Septic System Impacts on Stormwater and Impaired Waterbodies December 8, 2016 Tim Denison, Johnson Engineering Marcy Frick, Tetra Tech
Presentation Overview Charlotte County: Many areas adjacent to impaired waterways Wastewater septic systems Stormwater overland drainage flows County-wide plan to provide central sewer and improve stormwater quality North Shore neighborhood: Pilot project for septic system removal East and West Spring Lakes area: First large-scale septic system removal project 2
North Shore Neighborhood Pilot Project 3
North Shore Small scale pilot project of 42 lots along Charlotte Harbor Typical ¼ acre residential area with roadside swales Septic systems from 1960s are inadequate and failing Pose health hazard during large rain events 2008 DOH standing water samples >47,000 cfu/100ml fecal Drains to Peace River & Charlotte Harbor Both impaired for nutrients 4
BMPs Remove septic tanks and connect to central sewer Restore and rehabilitate swale system Re-establish original swales Replace culvert pipes Replace sediment with proper fill Replace vegetation Public education Neighborhood meetings/workshops Florida Friendly Landscaping book Fertilizer ordinance information Pre-construction 5
Monitoring Stormwater (pre/post construction rain events) 3 grab sample sites - DOH site comparison - Distributed runoff inflow - Northshore Drive swale outflow 1 combined stormwater outfall site - Automated composite sampler - Rain gauge and flowmeter Ground water (quarterly throughout) 3 ground water monitoring wells Pre-construction 6
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Stormwater Sampling 3 sets of pre-construction samples in summer 2013 Pre-construction Pre-construction 8
Construction Septic tanks removal, sewer connection, and swale restoration fall 2014 spring 2015 9
Stormwater Sampling 5 sets of post-construction samples in summer 2015 Pre-construction Post-construction 10
Stormwater Sampling - TN 11
Stormwater Sampling - Ammonia 12
Stormwater Sampling - NOx 13
Stormwater Sampling - TP 14
Stormwater Sampling - TSS 15
Ground Water Sampling 16
Ground Water Sampling, cont. 17
Ground Water Sampling, cont. 18
Conclusions Stormwater monitoring Significant reduction in stormwater runoff water levels observed No reduction in nutrient concentration measured within first 6 months Ground water monitoring Significant reduction in nitrogen concentrations at GW1 and GW3 No measurable reduction in nitrogen concentrations at GW2 due to tidal influence 3 neighboring properties outside of project area that are still on septic systems Pollutant volume removal Annual septic tank effluent converted to treated wastewater is approximately 2,100,000 gallons 19
Challenges Flow volume data Problem: Stormwater discharge flow velocity too low to measure Solution: County provided metered water use data for all properties Sewer connections Problem: A few homes along west project boundary still on septic Solution: Collect additional samples Ground water level data Problem: Not able to determine drain field level vs. ground water level Solution: Recommend continuous water level instruments in future Problem: Area is saturated at all times with the tides Solution: Sample only on the outgoing tide 20
East and West Spring Lakes Full-Scale Project 21
East and West Spring Lakes Septic systems were constructed between the 1950s and early 1980s Many are in failure and do not meet current regulations Area ultimately discharges to Charlotte Harbor and Peace River Project goals: Construct central wastewater service to 2,455 properties Restore the stormwater conveyance system Educate property owners on BMPs for fertilizer, pesticide, and herbicide application 22
Monitoring 49 ground water monitoring wells and 22 canal monitoring sites Ongoing since 2012 Slight modifications to canal locations in 2015 5 stormwater outfall monitoring sites Monitoring to meet grant requirements Pre-construction samples from September 2015 May 2016 23
Phase I sample sites: Sunrise Canal Elkham Waterway 24
Phase II sample sites: West Spring Lake Tarpon Waterway East Spring Lake 25
Sampling Parameters Parameter Analysis Type Sample Type Total suspended solids Laboratory Composite Total phosphorus Laboratory Composite Nitrate + nitrite Laboratory Composite Total Kjeldahl nitrogen Laboratory Composite Ammonia Laboratory Composite Total nitrogen Laboratory Composite Biochemical oxygen demand Laboratory Composite Fecal coliform Laboratory Grab Temperature Field Meter ph Field Meter Specific conductance Field Meter Dissolved oxygen Field Meter Turbidity Field Meter Water level (at ground water monitoring wells) Field Meter Rainfall Field Meter 26
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Regulatory Standards Canals and stormwater outfalls: West Central Nutrient Region: TN = 1.65 mg/l and TP = 0.49 mg/l Fecal coliforms = 400 cfu/100 ml Ground water monitoring wells: Drinking water standards: NOx = 11 mg/l Fecal coliforms = presence detected 28
Canal Results - NOx Year Number Minimum Maximum Median Mean (mg/l) (mg/l) (mg/l) (mg/l) 2012 27 0.004 0.13 0.018 0.025 2013 120 0.004 0.833 0.022 0.043 2014 111 0.004 0.151 0.016 0.031 2015 124 0.002 0.391 0.012 0.028 2016 88 0.004 0.174 0.020 0.036 29
Canal Results - TN Year Number Minimum Maximum Median Mean Number of (mg/l) (mg/l) (mg/l) (mg/l) Exceedances % Exceedances 2015 44 0.533 1.480 1.009 1.003 0 0% 2016 88 0.590 1.540 0.910 0.944 0 0% 30
Canal Results - TP Year Number Minimum Maximum Median Mean Number of (mg/l) (mg/l) (mg/l) (mg/l) Exceedances % Exceedances 2012 27 0.220 0.660 0.400 0.414 9 33% 2013 120 0.010 0.900 0.230 0.256 14 12% 2014 111 0.020 0.440 0.210 0.225 0 0% 2015 124 0.008 0.538 0.121 0.135 2 2% 2016 88 0.028 0.580 0.196 0.221 4 5% 31
Canal Results Fecal Coliforms Minimum Maximum Median Mean Number of Year Number (#/100 ml) (#/100 ml) (#/100 ml) (#/100 ml) Exceedances % Exceedances 2012 27 10 90 30 36 0 0% 2013 120 1 1,400 20 60 3 3% 2014 111 10 1,050 20 46 1 1% 2015 124 10 620 20 58 1 1% 2016 88 10 8,600 60 414 15 17% 32
Ground Water Results - NOx Year Number Minimum Maximum Median Mean Number of (mg/l) (mg/l) (mg/l) (mg/l) Exceedances % Exceedances 2012 98 0.004 19.439 0.012 0.394 1 1% 2013 288 0.004 39.170 0.015 1.158 12 4% 2014 272 0.007 58.157 0.034 2.195 17 6% 2015 233 0.004 57.800 0.101 1.522 9 4% 2016 166 0.004 49.300 0.071 2.288 12 7% 33
Ground Water Results - TN Year Number Minimum Maximum Median Mean (mg/l) (mg/l) (mg/l) (mg/l) 2015 88 0.35 54.3 1.46 5.23 2016 166 0.23 51.7 1.48 4.17 34
Ground Water Results - TP Year Number Minimum Maximum Median Mean (mg/l) (mg/l) (mg/l) (mg/l) 2012 98 0.02 13.53 0.75 1.21 2013 288 0.08 76.20 0.97 2.72 2014 272 0.04 41.94 2.34 2.34 2015 233 0.01 105.00 0.80 2.59 2016 166 0.008 13.5 0.68 1.38 35
Ground Water Results Fecal Coliforms Year Number Minimum Maximum Median Mean (#/100 ml) (#/100 ml) (#/100 ml) (#/100 ml) 2012 98 10 2,940 10 84 2013 288 3 270 10 12 2014 271 10 1,060 10 22 2015 233 1 520 10 15 2016 166 10 840 10 18 36
Stormwater Pre-Construction Results - TN Area Number of % Samples Exceedances Phase I 8 12.5% Phase II 12 50.0% 37
Stormwater Pre-Construction Results - TP Area Number of % Samples Exceedances Phase I 8 75.0% Phase II 12 100.0% 38
Stormwater Pre-Construction Results Fecal Coliforms Area Number of % Samples Exceedances Phase I 6 100.0% Phase II 12 100.0% 39
Data Loggers Installed data loggers on existing ground water monitoring wells: 1 in Phase I 2 in Phase II Purpose is to demonstrate the change in water levels prior to and after removal of septic systems Change in water level is an important factor in determining pre- and post- project trends 40
Next Steps County has been removing septic systems and connecting properties to central sewer in Phase II Post-construction sampling planned for the 2017 wet season County is now constructing the wastewater collection system in Phase I Septic system abandonment will begin in 2017 Post-construction sampling planned for the 2018 wet season Continue to collect ground water well and canal data Data will be used to evaluate the nutrient and fecal coliform reductions from project implementation 41
Questions? Tim Denison, Johnson Engineering Senior Environmental Scientist (239) 461-2458 tdenison@johnsoneng.com Marcy Frick, REM, Tetra Tech Water Resources Engineer (850) 536-8115 marcy.frick@tetratech.com 42