4) 0.8 cfs seeped from the L-D1 Canal into the Diston
Island Drainage District, and (5) the seepage factor was 1.1 cfs per mile per foot
of head between the lake and the L-DI Canal.
The aforementioned analysis, however, did not compensate for higher water
levels in the drainage district south of Pumping Plant No. 1. During the test
period. Pumping Plant No. 1 was operating and the water level in the canal south
of the pump was held at about 14 feet above msl. Lacking specific water-level
data in the district between Site No. 1 and Pump Plant No. 1, the hydraulic
gradient between wells 9 and 20, located south of the canal at Site No. 1 (fig. 9)
was assumed to represent the seepage along one-third of the length of the canal
between Culverts IB and IC. A reversed hydraulic gradient equal to that
between wells 9 and 20 was assumed to represent the seepage along the
remaining length. Therefore, seepage along one-third of the distance was from
the canal into the district while seepage along the remaining distance was from
the district to the L-DI Canal. Thus the net result was seepage from the district
into the canal along one-third its length.
The data were reanalyzed using equations 2-8, and the same wells for
hydraulic gradients. However, in equation 5 the element Qd is representative of
the net seepage along the length L as shown in the following equation:

Qd = Tx Id x 2/3 L Tx Id x 1/3 L
= Tx Id (2/3 L- 1/3 L)
T x Id x L
3

The coefficient of transmissibility was computed by substituting Id/3 in
equation 7.

Qm Am 8.3 cfs 0.5 cfs
T= =
L(II + 1/3 Id) 18,810 ft (0.00320 + 0.00029)
3

= 0.1258 cfs/ft x 0.64632 mgd/cfs

= 0.08131 mgd/ft = 81,300 gpd/ft







INFORMATION CIRCULAR NO. 59 17

The seepage from the lake, Ql, was computed using equation 4; and the net
seepage from the Diston Island Drainage District to the L-D1 Canal, Qd, was
computed using a modification of equation 5.


Q= T x L x I= 81,300 gpd/ft x 18,810 ft x 0.00320
= 4.894 mgd x 1.5472 cfs/mgd
= 7.57 cfs = 7.6 cfs
Tx Lx Id 81,300 gpd/ft x 18,810 ft x 0.00029
Qd=
3 3
= 0.1483 mgd x 1.5472 cfs/mgd
= 0.229 cfs = 0.2 cfs


The analysis was checked using equation 3.

Qm=Q1+Qd+ ASm

8.3 cfs = 7.6 cfs + 0.2 cfs + 0.5 cfs = 8.3 cfs
The seepage factor, Se, was computed using equation 8.

QI 7.6 cfs
L(h h2) 3.56 mi (13.45- 11.31) ft
7.6 cfs/mi
=-= 1.0
3.56 mi (2.14 ft) ft
The results of the reanalysis indicate that: (1) T equals 81,300 gpd/ft, (2) 7.6
cfs seeped from the lake beneath the Hoover Dike, (3) of the 8.3 cfs measured as
discharge from the L-D1 Canal, 7.6 cfs seeped from the lake, 0.2 cfs seeped from
the district, and 0.5 cfs was related to depletion of storage in the canal, and (4)
the seepage factor was 1.0 cfs per mile per foot of head between the lake and the
L-D1 Canal.
On February 2, the flow in the canal appeared to reach a steady-state
condition and analysis was made of the hydraulic profile at Site No. 1
(fig. 10).
Again, wells 10 and 7 were used to determine the hydraulic gradient Il and
wells 9 and 20 were used to determine the hydraulic gradient Id.
12.24 11.58 ft 0.66 ft
II = -- = 0.00325
203 ft 203 ft

11.22- 11.28ft -0.06 ft
Id = = = -0.00043
:138 ft 138 ft







DIVISION OF GEOLOGY


RANGE.FEET


Figure 10. Hydraulic profile along line A-A' at Site No. 1, February 2, 1968.
The coefficient of transmissibility was computed using equation 7. The
change in canal storage, ASm, was determined to be equivalent to 0.2 cfs; Qm
was 7.2 cfs.


T= Qm qId)
L (l1-+ ld)


7.2 0.2 cfs
18,810 ft (0.00325 + (-0.00043))


= 0.1320 cfs/ft x 0.64632 mgd/cfs
= 0.08530 mgd/ft = 85,300 gpd/ft

The seepages from the lake, Ql, and into the Diston Island Drainage District,
Qd, were computed using equations 4 and 5.
Q= Tx Lx I = 85,300 gpd/ft x 18,810 ft x 0.00325

=5.215 mgd x 1.5472 cfs/mgd


= 8.07 cfs = 8.1 cfs







INFORMATION CIRCULAR NO. 59 19

Qd = Tx Lx Id = 85,300 gpd/ft x 18,810 ft x 0.00043

= 0.6899 mgd x 1.5472 cfs/mgd

= -1.07 cfs = -1.1 cfs

The analysis was checked using equation 3.

Qm=Q + Qd+ ASm

7.2 cfs = 8.1 cfs + (-1.1 cfs) + 0.2 cfs = 7.2 cfs
Se was computed using equation 8.

SQl 8.1 cfs
Se =
L (h1 -h2) 3.56 mi (13.39- 11.26) ft
8.1 cfs cfs/mi
= 1.07
3.56 mix 2.13 ft ft
cfs/mi
=1.1
ft
The results indicate that: (1) T equals 85,300 gpd/ft, (2) 8.1 cfs seeped from
the lake beneath the Hoover Dike, (3) of the 7.2 cfs measured as discharge from
the L-D1 Canal, 7.0 cfs seeped from the lake and 0.2 cfs was related to depletion
of storage in the canal, (4) 1.1 cfs seeped from the L-D1 Canal into the district,
and (5) the seepage factor was 1.1 cfs per mile per foot of head between the lake
and the L-D1 Canal.
Again the data were reanalyzed to compensate for higher water levels in the
western part of the district. The hydraulic gradients between wells 10 and 7 and
between wells 9 and 20 were used to compute II and Id. As previously described,
the gradient between wells 9 and 20 was assumed to be representative along
one-third of the length of canal and reversed equivalent gradient was assumed to
be representative along the remaining two-thirds of the length of canal.
The coefficient of transmissibility was computed using the following
equation: ASm was determined to be equivalent to 0.2 cfs; Qm was 7.2 cfs.

T Qm-ASm 7.2 0.2 cfs
L (I + Id 18,810 ft (0.00325 + 0.00043)
3 3
7.0 cfs
7 f= 0.1097 cfs/ft
18,810 ft (0.003393)
= 0.1097 cfs/ft x 0.64632 mgd/cfs
= 0.07090 mgd/ft 70,900 gpd/ft







20 DIVISION OF GEOLOGY

The seepages from the lake, Ql, and from the Diston Island Drainage District,
Qd, were computed using equations 4 and 5.
Q = Tx L x I = 70,900 gpd/ft x 18,810 ft x 0.00325

= 4334 mgd x 1.5472 cfs/mgd

= 6.706 cfs = 6.7 cfs

Qd = 1/3 x Tx L x Id = 1/3 x 70,900 gpd/ft x 18,810 ft x 0.00325

= 0.1912 mgd x 1.5472 cfs/mgd

= 0.296 cfs = 0.3 cfs
The analysis was checked using equation 3.
Qm = +Qd + Sm

7.2 cfs = 6.7 cfs + 0.3 cfs + 0.2 cfs = 7.2 cfs
Se was computed using equation 8.

Q1 6.7 cfs
L (hl -h2) 3.56 mi (13.39 11.26) ft
6.7 cfs cfs/mi
= 0.884
3.56 mi x 2.13 ft ft

0.9 cfs/mi
= 0.9
ft
The results indicate that: (1) T equals 70,900 gpd/ft, (2) 6.7 cfs seeped from
the lake beneath the Hoover Dike, (3) of the 7.2 cfs measured as discharge from
the L-DI Canal, 6.7 cfs seeped from the lake, 0.3 cfs seeped from the Diston
Island Drainage District, and 0.2 cfs was related to depletion of storage in the
canal, and (4) the seepage factor was 0.9 cfs per mile per foot of head between
the lake and the L-DI Canal.
TEST 3
The objective of the third test was to determine the seepage beneath the
Hoover Dike when the water level in the canal was pumped down several feet
below that of the lake. On February 2, Culverts 1 and 1C (fig. 2) were closed
and the water level in the canal began to rise (fig. 4) to a static position between
the level of the lake and that of the Diston Island Drainage District. Thus, the







INFORMATION CIRCULAR NO. 59


gates were positioned so that Pumping Plant No. 1 would only draw water from
the 3%-mile reach of L-D1 Canal. On February 6, the C&SFFCD breached the
seepage dike beside Culvert 1B and installed Culvert IBa with bottom invert at
elevation 5.0 feet above msl. During the period of construction (February
6-12), the Diston Island Drainage District intermittently operated an auxiliary
pump rated at 22 cfs at Pumping Plant No. 1 and lowered the water level in the
canal to about 11.6 feet above msl.
On February 13, the district began to lower the L-D1 Canal by pumping Plant
No. 1 at a rate of about 65 cfs. Flow from the canal into the pump bay was
measured at Culvert IBa. On February 16, the pump lost suction while pumping
only 28 cfs. In order to compensate for excessive drawdown and the
accumulation of air in the intake it was necessary to increase the pumping rate
and circulate some of the discharge back into the pump bay through a nearby
gated control.
Water levels in the canal and in observation wells began to approach a
steady-state condition by February 19 (figs. 4-7). However, a 0.5-inch rainfall
occurred during the night of February 18 and the flow from the canal increased
from 26 cfs on February 19 to 30 cfs on February 20. Several more days of
pumping would have been required to reach a steady-state condition with no
significant benefit to the analysis. Therefore, the pumping test was terminated
on February 20 and the data obtained on February 19 at 10:00 a.m. was
assumed to be representative of the steady-state condition.
SEEPAGE ANALYSIS
As previously described, an analysis was made using the hydraulic profile at
Site No. 1 on February 19, as shown on figure 11, and the basic equations.
Wells 10 and 7 were used to compute II, the hydraulic gradient from the lake;
and wells 9 and 20 were used to compute Id, the hydraulic gradient from the
district.

10.44 8.89 ft 1.55 ft
1 203 ft 203 ft
= 0.00764
8.90 8.36 ft 0.54 ft
138 ft 138 ft
= 0.00391







DIVISION OF GEOLOGY


EXPLANATION
FLOW FOR 15 MILE LENGTH B DIKE FILL
CUMC niT Prn SEcoND(CFS.)
WLL MUlRt
WATER LEVEL.EET ABOVE
MEAN SEA LEVEL
UNCASED PORTION OF WELL INCLUC
FROM CHA
CONFIMMI BED
AOUIPEM s
EtoQPOTENTIAL LINE. FEET
ABOVE MEAN SEA LEVEL ArTER TA

A-1 U


RANGE ,FEET


Figure 11. Hydraulic profile along line A-A' at Site No. 1, Feb. 19, 1968.

The coefficient of transmissibility was computed using equation 7; Qm was
26.0 cf; ASm was determined to be equivalent to 1.3 cfs.


T Qm' An
L (I + Id)


26.0 cfs 1.3 cfs

18,810 ft (0.00764 + 0.00391)


= 0.1137 cfs/ft x 0.64632 mgd/cfs

= 0.07349 mgd/ft = 73,500 gpd/ft

The seepages from the lake, QI, and from the Diston Island Drainage District,
Qd, were computed using equations 4 and 5.

Q = Tx Lx 11= 73,500 gpd/ft x 18,810 ft x 0.00764

= 10.56 mgd x 1.5472 cfs/mgd


= 16.338 cfs = 16.3 cfs







INFORMATION CIRCULAR NO. 59


Qd = Tx L x Id = 73,500 gpd/ft x 18,810 ft x 0.00391

= 5.406 mgd x 1.5472 cfs/mgd

= 8.364 cfs = 8.4 cfs
The analysis was checked using equation 3.
m = QlQdd + ASm

26.0 cfs = 16.3 cfs + 8.4 cfs + 1.3 cfs = 26.0 cfs
Se was computed using equation 8.

SQl 16.3 cfs
L (hl- h2) 3.56 mi (13.29- 8.08) ft
16.3 cfs cfs/mi
= 0.879
3.56 mi x 5.21 ft ft
cfs/mi
= 0.9
ft
The results of the analysis indicate that: (1) T equals 73,500 gpd/ft, (2) 16.3
cfs seeped from the lake beneath the Hoover Dike, (3) of the 26.0 cfs measured
as discharge from the L-D1 Canal, 16.3 cfs seeped from the lake, 8.4 cfs seeped
from the Diston Island Drainage District, and 1.3 cfs was related to depletion of
storage in the canal, and (4) the seepage factor was 0.9 cfs per mile per foot of
head between the lake and the L-D1 Canal.
The results were re-evaluated using an average hydraulic gradient from the
district to the canal based on water-level data obtained from 3 staff gages located
in the Diston Island Drainage District along the seepage dike, and from staff
gages at Site No. 1, and at the pumping plants, as shown on figure 12.
The average head between the water level at the six observation points in the
district adjacent to the seepage dike and the water level in the L-D1 Canal was
determined to be 1.12 ft. Because the head at Site No. 1 is related to the
hydraulic gradient between wells 20 and 9, the average hydraulic gradient from
the district was assumed to be related to the above-mentioned average head
adjacent to the seepage dike. Thus, the average hydraulic gradient from the
district Id, was estimated to be 0.00548. Il was previously computed using the
slope between wells 10 and 7.







DIVISION OF GEOLOGY


10.44 8.89 ft
II= f- t = 0.00764
203 ft
Av. head x slope between wells 20 and 9
SHead between L-D1 Canal and District at Site No. 1

1.12 ft x 0.00391 .
= ------- = 0.00548
0.8 ft
The coefficient of transmissibility was computed using equation 7: Qm was
26.0 cfs; ASm was determined to be equivalent to 1.3 cfs.

SQm, Am 26.0 cfs 1.3 cfs
L (II + Id) 18,810 ft (0.00764 + 0.00548)
=0.1000 cfs/ft x 0.64632 mgd/cfs
= 0.06462 mgd/ft = 64,600 gpd/ft


Figure 12. Map showing contours on the water table south of the L-D1 Canal,
February 19, 1968.







INFORMATION CIRCULAR NO. 59


QI, the seepage from the lake, and Qd, the seepage from the Diston Island
Drainage District, were computed using equations 4 and 5.
Ql = T x L x I = 64,600 gpd/ft x 18,810 ft x 0.00764

= 9.285 mgd x 1.5472 cfs/mgd

= 14.37 cfs = 14.4 cfs

Qd = Tx Lx Id = 64,600 gpd/ft x 18,810 ft x 0.00548

= 6.660 mgd x 1.5472 cfs/mgd

= 10.30 cfs = 10.3 cfs
The analysis was checked using equation 3.
Qm = Q1 + Qd + Sm

26.0 cfs = 14.4 cfs + 10.3 cfs + 1.3 cfs = 26.0 cfs
Se was computed using equation 8.

QI 14.4 cfs
L (hl -h2) 3.56 mi (13.29- 8.08) ft
14.4 cfs cfs/mi
= = 0.777
3.56 mix 5.21 ft ft
cfs/mi
= 0.8-
ft

Both analyses in this test evaluated T, the coefficient of transmissibility, for a
smaller thickness of aquifer than in the other tests. In tests 1 and 2, T was
representative of a combined aquifer thickness of about 24 feet while that
obtained in test 3 was only representative of about 22.5 feet. Assuming that the
permeability is uniform, the value of T obtained in test 3 would have to be
adjusted by a factor of 1.06 in order to make a comparison of values obtained in
tests 1 and 2.
Therefore, the adjusted T obtained by gradients at Site No. 1 would be
77,900 gpd/ft rather than 73,500 gpd/ft and the other adjusted T would be
68,500 gpd/ft rather than 64,600 gpd/ft.
Because the test did not reach a steady-state condition, it is highly probable
that the actual value of T would be less than the corrected values. Therefore, it is
assumed that the original computed values are representative of the actual
values.







26 DIVISION OF GEOLOGY


Figure 13 is a composite recovery curve of the water level in the L-D1 Borrow
Canal after pumping had ceased. The curve suggests that, if ponded, the water
level in the L-DI Canal would have reached a static level between the stage of
the lake and that in the district after about one month of normal recovery. The
change in slope of the curve when the water level in the canal exceeded that in
the district suggests that seepage into the canal was derived from both the lake
and the district.

CONCLUSIONS

The results of test 1 are considered unsatisfactory and are disregarded herein.
The results of the tests 2 and 3 are summarized in table 1. Seepage factors
ranged from 0.8 to 1.1 cfs per mile per foot of head between Lake Okeechobee
and the L-DI Canal, and coefficients of transmissibility ranged from 64,600 to
92,100 gpd/ft. The range in the computed values is due chiefly to unsteady state
conditions during test three (due to rainfall) and to lack of detailed information
on hydraulic gradients from the Diston Island Drainage District to the L-D1
Canal during test two. There is, however, a possibility that increased hydrostatic
pressure on the filtercake lining the borrow canals reduced the permeability of
the fitercake during the tests and thus contributed to some of the variation in
values.




APPROXIMATE STAGE IN LAKE OKECCHOEE
13,0"

ESTIMATED STATIC WATER LEVEL IN L-DI CANAL


11.- .D.- S


>^ APPROXIMATE GROUN_-WATERSTAGE IN _TH ._ ______
/ D1STON ISLAND DRAINAGE DISTRICT IN WELLS 23
AND 25 AT SITE NO. I
Ic






0 2 4 6 8 io 12 14 16 I 20 22 24 2 28 30 3o
DAYS SINCE PUMPING CEASED


Figure 13. Graph showing recovery curve of water level in L-DI Borrow Canal,
dashed where estimated.







INFORMATION CIRCULAR NO. 59 27

TABLE 1. SUMMARY OF THE SEEPAGE TESTS

Head, Difference between water levels of the lake and the L-D1 Canal, feet; D, Discharge
from L-D1 Canal measured at either Culvert 1B or 1C, cfs; Se, Seepage factor, cfs per mile of
L-D1 Canal per foot of head between the canal and the lake; and T, Coefficient of
transmissibility, gallons per day per foot.

Results based on hydraulic gradients at Site No. 1:

Seepage (cfs)

Head, D From To gpd/ft
Date feet cfs From Lake District District Se T

01-29-68 2.14 8.3 8.6 0.8 1.1 92,100
02-02-68 2.13 7.2 8.1 1.1 1.1 85,300
02-19-68 5.21 26.0 16.3 8.4 .9 73,500

Results based on hydraulic gradients at Site No. 1 adjusted for higher water levels in the
western part of the Diston Island Drainage District
01-29-68 2.14 8.3 7.6 .4 .2 1.0 81,300
02-02-68 2.13 7.2 6.7 .6 .3 .9 170,900
02-19-68 5.21 26.0 14.4 10.3 .8 164,600

not adjusted to complete saturation.
The adjusted results of tests 2 and 3 (table 1) are considered to be most
representative of the values of T and Se. Thus, estimates of seepage in the area
may be made using the average of 72,300 gpd/ft for the coefficient of
transmissibility and 0.9 cfs per mile per foot of head between the lake and the
L-D1 Canal, as the average seepage factor. For example, when the water level of
the lake is raised to 19 feet above msl and the water level of the canal is lowered
to 11 feet above msl, the seepage from the lake is the product of the seepage
factor (0.9 cfs per mile per foot of head between the lake and the L-D1 Canal)
and the loss in head (8 feet) or 7.2 cfs per mile.
The seepage landward of the L-DI Canal is related to the operational stage of
the canal. The canal can be used to intercept almost all or part of the seepage
from the lake, depending on the stage of the canal and the desired (regulated)
ground-water level in the Diston Island Drainage District adjacent to the canal.
If the stage in the canal is maintained at, or slightly below, the stage of the
water table in the district then significant amounts of seepage from the lake will
be intercepted by the canal. If the stage in the canal is maintained below the
stage of the lake but above that in the district then the seepage into the district
will be proportional to the total seepage from the lake and to the discharge from
the canal. The seepage into the district can be estimated by (1) subtracting the
canal discharge from the estimated seepage beneath the Hoover Dike, or by (2)
computing the seepage using Darcy's law, the hydraulic gradient into the district,
and the coefficient of transmissibility (72,300 gpd/ft).






BUREAU OF GEOLOGY


The distance beyond which no effects will occur due to raising the level of the
lake is governed by the occurrence of ditches or canals which act as hydraulic
boundaries. For instance, during Test 3 the water levels in wells 23-25 located
1,200 feet south of the canal were apparently unaffected by the drawdown in
the L-D1 Canal because of a constant-head recharging field ditch.
The simplest way to control the inland effects of raising the level of the lake is
to maintain the water level in the L-D1 Canal at, or slightly below, the desired
water level in the fields adjacent to the seepage dike (fig. 3). Therefore, the
effects of raising the level of the lake will be chiefly limited to water levels in
aquifers A-I and A-2 beneath the Hoover Dike. However, there will be a
corresponding rise in the artesian pressure in aquifer A-3 beyond the L-D1 Canal
which will produce a slight increase in leakage through confining bed C-3. At
present, this leakage is considered negligible but could become a significant
factor if canals are dug deep enough to penetrate bed C-3.
If the water level in the L-D1 Canal is maintained above that in the adjacent
fields then the water level in the L-D1 Canal will affect the water levels in the
adjacent fields in the same manner as the lake. The inland extent of the effects
of raising the water level in the L-D1 Canal above that in the adjacent fields will
be chiefly limited by the occurrence of a discharging field ditch or canal at a
constant head. If the loss in head across the silt lining the L-D1 Canal is
neglected then the slope of the piezometric surface in aquifers A-1 and A-2
would approach a straight line from the water level in the L-D1 Canal to the
water level at the nearest discharge boundary. There will also be a corresponding
rise in the piezometric surface in aquifer A-3 so that increased upward leakage
through bed C-3 may occur.
SUMMARY
The results of the tests on the L-D1 Borrow Canal indicate that the seepage
factor is about 0.9 cfs per mile. per foot of head between the lake and the canal,
and that the coefficient of transmissibility is about 72,300 gpd/ft. These results
compare favorably with those previously determined by F. W. Meyer in 1966.
Seepage from the lake into the L-D1 Canal is estimated to be on the order of 7.2
cfs per mile when the stage of the lake is 19.0 feet above mean sea level and the
stage of the L-DI Borrow Canal is 11.0 feet above mean sea level. Most of the
seepage will occur through aquifers A-1 and A-2. Seepage losses through aquifer
A-3 are considered negligible.
Seepage landward of the L-D1 Canal is related to the operational stage of the
canal The canal can be used to intercept almost all or part of the seepage from
Lake Okeechobee depending on the ground-water levels desired in the fields
adjacent to the canal. If the stage in the canal is maintained at, or slightly below,
the stage of the water table in the fields then the canal will intercept all
significant amounts of seepage.







26 DIVISION OF GEOLOGY


Figure 13 is a composite recovery curve of the water level in the L-D1 Borrow
Canal after pumping had ceased. The curve suggests that, if ponded, the water
level in the L-DI Canal would have reached a static level between the stage of
the lake and that in the district after about one month of normal recovery. The
change in slope of the curve when the water level in the canal exceeded that in
the district suggests that seepage into the canal was derived from both the lake
and the district.

CONCLUSIONS

The results of test 1 are considered unsatisfactory and are disregarded herein.
The results of the tests 2 and 3 are summarized in table 1. Seepage factors
ranged from 0.8 to 1.1 cfs per mile per foot of head between Lake Okeechobee
and the L-DI Canal, and coefficients of transmissibility ranged from 64,600 to
92,100 gpd/ft. The range in the computed values is due chiefly to unsteady state
conditions during test three (due to rainfall) and to lack of detailed information
on hydraulic gradients from the Diston Island Drainage District to the L-D1
Canal during test two. There is, however, a possibility that increased hydrostatic
pressure on the filtercake lining the borrow canals reduced the permeability of
the fitercake during the tests and thus contributed to some of the variation in
values.




APPROXIMATE STAGE IN LAKE OKECCHOEE
13,0"

ESTIMATED STATIC WATER LEVEL IN L-DI CANAL


11.- .D.- S


>^ APPROXIMATE GROUN_-WATERSTAGE IN _TH ._ ______
/ D1STON ISLAND DRAINAGE DISTRICT IN WELLS 23
AND 25 AT SITE NO. I
Ic






0 2 4 6 8 io 12 14 16 I 20 22 24 2 28 30 3o
DAYS SINCE PUMPING CEASED


Figure 13. Graph showing recovery curve of water level in L-DI Borrow Canal,
dashed where estimated.






INFORMATION CIRCULAR NO. 59 29

The significance of the tests lies not in the precision of the computed seepage
factors and coefficients of transmissibility but in their magnitude and their
relationships to the geology of the area. The reported values of T and Se may be
used to estimate seepage rates in other areas having similar hydrogeologic
conditions, and should result in significant savings in the design and operation of
flood-control works around Lake Okeechobee.






BUREAU OF GEOLOGY


The distance beyond which no effects will occur due to raising the level of the
lake is governed by the occurrence of ditches or canals which act as hydraulic
boundaries. For instance, during Test 3 the water levels in wells 23-25 located
1,200 feet south of the canal were apparently unaffected by the drawdown in
the L-D1 Canal because of a constant-head recharging field ditch.
The simplest way to control the inland effects of raising the level of the lake is
to maintain the water level in the L-D1 Canal at, or slightly below, the desired
water level in the fields adjacent to the seepage dike (fig. 3). Therefore, the
effects of raising the level of the lake will be chiefly limited to water levels in
aquifers A-I and A-2 beneath the Hoover Dike. However, there will be a
corresponding rise in the artesian pressure in aquifer A-3 beyond the L-D1 Canal
which will produce a slight increase in leakage through confining bed C-3. At
present, this leakage is considered negligible but could become a significant
factor if canals are dug deep enough to penetrate bed C-3.
If the water level in the L-D1 Canal is maintained above that in the adjacent
fields then the water level in the L-D1 Canal will affect the water levels in the
adjacent fields in the same manner as the lake. The inland extent of the effects
of raising the water level in the L-D1 Canal above that in the adjacent fields will
be chiefly limited by the occurrence of a discharging field ditch or canal at a
constant head. If the loss in head across the silt lining the L-D1 Canal is
neglected then the slope of the piezometric surface in aquifers A-1 and A-2
would approach a straight line from the water level in the L-D1 Canal to the
water level at the nearest discharge boundary. There will also be a corresponding
rise in the piezometric surface in aquifer A-3 so that increased upward leakage
through bed C-3 may occur.
SUMMARY
The results of the tests on the L-D1 Borrow Canal indicate that the seepage
factor is about 0.9 cfs per mile. per foot of head between the lake and the canal,
and that the coefficient of transmissibility is about 72,300 gpd/ft. These results
compare favorably with those previously determined by F. W. Meyer in 1966.
Seepage from the lake into the L-D1 Canal is estimated to be on the order of 7.2
cfs per mile when the stage of the lake is 19.0 feet above mean sea level and the
stage of the L-DI Borrow Canal is 11.0 feet above mean sea level. Most of the
seepage will occur through aquifers A-1 and A-2. Seepage losses through aquifer
A-3 are considered negligible.
Seepage landward of the L-D1 Canal is related to the operational stage of the
canal The canal can be used to intercept almost all or part of the seepage from
Lake Okeechobee depending on the ground-water levels desired in the fields
adjacent to the canal. If the stage in the canal is maintained at, or slightly below,
the stage of the water table in the fields then the canal will intercept all
significant amounts of seepage.









INFORMATION CIRCULAR NO. 59 31


REFERENCES

Ferris, J. G.
1962 (and others) 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 & Jensen Consulting Engineers, Inc., West Palm Beach, Florida. Report for
Board of Supervisors, Diston Island Drainage District.
Pruit, M. M.,U.S. Army Corps of Engineers
1961 Detail Design Memorandum, Herbert Hoover Dike Levees D-1, D-2 (part), and D-3
(Part): Corps of Engineers report in Central and Southern Florida Project for
Flood Control and other purposes, Part 4, Supplement 14.
1963 General Design Memorandum, Nine-Mile Canal area: Corps of Engineers report on
Central and Southern Florida Project.










FLRD GEOLOSk ( IC SUfRiW


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