Stormwater generally is an unpleasant topic in New York City. During extreme weather events, it floods sewers causing them to overflow. The wastewater that escapes turns the city’s waterways into a cesspool and spreads a gagging stench through the streets.

These sewer overflows are the city’s biggest water quality problem and a major reason that waterways such as Gowanas, Newtown Creek, and Flushing Bay do not meet federal standards for swimming and marine wild life habitats.

However, under a bold new green infrastructure plan that includes $2.9 billion in new gray infrastructure and $2.4 billion in green infrastructure that won approval from the New York State Department of Environmental Conservation in March, the city is hoping to capture much of its stormwater with green roofs and blue roofs as well as new types of plant beds and tree pits along its streets called bioswales.

“Stormwater has always been treated essentially as a waste product—you had to get it offsite as quickly as possible,” said City Parks Department Director of Green Infrastructure Nette Compton, “By switching to green infrastructure that water is now being treated as a resource, as something that improves the function of planted areas and the aesthetic appeal of neighborhoods.”

In addition, to reducing stormwater and beautifying the city, the 18-year plan is expected to save $1.4 billion in costs for gray infrastructure that would otherwise need to be built, such as holding tanks and sewage treatment plant expansions.

To give the city time to build out its new green stormwater management system and to determine its effectiveness, the state also is allowing the deferral of decisions on whether or not a further $2 billion gray infrastructure will be necessary for two priority watershed areas: Newtown Creek and Flushing Bay.

The city’s Department of Environmental Protection (DEP) is jumpstarting the plan with three separate Requests for Proposals (RFPs), worth a total of $12 million for the design and engineering of cost-effective green infrastructure on city streets and city-owned buildings in Gowanus Canal, Flushing Bay, and Newtown Creek.

Pilot projects for the type of work DEP is seeking have already been built or are under construction. One is an “enhanced” tree pit on Autumn Avenue in Brooklyn that involves a curb cut that diverts water into the pit, where specially engineered soils and native plant species are used to absorb and filter pollutants. Another is a project at P.S. 118 in Queens that involves the study of green roofs and blue roofs which are non-vegetated source controls that slow stormwater runoff with weirs and drain outlets.

Last year, the DEP awarded $3.8 million in grants for 15 community-based stormwater projects under its Green Infrastructure Grant Program that went to private property owners and to non-profit groups for bioswales, blue roofs, green roofs, and porous pavement on private property and in sidewalks. This year the program is awarding up to $5 million.

The City Parks Department also has been designing infrastructure to help control stormwater in parks under its new High Performance Landscape Guidelines and as part of the city’s Green Streets program. Within the next two months, the agency plans to have completed 26 specially designed Stormwater Greenstreets—initiated in 2010—that feature curb cuts, trench drains, and planted  “bumpouts,” which create a new curb line some distance from the existing one to capture runoff.

The landscaped bumpouts are an example of the manifold benefits to the green infrastructure initiative, said Compton. “One of the nice things is that they are not only capturing stormwater runoff,” she said, “but they also help make intersections safer.”