New York City agreement to reduce CSO

May 2012, Vol. 67 No. 5

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.