Review of the New York City Watershed Protection Program (2020) / Chapter Skim
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9 Stormwater Programs
9 Stormwater Programs
Pages 249-260
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From page 249... ...
PROGRAM DESCRIPTION Stormwater treatment is accomplished through the installation of stormwater control measures (SCMs) such as detention, retention, and bioretention ponds and grassy swales, as well as more recent green infrastructure, which incorporates SCMs into landscaped urban developments including rain gardens and green roofs (NRC, 2009; NYC DEP, 2010a)
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From page 250... ...
The two general SPDES permits issued by NYS DEC and relevant to protecting the NYC water supply are GP-0-15-003 and GP-0-15-002 -- permits for Phase II MS4s and construction site activities, respectively. As part of the SPDES GP-0-15-003 permit, MS4s must reduce pollutants in stormwater discharges to the maximum extent practicable through six minimum control measures.
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From page 251... ...
Stormwater Program Retrofits Because many EOH and WOH urban areas were developed prior to promulgation of the stormwater regulations, improvements to stormwater drainage infrastructure, termed retrofits, have been needed to reduce pollutant loadings to meet FAD requirements. Retrofits have been constructed through three distinct NYC DEP-managed programs: (1)
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From page 252... ...
NYC DEP will pay an additional $22 million to the EOHWC to continue constructing stormwater retrofits in basins in the EOH watershed over the next five to six years, equating to approximately $3.5 million per year. In the WOH watershed, NYC DEP expenditures for the Future Stormwater Control Program have totaled $36.4 million to date since the 1997 MOA (NYC DEP, 2019)
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From page 253... ...
PROGRAM EVALUATION Although the Stormwater Program is largely administered according to federal and state regulations, a number of activities would improve the Stormwater Program. These efforts could include confirming SCM performance standards through storm event-based monitoring, and water quality assessments made at the catchment scale through targeted monitoring and modeling.
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From page 254... ...
254 Review of the New York City Watershed Protection Program FIGURE 9-2 Influent and effluent statistics from the International Stormwater BMP Database for 12 different SCM categories for total suspended solids and total phosphorus. Boxplots represent the 25th, 50th, and 75th percentiles, solid lines below and above the box are the 5th and 95th percentiles, and open circles and squares below and above the lines are considered statistical outliers.
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From page 255... ...
SWMM is used to determine SCM effectiveness to meet stormwater management objectives such as reducing runoff through infiltration and retention. With appropriately collected water quality and flow data, a calibrated and verified SWMM in selected catchments could be applied to unmonitored catchments to estimate pollutant loading reductions from SCMs.
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From page 256... ...
The basic study design used for the Kensico Reservoir modeling effort could be applied in designated areas with a high population density or commercial/industrial activity. Potential Impacts to Stormwater Program from Climate Change As discussed in Chapter 4, the northeastern United States is expected to experience shorter winters, higher annual average air temperatures, and more frequent extreme heat and precipitation events n the future (Porter et al., 2015; Pradhanang et al., 2013)
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From page 257... ...
Another study design would involve collecting water quality data over an extended period, with sample collections before and after installation of SCM retrofits and construction of new SCMs, in order to complete a statistically valid trend analysis. Water quality data collected at new catchment locations should be used to calibrate watershed models to support the Stormwater Program.
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From page 258... ...
2009. SUSTAIN - A Framework for Placement of Best Manage ment Practices in Urban Watersheds to Protect Water Quality.
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From page 259... ...
2000. National Pollutant Removal Database for Stormwater Treatment Practices, 2nd Edition.
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