Sunday, December 25, 2011

New York City Department of Environmental Protection (DEP) Proposes Enhanced On-Site Stormwater Controls for New Construction Projects to Improve Harbor Water Quality
On September 29, 2011 Environmental Protection Commissioner Carter Strickland proposed a rule requiring new construction and major building alteration projects to capture more stormwater runoff, provide additional capacity in the combined sewer system and reduce street flooding. New York City, like other older urban areas, is largely serviced by a combined sewer system where stormwater and wastewater are carried through a single pipe. During heavy storms, the system can exceed its capacity and must discharge a mix of stormwater and wastewater — called a combined sewer overflow, or CSO — into New York Harbor. Enhancing an already existing requirement, the rule will employ a wide range of on-site stormwater control techniques to all new development, redevelopment and major alterations in combined sewer areas. For a typical site over 5,000 square feet, DEP estimates that the rule will limit stormwater discharge to 10% of its present permitted flow to the combined sewer system using cost-effective detention, infiltration, and conservation techniques. This rule will lead to on-site control systems that are projected to reduce combined sewer overflows by as much as 800 million gallons over the next 20 years based on historic development trends. No existing homes or developments will be impacted by the new rule. The rule delivers a key component of the NYC Green Infrastructure Plan announced by Mayor Bloomberg last September.

"Combined sewer overflows remain one of the greatest challenges to water quality in New York Harbor," said Commissioner Strickland. "Our Green Infrastructure Plan seeks to control water at the source to keep it out of our sewers while balancing compliance costs. Through several years of outreach to the real estate, development and environmental communities, we have received many comments to adopt innovative and cost-effective techniques, and the final rule allows additional opportunities to use infiltration and recycling systems to meet control requirements."

The new proposed rule will reduce the amount of stormwater runoff discharged from new development projects as part of DEP's existing permitting processes. The current rule is based on a number of different factors such as existing sewer design criteria, property type, size, and drainage area of the lot. The new rule will reduce current limits for runoff to 10% of present permitted flows through the use of innovative control systems, such as blue roofs, green roofs, or subsurface gravel beds and stormwater chambers. For example, a typical one-acre site currently allowed to release 2.5 cubic feet per second under existing standards, will now be required to detain and release runoff at 0.25 cubic feet per second through some combination of on-site stormwater control systems. The cost impact of the new standard on a project's development is estimated to be an additional 0.3% to 1.5% of total costs.

The rule was developed through several task force meetings DEP conducted with the Mayor's Office of Long-Term Planning and Sustainability and its partners across city agencies. Over the past two years, DEP has received input from building industry which includes real estate, development and professional applicants, and environmental organizations, including the Real Estate Board of New York, the Regional Planning Association, American Institute of Architects, Buildings Sustainability Board, Citizens for Affordable Housing, US Green Buildings Council and the Green Infrastructure Steering Committee. Based on extensive feedback, the rule credits infiltration into soil and recycling for on-site use, which can reduce the size of stormwater control systems.

To assist with the implementation of the new rule, DEP will release a companion document, Guidelines for the Design and Construction of Stormwater Management Systems, offering guidance to the development community and applicants with the selection, planning, design and construction of on-site stormwater detention systems. The manual was developed in consultation with the Department of Buildings, and will feature guidance on siting, design and construction considerations for various stormwater control systems, as well as operation and maintenance recommendations. The guidelines will be continually updated to reflect the latest technology and best practices.

New York City Department of Environmental Protection (DEP)
September 29, 2011

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