1. Watershed and water quality assessment of the Allen’s Creek watershed David A. Tomasko, Ph.D. Cheryl Propst, M.S. May 16, 2012

2. Allen’s Creek Water Quality Stations

3. Marine stations predominate – example station locations

4. Station 19-02 Belcher Road Saltwater Site

5. Station 19-04 St. Paul’s Drive Saltwater Site

6. Station 19-06 Bellair Road Saltwater Site

7. Station 19-03 Longbow Lane Freshwater Site

8. Station 19-05 Bellair Road Freshwater Site Shelf under Bellair Road bridge prevents brackish water from flowing upstream during incoming tide Red mangroves and horses downstream of Bellair Road culverts. Lift station on upstream side.

9. Station 19-10 Kent Place Freshwater Site Black mangroves appear in tidal area downstream where tributary meets Allen’s Creek Outside* of WBID Sample upstream of culvert

10. How is water quality at these sites? Rather than WBID as a whole, data looked at station by station Water quality data compared to IWR criteria Number of “exceedances” compared to verified list criteria

11. FDEP Screening Criteria Station Summary Station*Marine/Freshwater Chl a CorrectedBODDO Fecal Coliforms 21FLPDEM19-01Marine 54/1559/1734/1518/16 21FLPDEM19-02Marine 68/1482/2134/1516/16 21FLPDEM19-03Freshwater ID 64/21ID 21FLPDEM19-04Marine 78/19ID58/21ID 21FLPDEM19-06Marine 71/21ID50/21ID 21FLTPA27554138244454Marine ID 52/22ID 21FLPDEM19-10Freshwater ID69/1676/18 *Stations with N≥25 at a depth of ≤ 0.5m ID = Insufficient Data Mean Value Above Target and Meets Verified List Criteria Mean Value Below Target but Verified Impaired due to % Exceedance <10% Exceedance 0% Exceedance Percent exceedance criteria vary with sample size. Numbers within cells represent – Actual % Exceedance / % Exceedance Criteria.

12. Findings Most marine sites had levels of Chl-a in excess of IWR guidance (11 ug / liter) and would also exceed criteria for Old Tampa Bay Stations 1 and 2 exceed for Chl-a, BOD, DO and fecal colifom bacteria DO criteria is being revised by FDEP – Allens Creek not a trout stream Bacteria impairments the basis for existing TMDL

13. Does fecal coliform bacteria exceedance mean sewage leaks? Perhaps leaks are involved, but… Impacts of birds are well documented in literature – Estimates in prior TMDLs of 200 to 400 million fecal coliform bacteria per bird per day – humans about 2 billion per day Using low end estimate, one bird could cause 13,000 gallons of water to exceed 400 CFU / 100 ml Experiment in Clam Bay (Collier County) - – Source ID work found no evidence of human impacts (nor did sewage collection system operators) – Variety of bird fecal “events” sampled – Highest range was > 200,000 fecal coliform bacteria from one bird (white ibis) from one event It is within the realm of possibilities that birds are an important source of bacteria in Allens Creek – Additional source identification efforts could be warranted

14. Photo from Estero Bay, Lee County

15. Does exceedance of Chl-a mean nutrient enrichment is to blame? Data from marine and freshwater stations were compared to screening criteria used by FDEP and EPA for TMDL loading models Additional screening criteria used – FDEP’s recently adopted NNC criteria – EMC values for residential stormwater runoff – EMC values for forested uplands (for comparison) – Locally-derived TN and TP from regression equations vs. Chl-a and appropriate targets (11 and 20 ug / liter)

16. Freshwater Screening Level Criteria Forested Uplands EMC valueSingle Family Residential EMC Value FDEP NNC Criteria TMDL Targets Sarasota Bay (Heyl 1992) 1993 TBEP Loading Model Sarasota Bay (Heyl 1992) 62-302 F.A.C. (regional streams) TN (mg/l)1.601.021.901.871.54 TP (mg/l)0.220.160.310.390.12 Marine Screening Level Criteria Forested Uplands EMC valueSingle Family Residential EMC Value FDEP NNC Criteria TMDL Targets Sarasota Bay (Heyl 1992) 1993 TBEP Loading Model Sarasota Bay (Heyl 1992) 62-302 F.A.C. (Old Tampa Bay) TN (mg/l)1.001.021.91.871.08 TP (mg/l)0.190.160.310.390.23

17. FDEP Screening Criteria Station Summary Station*Marine/Freshwater Chl a CorrectedTNTPBODDO Fecal Coliforms 21FLPDEM19-01Marine 54/1526/1583/1559/1734/1518/16 21FLPDEM19-02Marine 68/1422/1556/1582/2134/1516/16 21FLPDEM19-03Freshwater ID6/1936/21ID64/21ID 21FLPDEM19-04Marine 78/1977/1991/21ID58/21ID 21FLPDEM19-06Marine 71/2182/2148/21ID50/21ID 21FLTPA27554138244454Marine ID 52/22ID 21FLPDEM19-10Freshwater 3/1643/16ID69/1676/18 *Stations with N≥25 at a depth of ≤ 0.5m ID = Insufficient Data Mean Value Above Target and Meets Verified List Criteria Mean Value Below Target but Verified Impaired due to % Exceedance <10% Exceedance 0% Exceedance Percent exceedance criteria vary with sample size. Numbers within cells represent - Actual % Exceedance / % Exceedance Criteria.

18. Nutrient-related “exceedances” Highest exceedance rates are at marine sites at St. Paul’s Drive and Bellair Road (19-04 and 19- 06) Other marine sites exceeded criteria thresholds, but mean value below target criteria Neither freshwater sites had TN exceedance – This is where nutrients come from TP exceedance was widespread – But is TP the likely limiting nutrient?

20. Targets determined using regression analysis were based on chlorophyll a criteria of 11 µg/l

22. Targets determined using regression analysis were based on chlorophyll a criteria of 20 µg/l

24. Is there a relationship between nutrients and corrected chlorophyll a levels? Station Mean TN:TP TN Correlation TN Regression R 2 TP Correlation TP Regression R 2 21FLPDEM19-01 3.26 X0.144X0.151 21FLPDEM19-02 3.86 X*0.181X0.137 21FLPDEM19-03 5.50 21FLPDEM19-04 4.78 X*0.231 21FLPDEM19-06 6.81 X*0.233 21FLPDEM19-10 4.59 21FLTPA 27554138244454 4.89 X*0.315X*0.649 All Freshwater Stations X*0.516 All Saltwater Stations0.869X*0.15 Significant correlation defined at p<0.05 *Not normal distribution

25. Is there a relationship between nutrients and salinity levels? Station Marine or Freshwater TN Correlation TN Regression R 2 TP Correlation TP Regression R 2 21FLPDEM19-01MarineX0.843 21FLPDEM19-02MarineX*0.750 21FLPDEM19-04Marine 21FLPDEM19-06Marine X*0.165 All StationsMixedX*0.442X*0.159 Significant correlation defined at p<0.05 *Not normal distribution **N<20

26. Recommendations moving forward Source identification efforts and focused efforts to document potential role of birds on bacteria within Allen's Creek Work with FDEP to ensure reasonableness of proposed alternative DO criteria for freshwater and marine waters

27. Recommendations moving forward Based on TN:TP ratios, phosphorus not a nutrient of concern for eutrophication – Exceedances may have more to do with regional geology than eutrophication Work with FDEP to develop site-specific alternative criteria for TN (and maybe TP) – Regression analysis to develop TN for 11 and 20 ug /liter for marine and freshwater stations – Develop salinity-normalized TN and TP targets for regular reporting (e.g., Clam Bay’s SSAC in 62-302) Ensure that loading model used is appropriate for developing load reduction targets for various stations

28. Questions or comments?