Kensico Action Plan: Protecting Water Quality with a Dual Strategy

1. Kensico Action Plan’s Dual Strategy of Offense and Defense to Protect Water Quality 2008 Watershed Science & Technical Conference September 17, 2008 Guy Apicella Dale Borchert

2. New York City Granted Historic Ten-Year Filtration Avoidance Determination AgreementMayor Bloomberg and US Environmental Protection Agency (EPA) Administrator Steve Johnson have announced the issuance of a 10-year Filtration Avoidance Determination (FAD) by the EPA for the City’s Catskill/Delaware drinking water supply system (July 30, 2007) Kensico is Terminal Reservoir for Catskill-Delaware system

3. KAP Project Tasks Item 1 Data Compilation & Development Item 2 Delineate Kensico Subbasins Item 3 Model Stormwater Discharges Item 4 Recommendations for Pollution Remediation Item 5 Visual Inspection of Sanitary Sewers Item 6 Water Quality Risk Assessment Item 7 Effluent Chamber Dredging Item 8 Kensico Action Plan

4. 108 Model Sub-basins NEW YORK CONNECTICUT

6. TSS Load Contribution from Kensico Sub-basins

7. Fecal Coliform Load Contribution from Kensico Sub-basins

8. Kensico Watershed Protection Provided By KAP • Offense • Best Management Practices • Remediation of stormwater pollutant loadings • Extension of BMPs constructed and in operation • Defense • Water Quality Risk Assessments • Identify on-site conditions that may pose a threat to water quality • Conduct qualitative risk assessment of selected sites

9. Four Stormwater Remediations (BMP) Designs • N1 West Lake Drive Located on West Lake Drive • N7 Pipeline System Located off Old Kensico Road between private property and the Kensico Reservoir • N12 Extended Detention Basin Located off Nanny Hagen Road • Whippoorwill Stream Rehabilitation Located within Whippoorwill Creek off Nanny Hagen Road in the Towns of North Castle and Mount Pleasant

10. Whippoorwill Stream Stabilization • Largest sub-basin (1.5 sq. mi) • Highest TSS/FC loading • Lower reach of stream unstable despite spot stabilization (rip-rap)

12. Whippoorwill Stream Stabilization Conceptual Plan • Bioengineering techniques to control grade and direct flow through natural channel • Rosgen method • Remedial measures: • Cross vanes • J-hooks • Bank rock toe key, coir log & vegetation

13. Objectives of Cross-vanes: • Establish Grade Control • Dissipate Energy • Reduce Stream bank erosion by reducing near bank stress. • Enhance fish habitat • Maintain width to depth ratio • Reduce flooding with bankfull benchs • Withstand large floods • Be visually acceptable to the public

16. Cross Vane with Step – NY

17. Step Pools - PA.

18. Extended Detention Basin for N12 Sub-basin • Drainage area – 102 acres • 10% impervious • Design according to NYSDEC Phase 2 regulations • Total storage capacity -100,500 cu. ft, 751,600 gal. • “Wet” surface area – 0.6 acres • Max depth – 7 ft

19. N12 – EXTENDED DETENTION BASIN Site is between Nanny Hagen Road and Kensico Reservoir

20. Site Plan N12 – Extended Detention Basin (EDB)

21. Innovative Feature of N12 EDB • Off-line storage • Inlet Structure has 3 flow paths • Baseflow routed directly to Kensico Reservoir • Stormwater runoff flow routed to EDB • Flows > 2 year storm by-pass EDB into Kensico Reservoir • Valve on inlet pipe to EDB to prevent scour of settled solids • Flow monitoring and sampling provisions

22. Inlet and Outlet Chambers N12 – EXTENDED DETENTION BASIN

23. N1 - West Lake Drive Drainage Improvement • Storm water from the N1 sub-basin bypasses BMP13 during high rainfalls and flows down West Lake Drive into Malcolm Brook • Two new double catch basins • Reconstruction of the existing headwall and rip-rap channel to the existing V-notch weir.

24. N7 – Pipeline System • Steep stream has washed out rip-rap and erosion • Installation of a new 36” pipe line from discharge point to Reservoir • Construction of a new rip-rap outfall • Placement of the Stormwater Treatment Unit

25. Water Quality Risk Assessments • Westchester County Airport • General aviation & corporate aircraft facility located near Rye Lake • Turf chemicals in Sub-basin N5 • DEP sampling for herbicides/pesticides identified N5 for 2,4-D • Swiss Re Office Complex • Identify any potential contaminant source from facility located in Bear Gutter sub-basin

26. Westchester County Airport Water Quality Risk Assessment • 703 acre facility • Northwest part drains into Rye Lake • On-site survey and regulatory review • Stormwater runoff from aviation surfaces flow into detention basins or Blind Brook (tributary to Long Island Sound) • Permits and compliance programs reviewed • NYCDEP tracks spills and plans for improvement • No significant human health risk indicated

27. Turf Chemicals in Sub-basin N5Water Quality Risk Assessment • N5 drainage area is 268 acres (4 % of total Kensico DA) • DEP collected 44 samples in 2005; 4 0f 5 “hits” for 2,4-D at N5 • Literature review of herbicides, 2,4-Dichlorophenoxyacetic acid (2,4-D) • Administered questionnaire survey to residents of sub-basin N5 on lawn care products and application • 630 residential & 130 commercial surveys mailed • 82 residential & 7 commercial surveys received • 53% residential use of products found • WinSLAMM applied to model loading from landscaped areas in GIS • Loading rate on 53% of small landscaped areas yielded concentration ~ average of DEP sampling data (0.15 ug/l) • Federal Water Quality Criterion is 100 ug/l; Max measurement was 1.6 ug/l • No significant human health risk

28. Swiss Re Office ComplexWater Quality Risk Assessmnet • 126 acre property west of Route 120 • On-site survey and regulatory review focused on: • Stormwater management practices • Chemical & fuel handling practices • Facility operations (e.g., solid waste) • Environmental compliance programs • Water quality/detention basins and grass woodland buffers mitigate stormwater impact • EMS/ISO 14001 Certification • Finding: chemical transport to reservoir is not indicated

29. KAP Dual Strategy Conclusions • Stormwater BMP construction and operation will continue to reduce pollutant loadings • Water quality risk assessments investigated potential threats and found no substantial risks • NYCDEP continues to operate Catskill-Delaware system under FAD

30. Questions