UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY
SCIENCE AND ECOSYSTEM SUPPORT DIVISION
REGION 4

wEPA	

THOMAS R. CAVINDER, P.E.

980 COLLEGE STATION RD.

ATHENS, GA 30605-2720	(706) 355-8719

CAVINDER.TOM@EPAMAIL.EPA.GOV	FAX (706) 355-8726

WATER QUALITY AND
SANITARY SURVEY
SANIBEL ISLAND, FLORIDA
JUNE, 1977

ENVIRONMENTAL PROTECTION AGENCY
SURVEILLANCE AND ANALYSIS DIVISION
ATHENS, GEORGIA

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77-

WATER QUALITY AND
SANITARY SURVEY
SANIBEL ISLAND, FLORIDA
JUNE, 1977





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TABLE OF CONTENTS

TITLE	PAGE NO.

INTRODUCTION 		1

SUMMARY		2

RECOMMENDATIONS		3

BACKGROUND 		3

STUDY AREA		5

STUDY RESULTS		6

Groundwater Hydrology		6

Groundwater Chemical Quality 		7

Groundwater Bacterial Quality	10

West Rocks Lake Chemical and Physical Quality	12

West Rocks Lake Bacterial Quality		

Estuarine Water Chemical and Physical Quality	14

Estuarine Water Bacterial Quality		

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LIST OF FIGURES

PAGE NO.

1.	Study Area		19

2.	Study Sites		20

3.	West Rock Subdivision		21

4.	Unit 27 West Rocks Subdivision		22

5.	Unit 29 West Rocks Subdivision		23

6.	Study Area Finger Canals		24

7.	Groundwater Levels 		25

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LIST OF TABLES

PAGE NO.

A.	Distance of Travel of Fecal Microorganisms		5

B.	Time of Survival of Fecal Bacteria		5

1.	Hydrographic Data Summary 		8

2.	Well Water Quality Data Summary		9

3.	Groundwater System - Fecal Coliform 		11

A.	West Rocks Lake Chemical Data		12

5.	West Rocks Lake - Fecal Coliform		14

6.	Tidal Canals - Chemical Data		15

7.	Tidal Canals - DST		16

8.	Tidal Canals - Fecal Coliform 		18

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INTRODUCTION

The City of Sanibel, Florida requested the U.S. Environmental Protection
Agency to assess the effect of septic tank/drainfields on ground and surface
waters of the Sanibel environs.

The purpose of these assessments is to provide a technical foundation to
the City so that a viable ordinance with regard to the use of septic tank/
drainfield systems could be developed.

Thomas M. Missimer and Associates Inc., under contract to the City, completed
in December 1976, an investigation of the use of septic tanks on the island. Thei
study produced a strong data base but lacked ample bacteriological, dye tracer
and near shore estuarine water quality investigations.

The US-EPA conducted water quality investigations on Sanibel Island during
the period of June 6-15, 1977. The studies were designed to utilize the well
network and septic tank/drainfield systems employed by Missimer and Associates,
Inc., and to supplement the existing data base by performing bacteriological,
dye tracer and near shore estuarine water quality investigations. Objectives
of these studies were:

•	To determine the effect of leachates on the water table aquifer
by conducting water quality investigations of the water table
aquifer upgradient and downgradient from septic tank/drainfleld
systems;

•	To determine the effect of leachates on "real estate" lakes by
conducting water quality investigations of lakes (interior barrow
pits) in the vicinity of septic tank/drainfield systems;

•	To determine the residence times of the leachates in the soil/water
systems by tracing by means of dye, the movement of domestic wastes
through the septic tank/drainfield system to the aquifer and to

1

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surface waters, and
» To determine the effect of leachates on ambient estuarine waters
by conducting water quality studies in the estuarine system in
the vicinity of septic tank/drainfield systems.

SUMMARY

1.	Groundwater levels and gradients were atypical during the study period.
Groundwater elevations experienced were 4.4 to 6.0 feet below the ground
surface. During September 19 76, the groundwater elevations were 2 feet
higher resulting in less than 4 feet between the ground surface and the
groundwater level.

2.	Leachate traced with dye was not detected in any of the downgradient
well points or surface waters during the study period.

3.	Nitrogen and phosphorus concentrations increased up to 39 and 42 times
respectively, between upgradient and downgradient well points in the
septic tank drainfields.

4.	Near shore phosphorus levels in the vicinity of septic tank systems
were 10 times those of the interior of West Rocks Lake. The dense
population of aquatic vegetation in West Rocks Lake is likely being
perpetuated by nutrient enrichment via septic tank leachates.

5.	Fecal coliforin levels exceeding bathing waters criteria were experienced
in West Rocks Lake.

6.	No Salmonella organisms were isolated at any station sampled.

7.	Dissolved oxygen levels in the tidal finger fill canals revealed many
(6 out of 9 stations) violations of state standards at depths exceeding
5 to 7 feet mean low water.

8.	Fecal coliform levels in the tidal canals during this survey were quite
low (2 or less per 100 ml).

2

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9. High fecal densities were found downgradient from drainfields during

low groundwater drainage periods where no leachate movement was observed
during dye tracer studies. These results indicate that fecal coliforms
may survive for long periods of time in groundwater systems.

RECOMMENDATIONS

1.	Data from the real estate lake studied reveal that septic tank drainfields
should not be positioned along its shoreline. Even during the low ground-
water levels experienced during this study the aggrevation to this water
body is replete in respect to bacteriological and chemical data.

2.	Further studies using the existing well points at West Rocks Lake should
be conducted during high groundwater levels to enumerate fecal coliform

densities (MPN tube method).

3.	Efforts should be made via local, state and federal agencies to expedite
ordinances and facility planning to replace septic tank drainfield systems
with adequate area wide conventional wastewater treatment.

4.	Until such time as conventional wastewater treatment is provided, routine
monitoring for bacteriological parameters should be performed in the real
estate lakes if they are to be used for recreational purposes.

BACKGROUND

Prior to discussing the field study, three excerpts of work of others will
be cited. These references serve as a guide to the scope of the problem of
employing septic tank/drainfields in high water table areas and in proximity

to surface water bodies.

1. Hydrology for Urban Land Planning - A Guidebook on the Kydrologic

Effects of Urban Land Use, Geological Survey Circular 554, states:

"... observations indicate that, for soil cleansing to be effective,

contaminated water must move through unsaturated soil at least 100

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feet. Owing to the gentle gradient of the water table near perennial
streams and the fact that seepage water moves vertically as well as
toward a nearby channel, it would seem prudent that no septic tank
should be as close to a channel as about 300 feet, if protection of
the stream water quality is to be achieved. The distance should
probably be greater from a perennial than from an ephemeral channel.
(An emphemeral stream is one which contains flowing water only in
storm periods.) In general, it might be advisable to have no source
of pollution such as a seepage field closer than 300 feet to a
channel or watercourse."

"Even this minimum setback does not prevent the dissolved materials
(nitrates, phosphates, chlorides) from enriching the stream water
and thus potentially encouraging the proliferation. >of algae and other-
wise creating a biotic imbalance."

2.	The Manual of Septic Tank Practice, U.S. Department of Health, Education
and Welfare, 1957, recommends "the maximum seasonal elevation of ground-
water table should be at least four feet below the bottom of the trench
or seepage pit."

3.	Septic Tanks and the Environment, Illinois Institute for Environmental
Quality, Chicago, Illinois, 1971 states:

"Tables A and B summarize the available data on time and the distance
of travel of fecal bacteria in the septic system and soil absorption
field. The results of some of the early investigations seem extreme,
particularly in view of the rather imprecise identification techniques
available in the 1930's. The data indicates that fecal organisms may
survive for quite long periods in the septic tank and soil, during
which time they may be transported by groundwater movement over relative!

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long distances. As the bacteria concentration in septic tank
effluent may be quite high, as many as 93 million coliforms per
100 militer being reported by Polkowski and Boyle (1970), large
quantities of fecal organisms are carried each day into the soil

absorption field."

TABLE A. DISTANCE OF TRAVEL OF FECAL MICROORGANISMS

Type of Organism

Distance Transported, ft.

Vertical	Horizontal	Reference

E. coli
E. coli
E. coli
E. coli

Coliform bacteria
Coliform bacteria
Coliform bacteria
Coliform bacteria



232

Warrick & Muegee, 1930

10-30



Mom & Schaafsma, 1933



80

Caldwall, 1937



400

Dappert, 1932



10-400

Miller, et al, 1957

2-3



Malia & Snellgrove, 1958



180

Randall, 1970

150



Hickey & Duncan, 1966

TATtT.K B. TIME OF SURVIVAL OF FECAL COLIFORM

Type of Organism

Salmonella typhosa
Salmonella typhosa
Salmonella typhosa
Salmonella typhosa
E. coli
E. coli

Coliform bacteria
Coliform bacteria

Survival Time
Septic Tank 	Soil

27 days
24 days

24-41 days

2	years

3	months
4-7 days

Reference

Caldwell, 1933
Warrick & Muegge, 1930
Beard, 1938
Green & Beard, 1938
Warrick & Muegge, 1930
Mom & Schaafsma, 1933
Mail & Snellgrove, 1958
Surbrahamanyan & Bhaskaran
1950

STUDY AREA

Sanibel Island is a barrier island located on the Gulf of Mexico near Ft.
Myers, Florida. The island form, the southern boundry of Pine Island Sound
(Figure 1) and features some of the most beautiful beaches in the State of
Florida. Northeastern portions of the island have been developed into finger
canal housing areas while the interior areas of the island have been developed
around "real estate lakes." These lakes are in reality barrow pits, developed

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to obtain fill for localized housing units. The Gulf beaches are predominately
developed into condominiums, motels and vacation cottages.

The near shore estuarine areas feature high use in the categories of day
sailing, recreational boating and fishing.

STUDY RESULTS

Groundwater Hydrology

The groundwater hydrology study was broken into two facets; (1) groundwater,

ground surface and tide water elevation and (2) dye tracing of leachates through

the groundwater system. The first task was accomplished throughout the study

period by standard leveling techniques and tape downs via well points. Leachate

tracing was conducted by means of well points and automatic samplers positioned

upgradient, downgradient and at surface water bodies in the vicinity of drain-

field systems.

Four drainfield systems were used for the study (Figure 2). Two of the
systems located in the West Rocks subdivision were those used by Missimer and
Associates and had well point systems positioned in the vicinity of the drain-
fields (Figures 3, 4 and 5). The remaining two septic tank/drainfield areas
studied were in a small finger fill canal devlopment at the extreme northern

, . /TMrnirP 6}. Well points were not installed at these
end of Dixie Beach Blvd. (Figure o;.	f

latter two locations.

One gallon of Fhodamine VT dye w»s Injected Into the septic tank et each

of the four locations via the house drains. Automatic samplers were then employed

at downgradient well points/surface waters to collect the traced leachate at hourly

intervals as it traveled through the groundwater system. A mlcrofluorometer was

used to detect the presence of dye in the collected samples.

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Results of the hydrogeologic study are summarized in Table 1. As seen
from this table the ground surface elevations ranged from 4.4 to 6.0 feet and
the groundwater table or mean tide level was 4.4 to 6.0 feet below the ground
surface. Assuming a distance of 2 feet from the gound surface to the draintile
invert results in a distance from the invert to the water table 2.4-4.0 feet.

Due to the minimal amount of rainfall experienced in the spring and early
summer of this year the groundwater levels were well below normal levels. Figure
7 depicts the groundwater levels experienced by Missimer and Associates in Sept.
October, 1976 at well system W-l, W-2, W-3, W-4, W-6 and W-7 in the West Rocks
Subdivision. Note that the groundwater level during the EPA survey of June 6-15,
1977 was nearly two feet below that of September 7, 1976. If a two foot rise
in the groundwater level is applied to the data in Table 1 the distance from the
ground surface to groundwater level would range from 4.0 to 3.4 feet (not including
stations W-ll and W-12 in the finger canal area). Allowing two feet from ground
surface to the drain tile invert would result in two feet or less between the
invert and the groundwater table. A minimum of 4.0 feet is recommended (see

Background Section).

During the study period dye was not detected at any of the sites. With

the atypical groundwater levels experienced the lack of leachate movement during
this short time period was not surprising.

Groundwater Chemical Quality

collected via automatic samplers at each of the
Groundwater samples were coxxcu

, ,t o w w-4 W-6. W-9 and W-10. Automatic samplers
well points, i.e., W-l, W-2, W-J, w «~, w ,

, 4 j ««. i-he surface water bodies adjacent to the well networks,
were also positioned at tne suric*

i.e., stations W-7, W-ll and W-12. Samples were collected hourly and composited
daily for three consecutive 24-hour periods.

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STATION

GROUND

SURFACE

ELEVATION

TABLE 1
HYDROGRAPHIC DATA SUMMARY
SANIBEL ISLAND
JUNE 1976

WATER	TIDE	LAKE

TABLE	WATER	WATER

ELEVATION ELEVATION ELEVATION

DISTANCE FROM
GROUND
SURFACE

TO WATER DISTANCE FROM
TABLE OR WATER TABLE
MEAN TIDE TO LAKE WATER
ELEVATION ELEVATION

W-l

W-2

W-3

W-4

W-6

W-7

W-9

W-IO

W-ll

W-12

W-13

5.33 ft.

5.53

5.96

5.73

5.53

5.49
4.43
5.0
5.0

0.04 ft.

0.15

0.02

0.12

0.07

0.10
0.12

- ft.

0.05 ft.
-0.05
-0.05
-0.05
-0.05
-0.05
-0.05
-0.05

Mean = 0.65
Range = 1.75

5.37 ft.

5.68

5.98

5.85

5.60

5.59
4.55
4.35
4.35

0.01 ft.
-0.10
0.03
-0.07
-0.02

-0.05
-0.07

-0.05

Note: All elevations referenced to sea level datum

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Results of the well system sampling is summarized in Table 2. Well system
W~1 thru W-7 (W-7 is in the lake) provides a comparison of groundwater quality
uPgradient, and downgradient from the drainfield and from surface water down-
gradient from the drainfield. By using upgradient station W-l and comparing
its water quality parameters to those of downgradient stations W-3, w-4 and
the infusion of nutrients into the groundwater system via the drainfield
is readily evident. Nitrogen and phosphorus concentrations increased 11 to 39
fold and 28 to 42 fold, resp.ctlvely,	upgr.dl.nt Co downgradient stations,

i.e., station W-l to stations w-3, w-4 and W-6. Total organic carbon Increases

(TOC) were much less dynamic with an increase of 1.8 to 2.4 fold Note that
station W-7 revealed a phosphorus increase of 4.3 fold over station W-l. Further
comparisons will be made in this report between station W-7 and four stations
(L-l, L-2, L-3 and L-4) located in the interior of West Rocks Lake (Figure 3)

Stations W-9 thru W-12 revealed less dynamic increases above background levels
but generally followed the trend of nutrient enrichment downgradient from the
drainfields.

TABLE 2

WELL WATER QUALITY DATA SUMMARY
SANIBEL ISLAND
JUNE 1977

AVG. % OF AVG. % OF AVG	'/ r>v

STATION T-P	BACKGROUND T-N	BACKGROUND TOC TUfTOmmp

fJ-J	0.09 mg/1

W-2	0.14

,^3	2.6

W-4	2.9

TW~6	3.8

tW~7	0.39

0.04

W-10 0>13
J*"11	0.09

7~12	0.07

Note: *0 Background for stations W-2 thru W-10 based upon upgradient well W-l.

• Background for stations W-ll and W-12 based upon water quality stations
E-l thru E-5 located in the adjacent finger fill canal system.

Avg. T-P, T-N and TOC values for these stations were 0.057, 0.24
and 5.4 mg/1, respectively.	'

*

0.98 mg/1

*

4.0 mg/1



156

11.37

1160

6.0

150

2889

39.01

3981

9.6

240

3222

11.0

1122

7.7

193

4222

21.3

2173

7.5

188

433

1.12

114

22.2

555

44

0.93

95

8.7

218

144

1.51

154

6.4

160

158

0.40

167

4.6

85

123

0.33

. 138

4.0

74

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Groundwater Bacterial Quality

Samples for fecal coliform bacteria analyses were collected twice per
day for four days from stations W-l thru W-12. Station W-13 was sampled four
times during the study. At the well stations (W-l, 2, 3, 4, 6, 9 and 10) samples
were collected by a small pump and sterilized tubing. Samples from the open
water stations (W-7, 11, 12 and 13), adjacent to the drainfields, were taken
directly into sterile bottles.

In addition, swabs were installed at stations W-7, W-ll and W-12 to detect
the presence of members of the bacterial genus, salmonella.

Results of the groundwater system bacteriological analyses are given in Table
3. As a criterion to evaluate the above data the following paragraphs have been
taken from a pre-publication copy of "Quality Criteria for Water" by the U.S.
Environmental Protection Agency.

"Bathing waters - Based on a minimum of not less than five samples taken
over a 30-day period, the fecal coliform bacterial level should not exceed
a log mean of 200 per 100 ml, nor should more than 10 percent of the total
samples taken during any 30 day period exceed 400 per 100 ml."

"Shellfish harvesting waters - not to exceed a median fecal coliform
bacterial concnetration of 14 mpn per 100 ml with no more than 10 perceat
of samples exceeding 43 mpn per 100 ml for the taking of shellfish."

Obviously bathing water standards are not germaine to groundwater wells
aor are shellfish standards applicable in freshwater lakes but the standards
io provide a basis for comparison purposes. Near shore surface water stations
*-7, W-ll, W-12 and W-13 did not exceed the log mean fecal coliform bacteria of
200 per 100 ml for bathing waters. However, station W-7 did exceed the bathing
"aters criteria in reppect to 10 percent of the samples did exceed 400 per 100 ml.

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TABLE 3
GROUNDWATER SYSTEM
FECAL COLIFORM BACTERIA DENSITIES
SANIBEL ISLAND, FLORIDA

6/6/77 6/7/77 6/8/77 6/9/77 6/10/77 6/11/77 LOGARITHMIC ARITHMATIC
STATION	PM	AM PM	AM PM	AM PM	AM PM AM	 MEAN	MEAN

W-l

< 2

<2

<2

< 2

< 2

< 2

< 2

<2

<2

<2

<2

W-2



< 2

<2

< 2

< 2

< 2

< 2

< 2

<2

<2

<2

W-3



<2

< 2

< 2

<2

< 2

< 2

< 2

<2

<2

<2

W-4



< 2

< 2

< 2

< 2

< 2

< 2

< 2

<2

<2

<2

W-6



< 2

33

79

790

79

630

13

330

74

246

Vf-7

23

1300

230

490

79

23

13

49

330

103

282

W-9



< 2

< 2

< 2

<2

< 2

< 2

< 2

< 2

< 2

< 2

W-10



<2

< 2

490 >

2400

1300

230

490

490

155

676

W-ll





< 2

2

2

5

< 2

<2

2

2

2

W-12





2

2

8

< 2

< 2

< 2

< 2

2

3

W-13













17

49

64 11

28

35

(1) 5 Tube mpn - Fecal Coliforms/100 ml.

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Stations W-7 and W-13 on West Rocks Lake both exceed shellfish fecal coliform
bacteria criteria. Stations W-ll and W-12 located on the finger canal system

maintained shellfish harvesting criteria.

In general the fecal coliform bacteria concentrations were relatively low
during this dry period. The near shore coliform densities of West Rock Lake
follow the same pattern as the nutrient responses described earlier, that is,
both indicate infusion of leachates into the near shore surface waters of West

Rock Lake.

No salmonella colonies were Isolated at the near shore stations, I.e.,

stations W-7, W-ll and W-12.

West Rock T.ake Chemical and Physical Quality

Mid-depth quality samples were collected twice daily tor two days from the

interior of West Rocks Lake. Figure 3 depicts the four sampling stations (L-l,

1-2, L-3 and L-4). Results of the chemical analyses are given in Table 4.

TABLE 4
CHEMICAL DATA SUMMARY
WEST ROCKS LAKE
SANIBEL ISLAND

Ration no9-n(h	nh3	tkn .

<0.01	0.01	0.80

"ln- <0.01	0.01	0.70

ean <0.01	0.01	0.75

1^2

<0.01	0.01	0.85

M^n' <0.01	0.01	0.80

an <0.01	0.01	0.82

U3

<0.01	0.01	0.85

<0,01	°'01	°'80

an <0.01	0.01	0.82

L-4

<0.01	0.01	1.10

ttea <0.01	0.01	0.83

n <0.01	0.01	0.96

Lake Mean <0.01	0.01	0.84









SALINITY

TEMP

T-P

T0C

T-N

DO

0/00

oc

0.06
0.04
0.05

19.0
8.3
13.6

0.81
0.71
0.76

8.0
4.5
5.8

3.9
3.9
3.9

31

29

30

0.04
0.04
0.04

20.0
19.3
19.6

0.86
0.81
0.83

7.7

4.6

5.7

3.9
3.9
3.9

31

29

30

0.04
0.03
0.03

20.0
19..7
19.8

0.86
0.81
0.83

10.0
5.1
7.0

3.9
3.9
3.9

31

29

30

0.04
0.03
0.03

20.0

19.7

19.8

1.11
0.84
0.97

8.1
5.6
6.4

3.9
3.9
3.9

31

29

30

0.04

18.2

0.85

6.2

3.9

30

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West Rocks Lake has a dense population of rooted aquatic vegetation whose
effect is readily apparent in the dissolved oxygen (DO) data. In-situ measurements
of DO were performed during each of the water quality sampling periods and were
conducted during the photo period of 8 a.m. to 4 p.m. Dissolved oxygen saturation
for the temperature and salinity experienced is 7.5 mg/1. As seen from Table 4,
all stations revealed maximum DO levels well above the saturation value. Missimer
and Associates conducted diel studies in the lake. Their data readily depicts
the diel pattern of DO fluctuations due to metabolic respiration and photosynthesis.

Water column nutrient concentrations reveal an abundance of nitrogen available
for metabolic demands but indicate a limitation in regard to phosphorus. One
~nly needs to focus on stations W-6 and W-7 (Table 2) which are respectively just
shoreward and at the waters edge near one of the studied septic tank/drainfield
systems in West Rocks Subdivision. Phosphorus concentrations at these stations
rere 3.8 and 0.39 mg/1, respectively. Station W-7 (at the waters edge) reveals
i phosphorus level 10 times that of the mean lake concentration (0.09). Nitrogen

values follow the same pattern.

In summary the lake is densely populated with aquatic vegetation and this

:ondltion is apparently being aggrevated by the infusion of nutrient laden

roundwater In the vicinity of septic tank/dralnfield systems.

est Rocks Lake BaC"",'al Quallt:y

Bacteriological samples were collected In conjunction with the water quality

amples. Collection was accomplished by means of sterile bottles at a sampling

epth of one foot below the water surface. Salmonella swabs were placed at

tations L-l, 1-3 and L-4. Results of the bacteriological analyses are given

i Table 5.

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PM

AM

PM

AM

PM

AM

MEAN

MEAN

33

70

22

23

28

70

36

41

33

41

33

79

49

13

36

41

33

49

33

49

49

23

38

39

40

23

23

23

109

13

30

39

TABLE 5
WEST ROCKS LAKE
FECAL COLIFORM BACTERIA DENSITIES
SANIBEL ISLAND, FLORIDA

6/6	6/7	6/8	6/9 LOGARITHMIC ARITHMATIC

STATION AM

L-l
L-2
L-3
L-4

(1) - 5 Tube rapn - Fecal coliforms/100 ml.

Fecal coliforms were well within bathing water standards at the time of
this survey. During periods of high groundwater levels the effect of septic
tank leachate would probably be more pronounced in the lake as compared to just

the near shore area in this survey.

No Salmonella colonies were isolated in the lake stations.

Estuarine Water Chemical and Physical Quality

Studies were conducted to measure the water quality conditions of the inland

tidal finger fill canals. During the period of 6/11-13, water quality samples

were collected from mid-depth at eleven can&l stations (Figure 6). In addition

to the water chemical sampling, in-situ measurements were taken at each station

,	fn one foot from the bottom at one foot intervals,

from a depth of one foot to one iouu

Results of these sampling programs are given in Tables 6 and 7.

Nutrient levels in the tidal canal stations E-l thru E-5 and E-7 thru E-ll

than those of background station E-6. The
reveal no significant differences tnan

, (at stations E-l, E-2 and E-3) that NH, levels
only difference noted was (at station*	3

of the TKN values, (TKN values include
represented a disproportional share or cne

both NH^ and organic nitrogen).

Dissolved oxygen data (Table 7) revealed many violations of Florida

Water Quality Standards (DO-min of 4.0 pp» and avg. of 5.0 mg/1) at depth.

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TABLE 6
WATER QUALITY DATA
TIDAL CANALS
SANIBEL ISLAND, FLORIDA

STATION NQ2-N03

E-l
Max.
Min.
Mean

E-2
Max.
Min.
Mean

E-3
Max.
Min.
Mean

E-4
Max.
Min.
Mean

E-5
Max
Min.
Mean

E-6
Max.
Min.
Mean

E-7
Max.
Min.
Mean

E-8
Max.
Min.
Mean

E-9
Max.
yfin.
tfean

<0.01
<0.01
<0.01

<0.01
<0.01
<0.01

<0.01
<0.01
<0.01

<0.01
<0.01
<0.01

<0.01
<0.01
<0.01

<0.01
<0.01
<0.01

<0.01
<0.01
<0.01

<0.01
<0.01
<0.01

<0.01
<0.01
<0.01

NHi

0.29
0.20
0.24

0.40
0.20
0.30

0.17
0.10
0.13

0.05
0.01
0.03

0.05
0.05
0.05

0.08
0.05
0.06

0.05
0.01
0.03

0.05
0.01
0.03

0.01
0.01
0.01

TKN

0.30
0.25
0.27

0.25
0.20
0.22

0.25
0.20
0.22

0.40
0.12
0.26

0.23
0.12
0.17

0.60
0.20
0.40

0.55
0.25
0.40

0.25
0.20
0.22

0.25
0.20
0.22

T-P

0.07
0.06
0.07

0.07
0.06
0.06

0.08
0.06
0.07

0.13
0.07
0.01

0.08
0.08
0.08

0.10
0.08
0.09

0.08
0.08
0.08

0.08
0.08
0.08

0.08
0.08
0.08

TOC

8.5
7.5
8.0

6.3
4.5

5.4

4.5
4.0
4.2

5.3
3.5

4.4

5.2
4.8
5

5.8

5.6

5.7

5.2
5.2
5.2

5.3
4.8
5.0

4.7

4.5

4.6

T-N

0.31
0.26
0.28

0.26
0.21
0.22

0.26
0.21
0.23

0.41
0.13
0.27

0.24
0.13
0.18

0.61
0.21
0.41

0.56
0.26
0.41

0.26
0.21
0.23

0.26
0.21
0.23

E-1Q
"lax.
¦lin.
¦lean

<0.01
<0.01
<0.01

0.01
0.01
0.01

0.45
0.20
0.32

.09
.08
.08

4.5
4.0
4.2

0.46
0.21
0.33

S-ll
lax.
lin.
lean

<0.01
<0.01
<0.01

0.01
0.01
0.01

0.30
0.20
0.25

0.11
0.10
0.10

5.0
4.5
4.7

0.31
0.21
0.26

ote:

All values In mg/1

13

-------
TABLE 7

DISSOLVED OXYGEN. SALINITY AND TEMPERATURE
TIDAL CANALS
SANIBEL ISLAND, FLORIDA

STATION

£81
1:81

F.-01
F-01
t-ol
E-01
F -0)
f -01
F-01
E-01

E-02
E-02
E-02
F -02
E-02
E-02
£ -02
F -02
F - 02
E-(i2
E-02

F -03
£-03
F-C3
E -03
E-03
F -03
E-03
E-C3
E-03

E-P4
F-04
E-04
E -04
E-04
E-04
E-O*
E-04
E-O*
E -04
E-04

E-05
E -OS
E-Ob
E-u5
E-05

E-06
t -06

f.ftb

E-06
F-C6
E-06
t--j6
E-06
E-06
t -06
F-06
E-06
E-06
E-06
E-06

m
m

1:8?

E-07
E-07

E-08
E-Ob
E -08
E-08
E-08
E-08
E-08
E-08
E-08

E-09
E -09

F -09
F-09
E-,19
E-C9
E-09

-.-10
- -1 0
¦ -10
-10
: -1 0

L -1 o

;:li
>11

DEPTH
FT

1

2

3

4

5

6

7

a
9

10

11

12

1

2

3

4

5

6

7

8

9

10

11

1

2

3

4

5

6

7

e

9

1

2

3

4

5

6

7

8

9

10

11

1

2

3

4

5

1

2

3

4

5

6

7

8

9

1?
IS

14

15

1

2

3

4

5

6

7

8

3

4

5

6

6.5

00 "G/L
MAX HIN MEAN

6.1

l\ 1

8.0
7 .4

7.2
7.u
6.0
5.2
4.2
3. -»

6.2
6.1

7.0

M

6 . 7
fe.b
b.B

5.1
5.0
4.7
4.0

6.3
t>.»
6.a

6.4

S.-4

tu

6.7

6.7

7.2
6.9

6.8
6.1

5.0

4.8
2.0

B.O
8.0
6.6
6 • 2

6.5
6.5
6.3
6.5

6.5

6.5

6.5

6.5
6.5

6
6.
6.6
6.6
6.6

5.1

5.0
4.9
4.8
4.8

4.6
4.5

3.7

3.1

2.4

1.5

5.1

5.0

5.2
5.2

5.1
5.0
4.8

4.7
4 .0

3.8
2.5

4.9

4.8

4.7
4.6
4*6
4.5
3.5

3.9

5.8

5.0
5.2

5.1

5.2

5.5

"*§

3.9

1.9
0.6

5.6
5.6

1:1

6.4	6.0
6.3 6.9

6.5	5.9

5.9
5.9

5*§

5.8

5'2

5.5
5.0

*'l

4.9

4 4
6 4
6 4

,6.

,6

,5

9.0

9.0

9.1
9.4

8*5

8.0
7.4

6."

lii

4.9

6.0

6.0

6.1
6.1
6.1

M
M

4.0
3.7
3.4

5.5

5.6

5.7

5.8
5.6
5.6
5.4

4.6
4.2
3.2

2.4

3.0

5.7

5.6

5.8

5.9

5.7

5.5
5.2

4.8

4.5

*3:i

5.7

5.7

5.6

5.4

5.5

5.5

4.8

4.2

4.1

6.3

5.9
6.1
6.1
6.0

6.0
5.3

4.6

i:ls

0.6

6,8
6.8

6.1

5.8
4.5

6.2
6.2
6.2

5.9
6.2

6.2
6.1
6.1
6.1

6.0

5.7
5.7
5.7
6.5

6.5

5.6

5.5

5.6

5.6

*•?
S:l

1:1

?:?

7.3

7.1

6.7

5.7

5.4

5-2

4.8

4.5

*•5
*•?
3.0

2.6

7.6

i

7.5
?:§

m
e.|

6.2

7.9

MAX

36.0
3b.0
36.0
3b.9

36.0

36.1

36.0

36.1
36.1
36.1
36.1

36.0

36.0
35.9
35.9
36.9

36.1

36.2
36.1
36.1
36. 1
36.1

36.0

36.0
35.9
35.9

36.1

36.0

36.1

36.0

36.1

36.0

36.2

36.1

36.2
36.2
36.1,

36.1

36.2
35.7
36.2

35.8
35.4

35.6

35.7

35.3
35.3
35.3

35.3
35.3
35.3
35.3
35.3
35.3
35.3
35.3
35.3

SAL (0/00)

M1N

35.5

35.6
3b.4
35.3
3b.4
3b.3
3b.3
35.2
35.2
3b. 2
35.2

35.6
3b.6
3b.8

35.8

35.9
35.9
3b.9
35.9
35.9
35.9
35.8

35.5

35.6

35.8

35.9

35.7

35.8

35.9
35.9
36.0

35.2

35.4

35.5

35.6

35.7
35.7
35.7
35.7

35.7

35.8

35.4
34.7
34.7
35.0

34.0
34.0

34.0

34.1
34.1
33.9
33.9
34.1
34.5
35.9
36.1
36.1

MEAN

35,8

35.6
35.8

35.7

35.8
35.8
35.7
35.7
35.7
35.7
35.7

35.8
35.8
3b.8
35.8

36.2	;
36.0
36.0
36.0
36.0
36.0
35.95

35.8

35.9
35.9
35.9
35.9
35.9
36.0

36.0

36.1

35.6
35.6
35.8
35.8

35.6
35.8
35.8
35.8

35.7
24.0
36.0

35.6

35.0

35.1

35.3

35.7

34.6
34.6

34.6
34.0

34.7
34.7
34.6

34.6

34.7
34.7

35.6

35.7

35.7
35.3

35.3

31:5

§!:!¦'¦

35.4

35.5

35.6
35.5

11:1

35.4

35.5

35.8
35.8
35.8
35.8
35.8

35.4

35.5

35.6

35.7

35.8
35.8
35.8

TEMP (CI
MAX WIN MEAN

31.0
31.0
32.0
32.0
31.0
31.0
30.5
30.0
30.0
3u. 0
30.0

32.5
32.0
31 .5
31.0

31.0

30.1

30.1

30.2
30.2
30.1
30.0

32.0
32.0
32.0
32.0

31.0
30.5

30.1
30.1

32.0
32.0
31.0
30.5
30.0
30.0
30.0
29.7
29.7
29.7

31.3

31.4
30.6
30.6

29.7
29.9
29.7

29.7
29.7
2?.7
29.7
29.7
29,6
29.6
29.6
29.6

33.0
33.0
33.0
33.0
32.5

il.i
11:1

31.0

29.8
29.8
2V.B

29.6
24.b

29.8

29.7

29.3

29.4
29.4
29.7

30.0
30 • 0

29.9
29.9
29.9

29.6

29.7
29.7
29.7
29.7

29.7

29.9

29.8
29.6

29.9
29.8
29.8
29,8
29.8

29.6

29.7

29.8
29,3

29.3

29.4

29.5
29,4
29.4
29.4

29.7
29.7
29.7
29.7

29.5

29.6
29.5

29.5
29.4
29.4
29.4
29.4
29.3
29.3
29.3
29.3

30.9
30.9
30.7
30.6
30.5

30.9
31.0
30.9
30.6
30.3
30.3
30.3

31.1
30.9
30.7
30.5
30.4

30.8
30.8

30.5
3U • 45
30.2

30.2
30.0
29.«
29.7

29.7

29.8

29.6

31.0

30.9

30.6

30.3
30.3
29.9
29.9
29.9
29.9
29.9
29.9

30.7
30.7
3U.7
30.7

30.3

30.2
29.9

30.0

29.7

30.4

30.4

30.1

29.8
29.7
29.7
29.7

29.5
29.5
29.5

29.3

30.5

30.5
30.1

30.1

29.9

29.6

29.7

29.6
29.5

29.7
29.5
29.5
29.5

29.5

29.4
29.4
29.4

29.4

29.6
29.6

31.9
31.9

11:1

31.5

30.6
30.5

30.5

Mil

31.0
30.9

30.6

30.6
30.3
30.3

32.0

31.7

31.6

31.2

30.7

30.3

32.0
32.0
32.0
32.0
>2.0

33.0
33.0
33.0
31.5

11

16

-------
exceeding 6 to 8 feet at mean tide level (5-7 feet mlw). These violations
:an be attributed to poor circulation in excessively deep canals. Nutrient
Inputs from drainfields are aggravating functions due to their oxygen consuming
:haracteristics.

'.stuarine Water Bacterial Quality

Samples for fecal coliform bacteria analysis were collected in conjunction
rith the above water quality sampling program. Salmonella swabs were installed
t stations E-l thru E-6.

Results of the bacteriological analyses are given in Table 8. All fecal
oliform counts were less than two per 100 ml. Bacterial quality of these
aters, based upon this sampling program, is excellent. In addition, no
almonella colonies were isolated.

17

-------
TABLE 8
TIDAL CANALS
FECAL COLIFORM BACTERIA DENSITIES^





SANIBEL ISLAND, FLORIDA





STATION

6/10
AM PM

6/11
AM PM

AM

6/12

PM

E-l

<2

<2 <2

<2



E-2

<2

<2 <2

<2



E-3

<2

<2 <2

<2



E-4

<2

<2 <2

<2



E-5

<2

<2 <2

<2



E-6

<2

<2 <2

<2



E-7





<2

<2

E-8





<2

<2

E-9





<2

<2

E-10





<2

<2

E-ll





<2

<2

Note:

5 tube mpn - Fecal

Coliforms/100 ml.





18

-------
FIGURE 1

STUDY AREA
SANIBEL ISLAND, FLORIDA

-------
FIGURE 2
SEPTIC TANK STUDY SITES
SANIBEL ISLAND, FLORIDA

-------
FIGURE 3
WEST ROCKS SUBDIVISION
SANIBEL, FLORIDA

21

-------
WEST ROCKS LAKE

0»7

W4-

ABSORPTION FIELD-

UNIT 27

( UMLAND RESIDENCE)

W3V

W,6
O

SEPTIC
TANK

HOUSE
SEWER

WELL

OBSERVATION WELLS-

%2

PROPERTY
BOUNDARY

W1

-o

0
u

10

	I—

20 FEET

COQUINA DRIVE

FIGURE 4
UNIT 27 WEST ROCK SUBDIVISION
SANIBEL, FLORIDA

22

-------
Staff

Gu ge _ w 13	WEST ROCKS LAKE

6 0 o

FIGURE 5
UNIT 29
WEST ROCKS SUBDIVISION
SANIBEL, FLORIDA

23

-------
fO

¦ts

FIGURE 6
STATION locations
FSTUARINE area
SANIBEL ISLAND, FLORIDA

-------
FIGURE 7
GROUNDWATER LEVELS
SANIBEL ISLAND, FLORIDA

DISTANCE (FEET)

-------