At the foot of Second Street in Brooklyn, hard by the Gowanus Canal, is a tiny green space with a very big job.
Aptly called Sponge Park, the 2,100-square-foot plot will, when it opens next spring, intercept thousands of gallons of storm water, along with pollutants like heavy metals and dog waste, before they can enter the canal. The park’s absorbent qualities come from flood-tolerant plantings like asters, Rosa rugosa and sedge grass, as well as a network of sand beds and soils designed to hold water.
The park is part of a larger effort in New York City and urban areas across the country to prevent polluted storm water from flowing directly into rivers or overloading sewage treatment plants. With combined storm-sewer systems like New York’s, in which one set of pipes handles both sewage and storm water, even moderate rainfall can overwhelm treatment plants, causing raw sewage to spew into waterways.
Each year across the city, nearly 30 billion gallons of raw sewage and polluted storm water are discharged from hundreds of pipes into local waterways when sewage plants are overwhelmed. Such overflows can occur up to 75 times a year, according to the environmental group the Natural Resources Defense Council, and are the most serious challenge to water quality in the New York area, preventing rivers and bays from meeting federal standards for swimming, fishing and wildlife habitats.
The city’s environmental agency is now in the midst of a 20-year, $2.4 billion campaign, using public and private money, to protect local waterways with a network that relies on ecology.
In addition to using traditional, so-called gray infrastructure like holding tanks and tunnels, the program deploys green roofs, gardens, special soils and porous surfaces to capture and retain storm-water runoff — often through landscapes such as curbside gardens and playgrounds.
It is an approach gaining momentum across the United States, where 860 municipalities have combined sewer systems, according to Adrian Benepe, the senior vice president and director of city park development at the Trust for Public Land, a nonprofit conservation group.
In New York City, the trust has overseen the construction of seven playgrounds designed to capture storm water, out of 40 that are planned, and it will develop nearly 40 playgrounds in Philadelphia. The group is also involved in several other green infrastructure projects, from Los Angeles to Boston. –(December 2015) by Lisa Foderero in the New York Times.