A test of flushing procedures to control salt-water intrusion at the W. P. Franklin Dam near Ft. Myers, Florida, and The magnitude and extent of salt-water contamination in the Caloosahatchee River between La Belle and Olga, Florida ( FGS: Information circular 62 )

STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES

BUREAU OF GEOLOGY
Robert O. Vernon, Chief

INFORMATION CIRCULAR NO. 62

A TEST OF FLUSHING PROCEDURES
TO CONTROL SALT-WATER INTRUSION
AT THE W. P. FRANKLIN DAM NEAR FT. MYERS, FLORIDA

AND

THE MAGNITUDE AND EXTENT OF SALT-WATER
CONTAMINATION IN THE CALOOSAHATCHEE RIVER BETWEEN
LA BELLE AND OLGA, FLORIDA

By
Durward H. Boggess
U. S. Geological Survey

Prepared by
U. S. GEOLOGICAL SURVEY
in cooperation with the
BUREAU OF GEOLOGY
FLORIDA DEPARTMENT OF NATURAL RESOURCES,
LEE COUNTY BOARD OF COUNTY COMMISSIONERS
and
U. S. ARMY, CORPS OF ENGINEERS

Tallahassee
1970

Completed manuscript received
March 21, 1969
Printed by the
Florida Department of Natural Resources
Bureau of Geology
Tallahassee

CONTENTS

PART I

A TEST OF FLUSHING PROCEDURES
TO CONTROL SALT-WATER INTRUSION
AT THE W. P. FRANKLIN DAM NEAR FT. MYERS, FLORIDA

Page
Introduction . .... .. .. ... . .. . .. ... .. 1
Proposed testing procedures ......... .... .................. 2
Results of test procedure No.1 ................... ............ 3
Instrumentation ......................... ... ... .... 3
Description . . . . . .... . .. .. ... 3
Data collected .......... .. .......... ............. 3
Analysis of data collected ....... ....................... 8
Summary and conclusions ................... ..... ....... 13
References ........... .............. .... .............. 15

ILLUSTRATIONS

Figure Page
1. Map of Lee County, Florida, shows location of W. P. Franklin Dam . 2
2. Plan and section views of the lock chamber at the W. P. Franklin Dam, S-79,
Caloosahatchee River, showing location of recording and nonrecording instruments. 4
3. Graph showing variation in specific conductance at C-3 during downstream gate
openings of 4, 6, and 8 feet .... .................. ......... 5
4. Graph showing variation in specific conductance at CM-1 during downstream gate
openings of 4, 6, and 8 feet ............. ...... ....................... 6
5. Graph showing variation in specific conductance at Stations C-3 and CM-1 during
the 6-foot opening of the downstream gate. . ... . ... 7
6. Graph showing the variation in specific conductance at C-3 as related to a series of
events. ... . .. . .. . .. ... .. . 10
7. Graph showing the variation in specific conductance at C-1 as related to lockages
during the period March 4-6, 1968 . . . . . . 11
8. Graph showing variations in base level specific conductance at C-1, 1966-1968 and
discharge from the W. P. Franklin Dam, 1966-1967 . ..... 12

TABLES

Page
1. Pre-test quality of water at the W. P. Franklin Dam . . . . 8
2. Discharges through locks at W. P. Franklin Dam during flushing tests .......... 8
3. Time and volume of water required to partly flush salty water from lock chamber 8

PART II

THE MAGNITUDE AND EXTENT OF SALT-WATER
CONTAMINATION IN THE CALOOSAHATCHEE RIVER BETWEEN
LA BELLE AND OLGA, FLORIDA

Page
Abstract ......................................... 17
Introduction ........................................ 17
Data-collection procedures ................................ 19
Vertical distribution of chlorides in river water .... . . .... 19
Upstream extent of salt-water contamination, April-May, 1968 ............ 28
Comparison with previous records ............................ 32
Conclusions .......................................36
References ...... ........... ....................... 39

ILLUSTRATIONS

Figure Page
1. Map of Lee County, Florida, showing location of W. P. Franklin Dam . 18
2. Map of the Caloosahatchee River between Olga and La Belle showing locations of
sampling lines ................... ............. 20
3. Graph showing the vertical distribution of chloride in water from the center of the
river at lines 1 and 4 on April 30 and May 21, 1968 . . . ... 25
4. Graph showing the vertical distribution of chloride in water from the center of the
river at lines 7 and 10 on April 30 and May 21, 1968 . . ..... 26
5. Graph showing the vertical distribution of chloride in water from the center of the
river at lines 13, 17, 21, and 25 on April 30 and May 21, 1968 . ... 27
6. Graph showing chloride content of river water at a depth of about 1 foot, as
related to distance upstream from the W. P. Franklin Dam, April 30 and
May 21, 1968. .... ............................ 29
7. Graph showing chloride content of river water near the bottom of the river, as
related to distance upstream from the W. P. Franklin Dam, April 30 and
May21,1968 ................................... 30
8. Graphs showing chloride content of river water on May 19, 1967 and April 30,
1968, as related to distance upstream from the W. P. Franklin Dam ...... .33

TABLES

Page
1. Chloride content of water from the Caloosahatchee River upstream from the W. P.
Franklin Dam, April 30 and May 21, 1968, mg/ . . . ..... 21
2. Miscellaneous measurements of chloride concentrations (mg/1) in the
Caloosahatchee River upstream from the W. P. Franklin Dam . ... 35

A TEST OF FLUSHING PROCEDURES
TO CONTROL SALT-WATER INTRUSION
AT THE W. P. FRANKLIN DAM NEAR FT. MYERS, FLORIDA

by
Durward H. Boggess

INTRODUCTION

During low-flow periods, salty water from the tidal part of the Caloosahatchee
River moves upstream during boat lockages at the W. P. Franklin Dam near Ft.
Myers, Florida, as shown on figure 1; Salty water enters the lock chamber
through openings of the downstream sector gates which separate tidal and fresh
water; when the upstream gates open, some of the salty water moves into the
upper pool, probably as a density current. Repeated injections of salty water
:cause a progressive increase in the salinity of the upstream water. The salty water
moves upstream within the deeper parts of the river channel as far as 5 or more
miles above the lock. Some mixing of the high-chloride deeper water and the
fresher shallow water occurs in the affected reach above the lock, probably as a
result of wind and waves, and turbulence created by boat traffic.
During extended periods of low-flow, the chloride content of the shallow
water increases well beyond the recommended limit of 250 mg/l (milligrams per
liter) for drinking water established by U.S. Public Health Service (1962). For
example, near the end of the dry season in May 1967 the chloride content of
river water near the intake structures for the Ft. Myers and Lee County water
systems, about /4 mile upstream from the lock, was about 500 mg/l. In early
March, 1968, the chloride content of river water near the intake structures was
about 250 mg/1.
The present and planned use of water from the controlled reach of the river
for municipal supply purposes has led to a coordinated effort by federal, state,
and local agencies to develop an effective solution to the problem of salt-water
intrusion through the lock chamber. Plans were developed for conducting several
tests to determine if changes in locking procedures would effectively reduce or
eliminate the problem. Testing procedures were agreed upon at a meeting
attended by officials of the U.S. Corps of Engineers, the Central and Southern
Florida Flood Control District, the United States Geological Survey, Lee
County, City of Ft. Myers and consulting engineers for the county and the city.
This report was prepared in cooperation with Lee County and the Division of
Geology, Florida Board of Conservation.

2 BUREAU OF GEOLOGY

PROPOSED TESTING PROCEDURES

The following three tests were proposed:
Test I. Flushing of salt water from the lock chamber by controlled opening
of the downstream sector gates and full opening of the upstream sector gates,
prior to lockages.
Test 2. Performing lockages on a scheduled time basis for all pleasure craft,
instead of on signal.
Test 3. Flushing of salt water from the lock chamber during lockages by
controlled opening of both upstream and downstream sector gates.

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INFORMATION CIRCULAR NO. 62

Because of the anticipated high manpower and equipment requirements
needed for conducting test 3, it was believed that the results of test 1 would be
of value in establishing these requirements and would be helpful in determining
the necessity for conducting test 3.
A detailed summary of the test conducted on'March 5, 1968, is presented
here, as are comments concerning proposed tests 2 and 3.

RESULTS OF TEST PROCEDURE NO. 1

INSTRUMENTATION

Three conductivity recorders were operated at locations designated as C-1,
C-2, and C-3 in figure 2. The cell for each recorder was placed 1 foot above the
bottom, at an altitude of 13 feet below mean sea level. In addition, a
non-recording conductivity meter was operated at the fire hose station shown as
CM-1 on figure 2. The cell for this meter was maintained at 13 feet below mean
sea level during most of the test.

DESCRIPTION OF THE TEST

Conductivity and discharge measurements were made during each of the
openings of the downstream sector gates of 4, 8 and 6 feet respectively. A repeat
of the 4-foot opening was made after the 6-foot opening to verify results
obtained from the initial 4-foot test. Prior to each opening salt water was
allowed to enter the lock chamber either as a result of normal lockages or by
opening the downstream lock gates. No attempt was made to stabilize conditions
in the lock chamber, only to insure that salt water was present. The upstream
lock gates were fully opened before the controlled opening of the downstream
lock gates.

DATA COLLECTED

Prior to the beginning of the test and following an overnight period of
stabilization, water samples for conductance and chloride analyses were obtained
at C-1, C-2, and C-3. This information is summarized in table 1.
Data obtained from C-3 during each of the downstream gate openings are
presented in figure 3. Similarly, data from CM-1 are presented in figure 4. For
comparison, data obtained from both stations during the 6-foot gate openings
are given in figure 5.
Discharge measurements made at the center of the lock chamber during the
test are summarized in table 2.

INFORMATION CIRCULAR NO. 62

Because of the anticipated high manpower and equipment requirements
needed for conducting test 3, it was believed that the results of test 1 would be
of value in establishing these requirements and would be helpful in determining
the necessity for conducting test 3.
A detailed summary of the test conducted on'March 5, 1968, is presented
here, as are comments concerning proposed tests 2 and 3.

RESULTS OF TEST PROCEDURE NO. 1

INSTRUMENTATION

Three conductivity recorders were operated at locations designated as C-1,
C-2, and C-3 in figure 2. The cell for each recorder was placed 1 foot above the
bottom, at an altitude of 13 feet below mean sea level. In addition, a
non-recording conductivity meter was operated at the fire hose station shown as
CM-1 on figure 2. The cell for this meter was maintained at 13 feet below mean
sea level during most of the test.

DESCRIPTION OF THE TEST

Conductivity and discharge measurements were made during each of the
openings of the downstream sector gates of 4, 8 and 6 feet respectively. A repeat
of the 4-foot opening was made after the 6-foot opening to verify results
obtained from the initial 4-foot test. Prior to each opening salt water was
allowed to enter the lock chamber either as a result of normal lockages or by
opening the downstream lock gates. No attempt was made to stabilize conditions
in the lock chamber, only to insure that salt water was present. The upstream
lock gates were fully opened before the controlled opening of the downstream
lock gates.

DATA COLLECTED

Prior to the beginning of the test and following an overnight period of
stabilization, water samples for conductance and chloride analyses were obtained
at C-1, C-2, and C-3. This information is summarized in table 1.
Data obtained from C-3 during each of the downstream gate openings are
presented in figure 3. Similarly, data from CM-1 are presented in figure 4. For
comparison, data obtained from both stations during the 6-foot gate openings
are given in figure 5.
Discharge measurements made at the center of the lock chamber during the
test are summarized in table 2.

WEST EAST

- DOWNSTREAM

UPSTREAM -

C-2

- GATE
TIDAL ONOLIT

(NON-RECORDING)
C-3 CM-I

ALTITUDE 10 FEET

C-I
ABOVE MEAN SEA LEVEL.

WATER LEVEL
GATE
MONOLITH
ALTITUDE 14 FEET BELOW MEAN SEA LEVEL

I-
blal
0.

a
<>o

0 50 100 150 FEET
HORIZONTAL SCALE

Figure 2. Plan and section views of the lock chamber at the W. P. Franklin Dam, S-79, Caloosahatchee River, showing
location of recording and noiirecording instruments.

! E 10 FEET

EAST

WEST

INFORMATION CIRCULAR NO. 62

12,500

-GATE OPEN 4 FEET

U)
o

0
i
07

U6
0

U)
05

w
0 5

0
o

03
Q
2

03

UJ
v>

TIME,MINUTES SINCE GATE OPENED

Figure 3. Graph showing variation in specific conductance at C-3 during
downstream gate openings of 4, 6, and 8 feet.

GATE OPEN 8 FEET

BUREAU OF GEOLOGY

OPEN 4 FEET

OPEN 6 FEET

\GATE OPEN 8 FEET

OPENED TO
FEET

TIME, MINUTES SINCE GATE OPENED

Figure 4. Graph showing variation in specific conductance at CM-1 during
downstream gate openings of 4, 6, and 8 feet.

INFORMATION CIRCULAR NO. 62

\-RECORDER C-3

CM-1

GATE OPENED TO
.8__/ 8 FEET

10 20 30 40 50 60 70
TIME,MINUTES SINCE GATE OPENED

Figure 5. Graph showing variation in specific conductance at Stations C-3'and
CM-1 during the 6-foot opening of the downstream gate.

BUREAU OF GEOLOGY

TABLE I. PRE-TEST QUALITY OF WATER AT THE W. P. FRANKLIN DAM

Station

C-I

C-2

C-3

Sample
depth

Surface
Bottom
Surface
Bottom
Surface
Bottom

Conductance
(micromhos)

1,600
1,600
10,000
19,000

4,400

Chloride
(mg/l)

345
350
3,640
7,150
490
1,140

TABLE 2. DISCHARGES THROUGH LOCKS AT W. P. FRANKLIN DAM

Gate Opening
(feet)

Head difference
(feet)

ANALYSIS OF DATA COLLECTED

It appears from figures 2 and 3 that flushing of heavy concentrations of salt
water from the lock chamber can be accomplished at each of the gate openings
tested. The time and volume of flushing water required to reduce the
conductivity of water at the center of the lock chamber, C-3, to 2000
micromhos (assumed to represent an acceptable value of conductivity under
present conditions) is shown on table 3.

TABLE 3. TIME AND VOLUME OF WATER REQUIRED TO PARTLY
FLUSH SALTY WATER FROM LOCK CHAMBER

Gate Opening
(feet)

8
6
4

Time
(minutes)

Volume
(acre feet)

As indicated by table 3, at the 8-foot gate opening considerably less time and
a smaller volume of water was required to accomplish the same flushing action as
the smaller gate openings. This suggests that flushing with larger gate openings
may be even more effective.

Discharge
(cfs)

861
1,190
1,510

af/min

1.19
1.64
2.08

INFORMATION CIRCULAR NO. 62

Obviously, additional time and greater volumes of water would be required to
completely flush the lock chamber because the values presented refer to
conditions at the center. However, it is estimated that an additional discharge
time of 6 to 8 minutes would be needed to completely flush the lock chamber at
the 8-foot gate opening. Assuming that the total time would be 15 minutes, then
about 31 acre-feet of water would be required to flush the lock chamber. At 11
lockages per day (average for Jan.-Feb.1968), the volume of water needed
would be about 340 acre-feet, which is equivalent to an average daily discharge
rate of about 170 cfs.
Certain other aspects of the problem warrant consideration. Although salt
water can be flushed from the lock chamber before each lockage, this does not
prevent the reentry of salt water as the downstream sector gates are opened to
admit eastbound boats. The reentry of salt water is clearly indicated in figure 6,
which shows the sequence of events during an eastbound lockage following the
flushing of the lock chamber at the 8-foot gate opening. Salt water reached the
center of the lock chamber within 3 minutes of the time that the water level in
the chamber reached tide level. This would indicate a rate of movement along
the bottom of about 75 feet per minute. In a subsequent measurement between
C-3 and CM-1, the rate of movement was about 60 feet per minute.
Opening the upstream gates normally allows salt water to move from the lock
chamber into the upper pool where conductivity is recorded at station C-l, as
shown in figure 7. Although a precise correlation between peak conductance
values at C-1 and lockages does not exist, the general relationship is readily
apparent because high values are recorded only after periods of lock operations.
The rapid increase and subsequent decrease in conductance values at C-1 indicate
that salty water moves to, and beyond the recorder location. All salty water
injections are not recorded because the deeper channel (24 feet below m.s.1.)
about 100 feet north of the station allows some of the salt water to bypass the
recorder. Thus, the lower conductance values shown for March, on figure 7, may
not be entirely the results of the flushing tests. These conditions should be more
carefully evaluated if flushing procedures are to be adopted.
A second aspect of the problem is related to the quality of water available in
the upstream reach of the river. As shown in figure 8, the specific conductance
of the upstream water is less than 600 micromhos (less than 70 mgl/ of chloride)
during periods when discharge generally exceeds 400 cfs. Conversely, during
extended periods of low discharge, the repeated injections of salty water through
the lock chamber causes a progressive increase in base level conductance values.
The term "base level" refers to the lowest stabilized conductance values
recorded following a series of peak values recorded during the period of lock
operation as shown in figure 7.
Although discharge records are not yet available for the period October 1967
through March 1968, it may be inferred from figure 8 that low-flow conditions
persisted for several months prior to the test of March 5,1968.

SPECIFIC CONDUCTANCE, THOUSANDS OF MICROMHOS
I'll--- 11----11 1 --MIMI_ -1---- ---- I---1- I g- --- ,----1-1.-oi
0
S-- DOWNSTREAM GATE OPENING

WATER IN LOCK CHAMBER TIDE
LEVEL
BOAT ENTERS LOCK CHAMBER
| GOING EAST
0
-DOWNSTREAM GATES CLOSING

o --DOWNSTREAM GATES
g 0 CLOSED
S-UPSTREAM GATE OPENING

I 3DOS -WATER IN CHAMBER REACHES O
o- UPSTREAM LEVEL
S0 -BOAT LEAVES LOCK
8 --UPSTREAM GATES CLOSING
--- UPSTREAM GATES CLOSED

| 0
0o
0 aI

MARCH 4, 1968

MARCH 5,1968

MARCH 6,1968

Figure 7. Graph showing the variation in specific conductance at C-1 as related to lockages during the period March 4-6, 1968.

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1966 1967 1968

Figure 8. Graph showing variations in base level specific conductance at C-l, 1966-1968 and discharge from the W. P.
Franklin Dam, 1966-1967.

INFORMATION CIRCULAR NO. 62

The base level conductance at that time was 1600 micromhos (about 350 mg/l
of chloride) which was considerably higher than that for a comparable period in
1967. If this trend continues over the next several months, the problem of salty
water in the reach of the river from which municipal supplies are obtained will
be of greater magnitude than that in 1967. Although the salinity generally
decreases in the upstream direction, contamination was evident at Alva, about 5
miles upstream, where measurements made between February 1, 1968 and April
12, 1968 showed a progressive increase in chlorides from 170 mg/1 to 585 mg/1
for water in the deeper part of the river.
The point of the preceding discussion is that the chloride content of the water
in the river upstream from the lock had already (March 1968) reached an
undesirable level, and that no effective reduction in these values can be expected
until sufficient quantities of water are available for flushing the contaminated
reach. Inasmuch as the required large quantities of water are not available,
corrective action at the present time can be directed only toward preventing
further encroachment of salt water.

SUMMARY AND CONCLUSIONS

It has been demonstrated from the results of test 1 that salt water can be
flushed from the lock chamber prior to lockages. This can be accomplished at
each of the gate openings of 4, 6 and 8 feet. An opening of 8 feet or more
appears preferable because of the smaller volume of water required and shorter
discharge time involved. An optimum gate opening should be developed by
further testing if this procedure is to be followed. The problem created by the
reentry of salt water into the lock chamber during eastbound lockages also
requires additional study.
Although the flushing procedures may prove effective, it is questionable
whether sufficient quantities of water will be available when needed. For
example, assuming that the volume of water needed is about 340 acre-feet per
day (170 cfs), then more than 10,000 acre-feet would be required for a 30-day
period. The loss of this quantity of water from river storage probably would
cause an excessive lowering of the river level. Furthermore, unpublished
Geological Survey discharge records from the Franklin Dam indicate a period of
68 consecutive days between March and June 1967 when no water, other than
lockage and leakage, was discharged, and an extension of this period to 77
consecutive days when discharge was less than 170 cfs. This long period of low
flow may represent near extreme conditions. However, shorter periods of limited
discharge on an annual basis appears to be a certainty. Thus the availability of
water required for flushing' should be assured if these procedures are to be
adopted.
Considering present (1968) salinity conditions and in view of the available
knowledge concerning the upstream movement of salt water, it would be
advisable to proceed with test No. 2 (scheduling lockages on a time basis), at the

BUREAU OF GEOLOGY

earliest convenient date. This test should be conducted over a period of several
weeks, and possibly continued until the end of the dry season if the procedure
indicates significant benefit. The recording instrument at C-1, for which a large
amount of background data is available, will be the principal source of
information for evaluating the effects of test 2. A second conductivity recorder
will be installed between the upstream lock gates and C-1 to provide
supplemental information.
The principal objection to procedure in test No. 3 has been the potential
danger to boats and boating personnel in moving water through the lock
chamber while boats are moored. However, the procedure may have considerable
merit in providing a solution to the problem of salt-water reentry during
eastbound lockages, as established by test 1. It is suggested that a combination
of the procedures followed in test 1 and those proposed in test 3 may be
effective in reducing the movement of salty water upstream through the lock
chamber.
As indicated in test 1, relatively large downstream gate openings are preferable
because of the smaller volume of water and lower time requirements. The high
water velocities associated with the large gate openings would present potential
danger to boat traffic if the procedures of test 3 alone were followed. However,
a combination of procedures as outlined below may provide a workable solution.
I. Lockages to the west: Flush lock chamber after each lockage using
procedures developed in test 1. This would eliminate intrusion of salt water
resulting from westbound lockages.
2. Lockages to the east: Maintain some flow through lock chamber as boat
enters and is secured. Continue discharge through the chamber as upstream gates
are opened and boat moves upstream. Repeat flushing procedure as in 1 above.

The feasibility of using these procedures is subject to testing. Some benefit
may be derived by selecting gate openings which present little additional hazard
to boat traffic, considering the turbulence already created by opening the
upstream sector gates while raising the water level in the lock chamber.
It is generally concluded that the quantities of salt water moving upstream can
be effectively reduced by adopting changes in locking procedures. Flushing the
lock chamber as described in test I theoretically could result in a 50 percent
reduction, whereas a combination of procedures would be even more effective in
controlling salt-water intrusion. Under the present circumstances it appears
unlikely that complete control and prevention of upstream salt water movement
can be accomplished from a change in procedures as described; nor does it
appear that complete control ii entirely necessary if measures are started early in
the dry season at the first indications of salt-water intrusion.

INFORMATION CIRCULAR NO. 62 15

REFERENCE
U.S. Public Health Service
1962 Public Health Service drinking water standards : Publication No. 956, p. 7.

THE MAGNITUDE AND EXTENT OF SALT-WATER
CONTAMINATION IN THE CALOOSAHATCHEE RIVER BETWEEN
LA BELLE AND OLGA, FLORIDA

By
Durward H. Boggess

ABSTRACT
Repeated injections of salt water through the lock chamber at the W. P.
Franklin Dam causes a progressive increase in the chloride content of water in
the fresh water reach of the Caloosahatchee River during low-flow periods.
Vertical profiles in the contaminated reach of the river show essentially the same
chloride content of the water from the surface to a depth of about 12 feet and
consistently higher concentrations at greater depths. The chloride content of the
water in the deep and shallow zones decreases with increased distance upstream
from the dam.
In the deeper parts of the river channel, the upstream limit of water
containing 250 mg/l (milligrams per liter) of chlorides was 11.4 miles from the
Sdam in May 1968. At shallow depths, the upstream limit of water containing
250 mg/1 of chlorides was 5.3 miles from the dam in May 1967 and 4.7 miles
from the dam in April 1968.
INTRODUCTION
Previous studies have shown that during low-flow periods, salt water from the
tidal reach of the Caloosahatchee River below the W. P. Franklin Dam (S-79)
moves into the fresh-water section of the river above the dam as a result of boat
lockages (Boggess, 1968). Each opening of the upstream lock gates allows the
upstream movement of salt water which had entered the lock chamber during
the previous opening of the downstream lock gates. These repeated injections of
salt water cause a progressive increase in the chloride content of river water
upstream from the dam. The higher density salt water which enters along the
channel bottom moves upstream along the bottom as a density current.
The primary purpose of this report is to evaluate the effects of the repeated
injections of salt water. Of particular interest is the upstream extent of
contamination under these conditions. Measurements of conductivity, and
determinations of the chloride content of water samples obtained during
traverses of the river on April 30 and May 21, 1968 form the basis for this
report, although other information relating to salt-water contamination of the
river is included. Salt-water contamination of the river is of great concern to
water managers who require low chloride concentrations in water for municipal
or for irrigation uses. The location of the area is shown on figure 1.
The U.S. Army Corps of Engineers requested and provided financial support
for the river traverses and for the preparation of this report. Other information

.`

9,

C"
0

Figure 1. Map of Lee County, Florida, showing location of W. P. Franklin Dam.

HENDRY
FORT MYERS COUNTY

LEE
)UNTY _--

I

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! i i

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INFORMATION CIRCULAR NO. 62

was obtained as apart of the current cooperative program of the U.S. Geological
Survey with Lee County and the Division of Geology, Florida Board of
Conservation.
The author is indebted to the Florida Board of Conservation for the able
assistance of H. J. Woodard, Division of Water Resources and Conservation and
C. R. Sproul, Division of Geology, for obtaining water samples and
measurements between La Belle and the Lee-Hendry County line on April 30,
1968; and to the Division of Salt Water Fisheries for providing a boat and the
services of D. N. Ellingsen.
DATA-COLLECTION PROCEDURES
Two traverses of the Caloosahatchee River upstream from the W. P. Franklin
Dam were made on April 30 and May 21, 1968. The first traverse, covering a
distance of 18 miles, was divided into 2 sections requiring the use of separate
teams and equipment. One team worked downstream from the dam. Water
samples were collected at the surface and the bottom at the center of the river
and from similar depths at points 100 to 200 feet from each bank; thus, each set
of samples was obtained along a line normal to the direction of flow. The
locations of the lines are shown on Figure 2. During the first traverse,
conductivity measurements were made on 223 water samples as collected; 37
were retained for laboratory analysis of chloride content. In addition, a
continuous surface to bottom (vertical) conductivity profile was made at the
center of the river at each of lines 1 through 25.
The second traverse, on May 21, 1968, was made by a single team working
upstream from the dam for a distance of about 12 miles. Procedures and
sampling locations were the same as those of the first traverse except that fewer
samples were obtained near the river banks. Specific conductance measurements
were made on 142 water samples as collected, and 29 were retained for analysis
of chloride content. Vertical conductivity profiles were made at the center of
lines 1 through 32.
The results obtained for all samples collected during both traverses are
summarized in table 1. The conversion of specific-conductance measurements to
chloride content in mg/1 was made largely by developing correlation curves for
each conductivity instrument, based on chloride values determined in the
laboratory for the river-water samples. Only the underlined values in table 1,
which represent laboratory analyses, should be considered precise.
VERTICAL DISTRIBUTION OF CHLORIDES IN RIVER WATER
The vertical distribution of chlorides in water at selected locations on April 30
and May 21, 1968, is given in figures 3, 4 and 5. Although the profiles shown
represent only a fraction of the total number obtained during the 2 traverses
they illustrate the general pattern that was found at all locations.

. .. ..~ .. UPPER SECTION

Figure 2. Map of the Caloosahatchee River between Olga and La Belle showing locations of sampling lines.

INFORMATION CIRCULAR NO. 62

was obtained as apart of the current cooperative program of the U.S. Geological
Survey with Lee County and the Division of Geology, Florida Board of
Conservation.
The author is indebted to the Florida Board of Conservation for the able
assistance of H. J. Woodard, Division of Water Resources and Conservation and
C. R. Sproul, Division of Geology, for obtaining water samples and
measurements between La Belle and the Lee-Hendry County line on April 30,
1968; and to the Division of Salt Water Fisheries for providing a boat and the
services of D. N. Ellingsen.
DATA-COLLECTION PROCEDURES
Two traverses of the Caloosahatchee River upstream from the W. P. Franklin
Dam were made on April 30 and May 21, 1968. The first traverse, covering a
distance of 18 miles, was divided into 2 sections requiring the use of separate
teams and equipment. One team worked downstream from the dam. Water
samples were collected at the surface and the bottom at the center of the river
and from similar depths at points 100 to 200 feet from each bank; thus, each set
of samples was obtained along a line normal to the direction of flow. The
locations of the lines are shown on Figure 2. During the first traverse,
conductivity measurements were made on 223 water samples as collected; 37
were retained for laboratory analysis of chloride content. In addition, a
continuous surface to bottom (vertical) conductivity profile was made at the
center of the river at each of lines 1 through 25.
The second traverse, on May 21, 1968, was made by a single team working
upstream from the dam for a distance of about 12 miles. Procedures and
sampling locations were the same as those of the first traverse except that fewer
samples were obtained near the river banks. Specific conductance measurements
were made on 142 water samples as collected, and 29 were retained for analysis
of chloride content. Vertical conductivity profiles were made at the center of
lines 1 through 32.
The results obtained for all samples collected during both traverses are
summarized in table 1. The conversion of specific-conductance measurements to
chloride content in mg/1 was made largely by developing correlation curves for
each conductivity instrument, based on chloride values determined in the
laboratory for the river-water samples. Only the underlined values in table 1,
which represent laboratory analyses, should be considered precise.
VERTICAL DISTRIBUTION OF CHLORIDES IN RIVER WATER
The vertical distribution of chlorides in water at selected locations on April 30
and May 21, 1968, is given in figures 3, 4 and 5. Although the profiles shown
represent only a fraction of the total number obtained during the 2 traverses
they illustrate the general pattern that was found at all locations.

INFORMATION CIRCULAR NO. 62 21

Table 1. Chloride content of water from the Caloosahatchee River upstream from
the W. P. Franklin Dam, April 30 and May 21, 1968, mg/1.

(Notel Chloride contents are based on conductivity-chloride relationships for each instrument used.

Underlined values are laboratory analyses. Numbers in parenthesis indicate approximate depth from
which sample was obtained.)

Location North or West bank Center line South or east bank

April 30 May 21 April 30 Hay 21 April 30 Hay 21

Line I Surface 370 235 370 248 370 235
Bottom 3260 (22) 900(22) 3580 (22) 99 (23) 415 (14) 255(14)
Line 2 Surface 350 230 350 230 350 230

Bottom 550 (16) 1300 (24) 3500 (12) 1420 (23) 3100 (21) 695 (21)
Line 3 Surface 350 230 350 230 350 230

Bottom 2945 (21) 745 (21) 2850 (21) 1050 (22) 1050 (18) 1100 (22)
Line 4 Surface 350 230 350 232 350 230

Bottom 1700 (21) 235 (15) 2910 (22) 1275 (23) 390 (12) 1350 (25)
Line 5 Surface --- 230 350 Z30 350
Bottom 2975 (25) 260 (20) 2975 (24) 1700 (26) 2880 (23) 1560 (25)
Line 6 Surface --- --- 350 230 --- 230
Bottom 413 (14) 230 (14) 2450 (22) 1410 (24) 2450 (23) 1575 (24)

Line 7 Surface 325 220 322 220 325 220
Bottom 2375 (24) 1600 (25) 2475 (24) 1700 (26) 325 (9) 230 (7)

Line 8 Surface 325 225 325 225 --- 230
Bottom 2100 (23) 235 (11) 2375 (26) 1700 (28) 2300 1675 (27)
Line 9 Surface --- 220 302 220 --
Bottom 2100 (25) 1575 (24) 2100 (23) 1700 (24) 300 (12) 220 (13)

Line 10- Surface --- 215 290 218 -
Bottom 2070 (27) 1675 (28) 2030 (27) 1790 (29) 325 (14) 230 (14)
Line 11- Surface --- 210 305 210 290 ---
Bottom 1990 (26) 1700 (27) 1950 (25) 1700 (28) 1950 (25) 1650 (25)
Line 12- Surface -- 278 205 --- 205
Bottom 1910 (25) 1650 (27) 1950 (25) 1675 (27) 300 (13) 960 (22)

BUREAU OF GEOLOGY

Tabk t, cat...

(i.tce: Chloride contetsa are baied on conductivity-chloride relatlonshipa for each instrument used.

UnderLtned vatus arte laboratory analyses. Numbats in parenthesis indicate approximate depth from

which *plIe was obtained.)

LocatLio North or West bank Canter line South or east bank

April 30 May 21 April 30 Hay 21 April 30 May 21

Line 13- Surface

aBtom

Line L4- Surface

itne 1t- Surface

Dottan

cuttom
tLin 16- Surface

Bottom

Line iL- Surface

Ltnv 10- Surfce
Bottom

Ba:tom
Line LI- Surtace
Line 20- Surface

Lite 21- Surface

aBottom

boccom
Line 2- Surface

face-
faccom.

--

1820 (25)

1%00 ft?)
--

370 (1S)

430 (16)

205

221 (13)

59 (27)

165 (9)

--

160

130 (23)

145 (15)
-*

1650 (26)

412 (19)

170

170 (18)

150

153 (16)

L40

155 (20)

135

440 (28)

130 (11)

130

295 (25)

130

300 (29)

315 (30)

130

315 (30)

265

1875 (27)

255

540 (20)

1250 (20)

212

675 (25)

200

675 (28)

185

625 (27)

610 (24)

160

M (23)

160

M (28)

A78 (29)

145

400 (28)

140

195

1650 (28)

195

640 (21)

155

185 (22)

149

402 (26)

140

505 (29)

135

450 (28)

25 (26)

130

282 (25)

130

302 (29)

130

315 (29)

130

310 (28)

125

270 (13)

255

265 (12)

1065 (19)

510 (23)

205

665 (28)

190

610 (27)

165

580 (24)

525 (26)
..

140

445 (28)

195

235 (14)

195

190 (13)

165

180 (19)

150

355 (24)

520 (29)

140

4 (24)

130

355 (25)

130 (17)

285 (28)

130

130 (13)

130 (14)

388 (27) 305 (28)

INFORMATION CIRCULAR NO. 62 23

Table l, cont...

(Notel Chloride content are based on conductivity-chloride relationships for each instrument used.

Underlined values are laboratory analyses. Numbers in parenthesis indicate approxbiate depth from

which sample was obtained.)

Location North or Weat bank Center line South or east bank

April 30 Hay 21 April 30 May 21 April 30 May 21

Line 25- Surface 130 --- 136 120 ..

Bottom 275 (27) --- 312 (28) 310 (29) 215 (24) -

Line 26- Surface 125 --- 130 115 120 ---

Bottom 230 (28) --- 225 (28) 335 (30) 115 (11) ---

Line 27- Surface 140 --- 145 109 130 ---

Bottom 230 (26) --- 220 (20 318 (26) 210 (25) ---
Line 28- Surface 130 --- 130 105 125 -

Bottom 260 (30) --- 235 (30) 312 (29) 230 (29) ---
Line 29- Surface 120 --- 120 100 120 ---

Bottom 215 (28) --- 8 ()) 300 (27) 115 (14) ---

Line 30- Surface 125 --- 120 100 120 ---

Bottom 115 (13) --- 205 (30) 288 (29) 200 (28)

Line 31- Surface 110 --- 115 100 110 ---

Bottom 200 (28) --- 186 (28) 270 (28) 100 (12) ---

Line 32- Surface 100 --- 100 90 110 ---

Bottom 181 (28) --- 175 (28) 232 (28) 175 (25) ---

Line 33- Surface 115 --- 100 --- 100 ---

Bottom 100 (10) --- 98 (20) -- 100 (18) ---

Line 34- Surface 105 --- 100 --- 100 ---

Bottom 100 (14) --- 132 (29) --- 130 (28) ---

Line 35- Surface 93 --- 100 --- 100

Bottom 100 (22) --- 94 (22) --- 90 (18) ---

Line 36-Surface 110 --- 100 --- 95 ---

Bottom

90 (23)

90 (23)

* 95 (14)

BUREAU OF GEOLOGY

Tabe l,cot.

(Note: Chlartd contents are based on conductivity-chloride relationships for each instrument used.

UndarLtned values are laboratory analyses. Numbers in parenthesis indicate approximate depth from

uhich sIa pl was obtained.)

Locacton North or West bank Center line South or east bank

ApriL 30 May 21 April 30 Hay 21 April 30 Hay 21

Line 17-Surface 95 --- 100 --- 100 .

Bottom 85 (25) --- 86 (26) --- 100 (13)

Lino 38- Surface 95 --- 90 --- 90 ---

Sottom 85 (17) --- 80 (20) -- 8 (11) -
tne 39- Surface 90 --- 85 --- 85

Bottom 85 (17) --- 81 (18) --- 85 (11) -

Line -;- Surface 85 --- 80 --- 80

Bottom 80 (22) --- 80 (22) --- 80 (11) -

Lino t- Surface 85 --- 80 --- 85 --

octtom 80 (23) --- 81 (24) --- 80 (24) ---

Line 42- Surface 85 --- 80 -- 80 ---

toctom 80 (21) --- 80 (22) --- 80 (9) -

Line 43- Surface 85 -- 80 --- 80

Scttom 90 (22) --- 80 (22) --- 80 (24) -

APPROXIMATE CHLORIDE CONTENT, MILLIGRAMS PER LITER

Figure 3. Graph showing the vertical distribution of chloride in water from the center of the river at lines 1 and 4 on
April 30 and May 21, 1968.

Wt

i

S10 -APRIL 30,1968 0 APRIL 30,196

20 .20 -

IL

SO 320 .

April 30 and May 21, 1968.
30 --- ------ 3C --MAY 21---1958-

April 30 and May 21, 1968.

LINE 13 LINE 17 LINE 21 LINE 25
22,200 FEET 30,300 FEET 37,800 FEET 45,400 FEET
FROM DAM FROM DAM FROM DAM FROM DAM
14.2 MILES) (5.8 MILES) (72 MILES) 8.6 MILES)
0 0 0 0

EXPLANATION
-APRIL 30,1968
5 MAY 21,1968 5 5 5

100 J JO

15 15 150 -0
0
m i
I I 0

20 20 20 2- 0
I u

25 5 25 25 25

30 30 30 30
0 IQ00 2000 0 1000 0 1000 0 1000
APPROXIMATE CHLORIDE CONTENT,MILLIGRAMS PER LITER

Figure 5. Graph showing the vertical distribution of chloride in water from the center of the river at lines 13, 17, 21, and
25 on April 30 and May 21, 1968.

BUREAU OF GEOLOGY

As shown in figures 3, 4 and 5, the chloride content of the water was
essentially uniform from the surface to a depth of at least 12 feet. Beneath this
zone of uniform chloride concentration, the chloride content of the water
increased progressively to maximum concentrations at or near the bottom. The
curves for April 30 generally showed a zone of mixing between the upper and
lower zones, where the rate of increase in chloride content per foot of depth was
less than the rate of increase in the lower zone.
Water withdrawn from the upper zone would contain the lowest chloride
concentrations in the contaminated reach, provided that the water at greater.
depths did not migrate upward and mix with the upper water as a result of
pumping. The intake pipes for pumping stations deriving water from the
contaminated reach of the river should be maintained at shallow depths to avoid
pumping water with higher chloride concentrations from the deeper parts of the
river. When large quantities of water are pumped, the resultant high velocities
may require special precautions to avoid this problem. Floating intake structures
which always draw water from near the surface may be required. Shallow intake
canals such as those used at the Lee County water plant and at the Ft. Myers
pumping station may be necessary under certain conditions.
Several other features shown on figures 3, 4 and 5 should be noted. The
chloride content of the water in each successive vertical section decreased with
increased distance from the dam. Comparison of the April 30 and May 21 curves
on figure 3, 4, and 5 shows the effect that discharge from the Franklin Dam,
resulting from local rainfall during the period between the 2 traverses, had on
reducing the chloride concentrations throughout each vertical section of the
river downstream from line 25. It is significant to note that this flushing action
was accomplished at relatively low discharge rates ranging between 80 and 667
cfs (cubic feet per second) measured at the W. P. Franklin Dam (oral commun.,
U. S. Army Corps of Engineers, 1968). Although the average rate of discharge
was about 335 cfs for the 15 days on which discharge occurred between April 30
and May 21, the higher discharge rates probably were more effective in reducing
the chloride concentrations in the deeper sections of the river. The largest
reductions occurred where water velocities were the greatest.
UPSTREAM EXTENT OF SALT-WATER CONTAMINATION
IN APRIL-MAY 1968
The variation in chloride content of river water near the surface and the
bottom, as related to distance upstream from the dam, is shown in figures 6 and
7. The graphs are based on measurements made along the centerline of the river
between lines of sections, using several different map scales. Therefore the
distances given are approximate.

0 2 4 6 8 10 12
DISTANCE, MILES UPSTREAM FROM DAM

14 16 18

Figure 6. Graph showing chloride content of river water at a depth of about 1 foot, as related to distance upstream from the
W. P. Franklin Dam, April 30 and May 21, 1968.

I-
a.
w

| 20(
.J

z
I

J
0

0c
C,.

o

0 2 4 6 8 10 12 14 16 18
DISTANCE, MILES UPSTREAM FROM DAM

Figure 7. Graph showing chloride content of river water near the bottom of the river, as related to distance upstream from the
W. P. Franklin Dam, April 30 and May 21, 1968.

INFORMATION CIRCULAR NO. 62

It is apparent from table 1 and figures 6 and 7 that the chloride content of the
river water decreases with increasing distance upstream from the dam. This
information strongly supports the concept that the major source of
contamination is the repeated injections of salt water through the Franklin Dam
during boat lockages.
Using the U.S. Public Health Service recommended limit of 250 mg/1 of
chloride for drinking water as a standard of reference, it is evident from figure 6
that all of the water near the surface exceeded the limit for a distance of 4.7
miles (near line 14) upstream from the dam on April 30. As shown in table 1,
the maximum chloride content measured near the surface within that reach of
the river was 370 mg/l on that date. By May 21, discharge from the dam had
caused a reduction in chloride content in the river water near the surface to a
maximum of 248 mg/l.
Near the bottom of the channel, water containing more than 250 mg/1 of
chloride extended about 9 miles (near line 26) upstream from the dam on April
30, as shown on figure 7. The maximum chloride concentration measured was
3,500 mg/1, although a value of 3,580 mg/1 was determined from specific
conductance measurements. By May 21 the chloride had been significantly
reduced in the highly contaminated reach of the river. The maximum value
measured at that time was 1,790 mg/l.
An interesting and apparently an unusual feature was determined from
measurements made along the bottom of the river on May 21. This feature,
illustrated on figure 7, concerns the decrease in chloride content downstream
from line 25 (45,400 feet from dam) and the increase in chloride content
upstream as compared to the graph for the April results. Figure 7 and table 1
show that the upstream limit of water containing 250 mg/1 of chloride on May
21 was near line 32, 11.4 miles from the dam, or a movement of 2.5 miles
upstream from the April 30 limit. The upstream movement is substantiated by
measurements made at the Ft. Denaud bridge, near line 34, as follows: May 3,
115 mg/l; May 10, 130 mg/1; May 15, 175 mg/l; and May 22, 210 mg/1.
A logical explanation for the chloride changes upstream and downstream from
line 25 on May 21 is that water entered the river between line 25 and the dam. It
is probable that much of this water entered the river from the Townsend Canal
(near line 25), which drains a large area to the south.
The fact that nearly all of the water discharged at the Franklin Dam between
April 30 and May 21 was from local runoff was verified by a report from the
U.S. Army Corps of Engineers (op. cit.) that no water other than lockage and
leakage was released during that period at the Ortona Lock, 9 miles upstream
from La Belle.
The maximum extent of salt-water contamination is obviously somewhat
greater than indicated by the standard of reference of 250 mg/l of chlorides.
Assuming that contamination from a salt-water source at the dam is indicated by

BUREAU OF GEOLOGY

a higher chloride content for water near the bottom than at the surface, then a
change in this pattern would probably indicate the upstream limit of
contamination. Table 1 shows that most of the measurements made upstream
from line 34 on April 30, for surface and bottom samples, were similar. This
would place the upstream limit of contamination 12.5 miles from the dam on
that day. Although comparable measurements were not made on May 21, the
upstream movement of salt water in the period between the two traverses, as
indicated in table 1 and figure 7, suggests that the upstream limit of
contamination on that day was 13 to 15 miles from the dam.
COMPARISON WITH PREVIOUS RECORDS
Information collected during the river traverses of April 30 and May 21, 1968,
confirm the tentative results presented in earlier investigations. A study of the
chloride content of water in the reach between the Franklin Dam and a point
about 5,600 feet upstream was made by engineers for the City of Fort Myers in
May and July 1965 (Black, Crow, and Eidsness, Inc., 1965). Maximum chloride
concentrations of 2,420 mg/1 were measured on May 31 near the bottom of the
channel at the center of the river, whereas 190 mg/l was the maximum
concentration measured near the surface. Subsequent measurements on July 12
showed that most of the salt water had been flushed from this reach.
On May 19, 1967, a traverse of the river between the dam and Alva was made
by the Geological Survey as part of the cooperative program. The same
procedures and lines of cross sections were used as in the 1968 traverses, so that
direct comparison can be made, as shown in figure 8. The sets of graphs for both
bottom and surface samples show the same general decrease in chloride content
with increased distance from the dam. However, one significant difference
should be noted; the chloride content of water near the surface was consistently
higher on May 19, 1967 than on April 30, 1968, although the water near the
bottom generally contained lower chloride concentrations. Apparently this is the
result of a greater degree of upward mixing caused by wind and wave action,
turbulence created by boat traffic, or other factors which have not been
evaluated. This feature suggests that the forces which control upward mixing are
of considerable importance because they are largely responsible for the increase
in chloride content of water near the surface.
As shown by the upper curves on figure 8, the upstream limit of water near
the surface containing 250 mg/1 of chloride was 5.3 miles from the dam on May
19, 1967. This was 0.6 mile upstream from the position determined from the
measurements made on April 30, 1968. Although the upstream limit of 250 mg/l
of chloride was not determined for water near the bottom of the river in 1967,
the lower curves on figure 8 indicate that the position was similar to that
determined for April 1968.

BUREAU OF GEOLOGY

As shown in figures 3, 4 and 5, the chloride content of the water was
essentially uniform from the surface to a depth of at least 12 feet. Beneath this
zone of uniform chloride concentration, the chloride content of the water
increased progressively to maximum concentrations at or near the bottom. The
curves for April 30 generally showed a zone of mixing between the upper and
lower zones, where the rate of increase in chloride content per foot of depth was
less than the rate of increase in the lower zone.
Water withdrawn from the upper zone would contain the lowest chloride
concentrations in the contaminated reach, provided that the water at greater.
depths did not migrate upward and mix with the upper water as a result of
pumping. The intake pipes for pumping stations deriving water from the
contaminated reach of the river should be maintained at shallow depths to avoid
pumping water with higher chloride concentrations from the deeper parts of the
river. When large quantities of water are pumped, the resultant high velocities
may require special precautions to avoid this problem. Floating intake structures
which always draw water from near the surface may be required. Shallow intake
canals such as those used at the Lee County water plant and at the Ft. Myers
pumping station may be necessary under certain conditions.
Several other features shown on figures 3, 4 and 5 should be noted. The
chloride content of the water in each successive vertical section decreased with
increased distance from the dam. Comparison of the April 30 and May 21 curves
on figure 3, 4, and 5 shows the effect that discharge from the Franklin Dam,
resulting from local rainfall during the period between the 2 traverses, had on
reducing the chloride concentrations throughout each vertical section of the
river downstream from line 25. It is significant to note that this flushing action
was accomplished at relatively low discharge rates ranging between 80 and 667
cfs (cubic feet per second) measured at the W. P. Franklin Dam (oral commun.,
U. S. Army Corps of Engineers, 1968). Although the average rate of discharge
was about 335 cfs for the 15 days on which discharge occurred between April 30
and May 21, the higher discharge rates probably were more effective in reducing
the chloride concentrations in the deeper sections of the river. The largest
reductions occurred where water velocities were the greatest.
UPSTREAM EXTENT OF SALT-WATER CONTAMINATION
IN APRIL-MAY 1968
The variation in chloride content of river water near the surface and the
bottom, as related to distance upstream from the dam, is shown in figures 6 and
7. The graphs are based on measurements made along the centerline of the river
between lines of sections, using several different map scales. Therefore the
distances given are approximate.

INFORMATION CIRCULAR NO. 62 33

500

-. .MAY 19, 1967

400

S APRIL 30,1968

300

a: ONE FOOT BELOW SURFACE
w 200IIIII

a-

cn 3500

_J
S 3000-
S\ APRIL 30,1968
Z
w
I-
z

8 2000 -,

S2000 \ I \

I 2 3 4 5 6

Figure 8. Graphs showing chloride content of river water on May 19, 1967 and April 30, 1968,
as related to distance upstream from the W.P. Franklin Dam.

BUREAU OF GEOLOGY

Several other salinity surveys of the river were made in 1967. One of these
was conducted by the Florida State Board of Health (written commun., T. B.
Miller, 1967) on June 1, 1967 between State Highway 31 (about 5 miles
downstream from the W. P. Franklin Dam) and the lock at Moorehaven (near
Lake Okeechobee). The results showed that the chloride content of water in the
tidal reach of the river ranged from 11,000 to 14,000 mg/l, with about 12,000
mg/1 determined near the base of the dam. Chloride values less than 100 mg/l
were measured upstream from La Belle. The second survey was made by the
consulting firm of Black, Crow, and Eidsness, Inc., (written commun.) on June
2, 1967 for the same reach of the river as that measured in 1965. The results
obtained showed significantly higher concentrations of chlorides at all stations as
compared with the 1965 measurements. A maximum chloride content of 3,240
mg/l was determined for water near the bottom, and 527 mg/l measured near the
surface-
The results of all three surveys conducted in May-June 1967 showed good
general agreement where comparable data were available. The data for June
showed higher chloride concentration in the deeper parts of the river channel,
indicating continued upstream movement of salt water from May 19 to June 2,
1967.
Numerous other chloride measurements have been made for water in the
Caloosahatchee River between 1966 and 1968. Selected measurements are
summarized in table 2. Samples for chloride analyses have been collected
routinely at the site of conductivity recorder C-1 (fig. 2), about 450 feet
upstream from the dam, since March 1966. Measurements made at that location
give early warning of changes in chloride content in the fresh-water pool above
the dam. From the available records, it is concluded that chloride values
exceeding about 80 mg/1 are evidence of salt-water contamination. It is noted
from table 2 that values exceeding 80 mg/1 were measured over 2 extended
periods of record since March 1966. The first began in late November 1966 and
ended in late June 1967, a period of about 7 months. The second began in
mid-December 1967 and ended in early June 1968, a period of about 5
months. These periods of increased chloride concentrations generally coincide
with the periods of low flow in the Caloosahatchee River. Other measurements
given in table 2 show the progressive increase in chloride content of water at
points upstream from the dam.
As discharge from the dam increases following rainfall in the basin, or as a
result of regulatory releases of water from Lake Okeechobee, the chloride
content of water in the affected reach decreases to values as low as 30 mg/l.
Although detailed surveys have not been made during high-discharge periods, the
available evidence suggests that all of the contaminated reach above the dam was
flushed during the periods of high discharge. In fact, sustained high discharge can
move the salt water a significant distance downstream from the dam. For
example, measurements made in the tidal reach of the river on July 22, 1966

Table 2. Miscellaneous measurements of chloride concentrations (mg/1) in the Caloosahatchee River upstream from the W. P. Franklin Dam.

Dates 1968
Locatiun 1-4 1-11 1-18 1-25 2-1 2-7 2-14 2-21 3-5 3-11 3-22 4-12 4-19 4-26 5-3 5-10 5-15 5-22 5-29 6-5
Recorder C-1
Surface 90 160 155 165 165 210 245 245 345 265 245 310 420 385 410 440 355 225 130 55

Bottom 100 155 175 175 190 560 485 330 350 275 1850 540 750 1700 410 550 450 275 140 60

County intake

Surface 180 160 195 240 220 230 300 385 370 390 440 330 125

Bottom 625 910 1350 1070 1625 2150 2600 2150 1550 1450 1050 130

Alva Bridge

Surface 95 185 150 190 230 235 225 260 150 145 95 55

Bottom 170 220 200 585 405 700 665 855 380 325 95 50

Ft. Denaud Bridge

Surface 95 120 85 100 65 45

Bottom 115 130 175 210 65 45

b Selected chloride measurements at Recorder C-1. 1966-67 7
196 1967

Surface .- -.. .- 312 610 215 110

Bottom 73 65 67 63 64 51 47 30 38 126 150 120 205 127 122 160 235 388 1350 720 220 58 33 40 70 105 115

3-15 4-6 4-27 6-1 7-1 7-29 8-16 9-30 10-28 11-25 12-9 12-30 1-24 2-1 3-4 3-17 4-1 4-25 5-2 5-31 6-13 6-26 8-31 10-2 11-27 12-11 12-21

BUREAU OF GEOLOGY

a higher chloride content for water near the bottom than at the surface, then a
change in this pattern would probably indicate the upstream limit of
contamination. Table 1 shows that most of the measurements made upstream
from line 34 on April 30, for surface and bottom samples, were similar. This
would place the upstream limit of contamination 12.5 miles from the dam on
that day. Although comparable measurements were not made on May 21, the
upstream movement of salt water in the period between the two traverses, as
indicated in table 1 and figure 7, suggests that the upstream limit of
contamination on that day was 13 to 15 miles from the dam.
COMPARISON WITH PREVIOUS RECORDS
Information collected during the river traverses of April 30 and May 21, 1968,
confirm the tentative results presented in earlier investigations. A study of the
chloride content of water in the reach between the Franklin Dam and a point
about 5,600 feet upstream was made by engineers for the City of Fort Myers in
May and July 1965 (Black, Crow, and Eidsness, Inc., 1965). Maximum chloride
concentrations of 2,420 mg/1 were measured on May 31 near the bottom of the
channel at the center of the river, whereas 190 mg/l was the maximum
concentration measured near the surface. Subsequent measurements on July 12
showed that most of the salt water had been flushed from this reach.
On May 19, 1967, a traverse of the river between the dam and Alva was made
by the Geological Survey as part of the cooperative program. The same
procedures and lines of cross sections were used as in the 1968 traverses, so that
direct comparison can be made, as shown in figure 8. The sets of graphs for both
bottom and surface samples show the same general decrease in chloride content
with increased distance from the dam. However, one significant difference
should be noted; the chloride content of water near the surface was consistently
higher on May 19, 1967 than on April 30, 1968, although the water near the
bottom generally contained lower chloride concentrations. Apparently this is the
result of a greater degree of upward mixing caused by wind and wave action,
turbulence created by boat traffic, or other factors which have not been
evaluated. This feature suggests that the forces which control upward mixing are
of considerable importance because they are largely responsible for the increase
in chloride content of water near the surface.
As shown by the upper curves on figure 8, the upstream limit of water near
the surface containing 250 mg/1 of chloride was 5.3 miles from the dam on May
19, 1967. This was 0.6 mile upstream from the position determined from the
measurements made on April 30, 1968. Although the upstream limit of 250 mg/l
of chloride was not determined for water near the bottom of the river in 1967,
the lower curves on figure 8 indicate that the position was similar to that
determined for April 1968.

BUREAU OF GEOLOGY

after an extended period of high discharge, showed that water containing 50-60
mg/1 of chloride was located about 23 miles downstream from the dam at the
surface and at the bottom; about 4 miles farther downstream (27 miles from the
dam) chloride values of 4,000 mg/l at the surface and 10,000 mg/l at the bottom
were determined from specific conductance measurements. However, following
the reduction in discharge from the river on November 9, 1966, evidence of
salt-water contamination upstream from the dam was recorded at C-1 on
November 24.
CONCLUSIONS
Previous studies and data included in this report have shown that the intrusion
of salt water from the tidal reach of the Caloosahatchee River periodically
results in a substantial increase in chloride concentrations in the fresh-water
reach. of the river for many miles upstream from the W. P. Franklin Dam. The
major point of entry has been identified as the boat-lock chamber where salt
water enters during the opening of the downstream lock gates and moves
upstream with the opening of the upstream lock gates. The available evidence
suggests that chloride contamination from sources other than through the lock
chamber can be only minor factors contributing to the chloride contamination.
The maximum extent of contamination upstream from the dam and the
ultimate effect of mixing of this water throughout the vertical section of the
river is related to a number of independent variables. Using 250 mg/l of chlorides
as a standard of reference, the upstream limit of water near the surface
containing this concentration was 5.3 miles from the dam on May 19, 1967 and
4.7 miles on April 30, 1968. The similarity of these data would lead to the
assumption that the upstream limit of this degree of contamination was
reasonably well defined. However, the validity of this assumption may be subject
to serious question if all factors related to the problem are considered. Although
a discussion of these factors is beyond the scope of this report, the following
comments based on present knowledge appear warranted:
I. The maximum upstream extent of contamination is primarily related to
the number of injections of salt water upstream and to the volume of water
discharged downstream. Both factors are time related. Therefore, effective
control measures should include methods for (1) reducing the number of
injections of salt water, (2) flushing of salt water from the river, (3) a
combination of both.
2- The forces which cause upward mixing of salt water and increase in
chloride content near the surface include wind and wave action and the
turbulence created by boat traffic. Fast-moving boats of medium draft and
slow-moving boats of deep draft cause large oscillations within the relatively
narrow river channel. Further study of mixing phenomena will be required if
control measures are to be effective.

INFORMATION CIRCULAR NO. 62

In conclusion, it may be stated that the numerous proposed solutions to the
problem of water quality embody either the concept of "total control" or
"partial control." Proposals within the total control concept range from the
construction of tidal dams to the creation of upstream barriers to limit salt-water
movement. Some of these proposals merit consideration as a long-term solution
but they require extensive engineering studies prior to construction.
Within the partial-control concept, effective methods of reducing
contamination are immediately available, provided they are correctly applied
when needed. Although the methods cannot be outlined in detail based on
present information, the following procedures may be of considerable benefit in
controlling contamination:
1. At the first indication of the upstream movement of salt water, as
monitored by gaging equipment, reduce the number of openings of the upstream
lock gates by placing lock operations on a time schedule.
2. Flush lock chamber following downstream lockage of boats when possible.
3. Pending further study, control speed of large craft in contaminated reach
of river.
4. If an excessive increase in chloride content occurs, release sufficient
quantities of water from storage for flushing contaminated reach. The flushing
effects should be carefully evaluated to determine accurately the quantity of
water required.
These procedures can be correctly applied only by the establishment of
suitable monitoring stations which would be operated continuously during the
low-flow period.
The probable large-scale increase in water requirements for municipal,
industrial, and irrigation uses over the next several decades, and the probable
increase in boat traffic moving through this section of the river indicate the need
for an early permanent solution to the contamination problem. The solution
may also require a hydrologic investigation of the river basin between the
Franklin Dam and the Moorehaven Lock to collect and evaluate detailed
information on the quantity and quality of water available from small streams
which enter the river during low-flow periods, and from shallow aquifers.

INFORMATION CIRCULAR NO. 62

REFERENCES

Black, Crow, and Eidsness
1965 Engineering Report, Water Supply Studies, City of Fort Myers, Project No.
295-65-R, p. 5-1 to 5-15.
Boggess, D. H.
1968 A test of flushing procedures to control salt-water intrusion at the W. P.
Franklin Dam, near Fort Myers, Fla.: U. S. Geol. Survey open-file report, 27
p., 7 figs.
U. S. Public Health Service
1962 Public Health Service drinking water standards, 1962: Public Health Service
Pub. 956, 61 p.

FLRD GEOLOSk ( IC SUfRiW

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[year of publication as printed] Florida Geological Survey [source text]

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	Title Page
	Part I: Table of Contents
	Part II: Table of Contents
	Introduction
	Proposed testing procedures
	Results of test procedure...
	Summary and conclusions
	Reference
	Abstract and introduction
	Data collection procedures and...
	Upstream extent of salt-water...
	Comparison with previous recor...
	Conclusions
	References

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