In order to reduce combined sewer overflows, the New York City Department of Environmental Protection’s (DEP’s) new Unified Stormwater Rule (USWR) requires newly-developed or redeveloped properties to more effectively manage stormwater on-site.
By retaining more stormwater on site, the USWR will help to keep the city’s drainage system from being overwhelmed during heavy rainstorms, which otherwise can lead to flooding, backups into homes and businesses and overflows into waterways.
Modeling projects the rule will result in the reduction of Combined Sewer Overflows citywide by approximately 360 million gallons annually by 2030, helping to further improve the health of New York Harbor.
“We have all witnessed how climate change is creating stronger and more damaging storms in New York City and this common sense update to our Rules enlists property developers in our collective effort to create a more resilient city,” said DEP Commissioner Rit Aggarwala. “Cities across the world are following our green infrastructure model where we have committed nearly $2 billion and built more than 11,000 stormwater assets and now, as properties are newly developed or redeveloped, they will include plans to retain stormwater on site to help to reduce flooding, enhance public safety and improve the health of our waterways.”
The USWR updates and aligns Chapters 31 (stormwater quantity and flow rate requirements) and 19.1 (construction/post-construction permitting program water quality requirements) of Title 15 of the Rules of the City of New York.
Under the Chapter 31 amendments, the USWR increases the amount of stormwater required to be managed on a property and further restricts the release rates for all new and redevelopment projects that require a DEP House or Site Connection Proposal.
Additionally, under the Chapter 19.1 amendments, existing requirements for areas of the city with separated sewers will expand into the areas of the city that are served by combined sewers and will now apply to sites that disturb 20,000 square feet or more of soil or create new impervious surfaces of 5,000 square feet or more.
These properties will be required to apply a green-infrastructure-first approach, employing techniques such as rain gardens, permeable pavers, and green roofs.
A new New York City Stormwater Manual accompanies the USWR to provide clear guidance on requirements and design options. The green infrastructure requirements will benefit the city by reducing combined sewer overflows and preventing polluted stormwater from discharging directly into local waterbodies.
“The Stormwater Infrastructure Matters (SWIM) Coalition applauds DEP on the Unified Stormwater Rule, which will lead to stronger protection of our waterways, as well as reduced flooding and enhanced climate resiliency for our city,” said Leonel Ponce, Chair on the SWIM Steering Committee. “SWIM looks forward to working with Commissioner Aggarwala to further strengthen measures to reduce polluted stormwater and mitigate the impact of climate change.”
In September 2020, the New York City Council passed Local Law 91 enabling DEP to move forward with the Chapter 19.1 amendments necessary to package the new USWR. Draft rules were published in 2021 and effective on February 15, 2022.
