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 ------- 77- WATER QUALITY AND SANITARY SURVEY SANIBEL ISLAND, FLORIDA JUNE, 1977 >i Ay - ¦ , '-'.V # . a or . ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 3 ------- 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! A ------- 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 5 ------- 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. 6 ------- 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. 7 ------- 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 8 ------- 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 9 ------- 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. 10 ------- 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. ------- 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 12 ------- 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. 13 ------- 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. 14 ------- 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) ------- |