SUNY ESF Workshop Shohreh Karimipour, P.E. Enhanced Phosphorus Removal Standards NEW YORK STATE DEPARTMENT OF ENVIRONMENTAL CONSERVATION

Purpose To develop an effective and technically defensible criteria to address stormwater design standards in phosphorus-limited watersheds –EOH NYC Water Supplies Watersheds –Greenwood Lake –Onondaga Lake A supplement to the Existing New York State Stormwater Management Design Manual for enhanced phosphorus control –Provide consistency with NYCDEP watershed rules – Enhanced Criteria consistent with the current State standards

Overview Existing Stormwater Design Standards –New York State –Watershed Rules Enhanced Standards (Supplement) – Defining Enhanced Phosphorus Removal – Overview of Development Process – Recommendations Design Standards – Sizing Criteria – Performance Criteria

Marcus Quigley, P.E. Project Manager Eric Strecker, Principal-In-Charge GeoSyntec Consultants Robert Pitt, Senior Technical Specialist and Technical Review NYS DEC, Project Management Technical Advisory Group (TAG) NYCDEP NYSSWCC NYSOAG River Keepers (CEA) Insite Engineering The Project Team University of Alabama

Design Standards NYS Requirements Sizing Criteria – Capture & treatment 90% Design Storm – Channel protection and flood controls Performance Criteria – Removal Efficiency: 80% TSS 40% phosphorus – Standard management practices – Design Specifications Can capture and treat the full water quality volume Provide pretreatment Have acceptable longevity in the field

Features of Standard Systems Examples: Embankment Specifications Principal/Emergency Spillway Inlet Protection Adequate Outfall Protection Sediment Forebay Media specifications Adequate WQv Multiple Treatment Pathways Minimum Geometry Pond Benches Pondscaping Plan Wetland Elements Pond Buffers / Setbacks Non-clogging Orifice Riser in Embankment Adjustable Gate Valve Safety Features Maintenance Responsibility Maintenance Access Maintenance Schedule

Watershed Rules The Croton Watershed –Sizing Criteria Detention of 2-yr., 24-hr. storm TR-55 calculation method Pollutant load analysis 2-yr, 10-yr, 25-yr, 100-yr peak control –Performance Criteria infiltration, retention, detention Onondaga Lake Greenwood Lake

Defining Enhanced Performance Criteria How much stormwater is prevented? –Hydrologic Source Control –Evapotranspiration –Infiltration How much of the remaining stormwater is treated? –Hydraulic function –Capture and treatment –Bypass What is the effluent quality of the treated runoff? –Effluent quality of the discharge –Seasonal Performance Criteria

Phosphorus and Treatability Particulate vs. dissolved forms Particulate size or settling velocities International BMP Database Research by Pitt, et al. (Wisconsin) P association with particles < 10 µm 51,90063,10078,8006,6402,16017,2006,400 Average mgP/kgSS µm 1-2 µm 2-10 µm µm µm µm >250 µm Particle size

Sizing analysis as a function of Treatment volume Detention time Permanent pool Particle settling theory – Continuous simulation SWMM modeling 44 yr hourly data (Carmel) 120 Model runs –Event simulation by HydroCAD® Detention time Seven scenarios (WQv) Permanent Pool Extended Detention outlet Channel Prot. outlet Overbank outlet Outlet riser Defining Enhanced Methodology

Continuous Simulation Analyses Performed to Ascertain Performance Hydrologic Processes SWMM Representation runoff precipitation evapotranspiration infiltration BMP Development area Precipitation (hourly) Surface runoff hydrograph ET Infiltration GW recharge ET Impervious areas (runoff block) Precipitation (hourly) Stormwater runoff hydrograph BMP (Storage treatment block) Outflow hydrograph (to receiving waters) Pervious areas (runoff block) Disconnected runoff Base flows (not considered for Burgundy Rose) Hydrologic Processes SWMM Representation runoff precipitation evapotranspiration infiltration BMP Development area runoff precipitation evapotranspiration infiltration BMP Development area Precipitation (hourly) Surface runoff hydrograph ET Infiltration GW recharge ET Impervious areas (runoff block) Precipitation (hourly) Stormwater runoff hydrograph BMP (Storage treatment block) Outflow hydrograph (to receiving waters) Pervious areas (runoff block) Disconnected runoff Base flows (not considered for Burgundy Rose) Precipitation (hourly) Surface runoff hydrograph ET Infiltration GW recharge ET Impervious areas (runoff block) Precipitation (hourly) Stormwater runoff hydrograph BMP (Storage treatment block) Outflow hydrograph (to receiving waters) Pervious areas (runoff block) Disconnected runoff Base flows (not considered for Burgundy Rose)

Current design standard (WQv = 1.35 ac-ft) 1-year 24-hour (WQv = 5.33 ac-ft) 2-year 24-hour (WQv = 8.08 ac-ft) Wet Extended Detention Pond (Particulate Phosphorous Treatment)

Extended Detention Pond Impervious Pervious

Infiltration Systems Impervious Pervious

1 year-24 hour Sizing Method estimated to achieve > 80% treatment for both storage and flow through systems. Decreasing marginal gain in treatment performance as WQv size increases Results in –Alternative that modifies WQv sizing –Use of TR-55/TR-20 methods –Incorporate physical characteristics of the site Recommendation

Performance Goals: source control Goal 1 - Reduce runoff volumes to the maximum extent practicable –Hydrologic Source Control –Evapotranspiration –Infiltration Infiltration Requirement –Infiltration credit –Incorporate soil in sizing –Site evaluation Percentage of Impervious area routed through BSD Hydrologic Soil Group % Impervious area A30% B20% C10% D 5%

Performance Goals: source control Evaluation Requirements –Imp. area disconnection –Standard Infiltration –Better Site Design – Low Impact Development – Green infrastructure –Sustainable Ecosystem

Better Site Design Preserve undisturbed areas Conservation Design An approach to development design that seeks to:

Better Site Design Reduce impervious cover  Roads  Parking lots  Driveways An approach to development design that seeks to:

Better Site Design Use pervious areas for stormwater treatment An approach to development design that seeks to:

Performance Goals: source control Post Construction –Increased Curve Number –Soil Decompaction Deep Ripping Decompaction Resources

Goal 2 - Achieve less than 15% effective treatment bypass of the long term runoff volume. –Focus on hydraulic control –Capture and treatment –Bypass Simulated hydraulic function in SWMM Applied design in TR-55, TR-20 Performance Goals: sizing criteria

Sizing Criteria Sizing Criteria for Enhanced Phosphorus Removal Water Quality (WQ v ) WQ v = estimated runoff volume (acre-feet) resulting from the 1-year, 24-hour design storm over the post development watershed Evaluate and implement hydrologic source control where feasible Quantity Controls (Cpv, Q p, Q f ) Refer to existing requirements

Application Precipitation Data –Source of Isographs of Design Storms TP-40 North East Climate Center Atlas of Precipitation Extremes –Storm distribution Examples –Storage –Flow through –BSD

Good Drainage Paradigm Conventional Site Design Collect Concentrate Convey Centralized Control Credit: HWG Rain Garden Treatment Train Approach Bioretention Cell Storm Drain System Bioretention Cell Flow Path Grass Swale Grass Filter Strip Credit: HWG

Quantity Controls Channel Protection –24 hour detention of 1 year, 24 hr storm Integrated in extended detention systems Need additional storage in flow through systems. Flood Control –10 & 100 year control not exceeding pre construction peak discharge.

Goal 3 – median effluent concentration of particulate phosphorus shall be at or below 0.1 mg/L Goal 4 - median effluent concentration of dissolved phosphorus shall be at or below 0.06 mg/L –Effluent quality of the discharge –International Stormwater BMP Database –Research by Pitt, et al. (NSWQ Database) ms4/Paper/Mainms4paper.html Performance Goals: performance criteria

Performance Specifications: design details not specified in this section shall, at minimum, meet spec. in Chapter 6 –Practice options –Design geometry –media specification –optimum vegetative cover –Maintenance

Summary An effective and technically defensible criteria to address stormwater design standards in P-limited watersheds consistent with NYCDEP requirements –1 year-24 hour Sizing Method estimated to achieve > 80% treatment for both storage and flow through systems. –Effluent concentration criteria –Hydrologic source control Better Site Design Infiltration requirement –Improved design specifications –TR-55 calculation method –Update precipitation values

Questions? Shohreh Karimipour, P.E. (518)