New York City agreement to reduce CSO

In a landmark agreement on an enforcement Order to improve the overall water quality in New York Harbor waters, the New York State Department of Environmental Conservation and New York City Department of Environmental Protection announced the city will invest approximately $187 million over the next three years and an estimated $2.4 billion of public and private funding over the next 18 years to install green infrastructure technologies to manage stormwater before it enters the city’s combined sewer system.

The city maintains the flexibility to prioritize green investments in areas of the City that will benefit most from the resulting reductions in combined sewer overflows (CSOs).

“It is now an official green light for the groundbreaking NYC Green Infrastructure Plan,” said New York City Environmental Protection Commissioner Carter Strickland. “This multi-pronged approach strikes the perfect balance to meeting the goal of improving the water quality of New York Harbor: gray infrastructure where it is still cost effective and cutting-edge green technologies that not only absorb the water where it lands, but enhance the local quality of life by providing shade and beautifying the city. This agreement, which will be implemented in partnership with numerous city agencies and environmental stakeholders, truly represents a breakthrough in how we re-envision stormwater management…”

New York City, like other older urban communities, is largely serviced by a combined sewer system where stormwater and wastewater are carried through a single system. During heavy storms, the system often reaches capacity and must discharge a mix of stormwater and wastewater, called a combined sewer overflow, into New York waterbodies. If the overflows were not discharged, the city’s wastewater treatment plants would be flooded and unable to treat wastewater.

Through a mix of cost-effective gray infrastructure and cutting-edge green infrastructure, the agreement aims to significantly reduce sewer overflows into waterways through a combination of traditional and green infrastructure practices over the next 18 years. The city estimates that approximately 1.5 billion gallons of CSO flows will be removed annually by 2030 through the application of green infrastructure. Green infrastructure, such as green roofs and porous pavement, improves harbor water quality by capturing and holding stormwater runoff before it enters the sewer system and contributes to CSOs.

As part of the agreement, the state and city have resolved all outstanding compliance issues associated with the Consent Order. The modified Consent Order requires the city to complete $1.4 billion in cost-effective gray infrastructure substitution projects to improve the city’s collection system performance. These substitute projects will save the city taxpayers $1.4 billion from the original tanks and treatment plant expansions, required by the Consent Order, while providing equivalent water quality benefits.

Examples of green infrastructure projects include: blue roofs and green roofs, which use mechanical devices or vegetation to slow roof water from draining too quickly and overwhelming sewers; porous pavement for parking lots that allows water to seep through it and be absorbed into the ground rather than running-off into the sewer system; tree pits and street side swales for roadways that allow water to pool in underground holding areas until it can dissipate in the ground or transpire through plants; wetlands and swales for parks; and rain barrels in some residential areas.

In connection with the agreement, the DEP has issued a RFP for engineering and design services contracts to develop green infrastructure master plans in three of the city’s combined-sewer areas and in other CSO areas of New York. The DEP expects to award the first RFP response contracts by the summer, with design work to start immediately after.

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