By Sophie Quinton on Oct 15, 2010

Green and Blue Coming to a Rooftop Near You

Although New York’s creaky wastewater treatment systems have improved in recent years, it still struggles to deal with the sheet volume of water that a storm can send shooting off city roofs, down streets and over parking lots.

By simply improving vegetation and enacting green building codes, New York could achieve a goal of reducing runoff by 40 percent by 2030 and save taxpayers $2.4 billion in the process. Photo: Flickr/wendy

The city government has proposed an unconventional solution: Green rooftops, better landscaping and porous pavements may be coming to a neighborhood near you.

The proposed Green Infrastructure plan would reduce runoff, while simultaneously reducing urban heat island effect and raising property values – and would do it all at a low cost. By simply improving vegetation and enacting green building codes, New York could achieve a goal of reducing combined sewer overflows by 40 percent by 2030 and save taxpayers $2.4 billion in the process.

The plan would rely on a combination of green roofs, porous parking lots, and vegetation along sidewalks to help absorb rainwater. Because plants naturally absorb water, they prevent flooding and stop runoff from reaching—and overwhelming—wastewater treatment systems.

Rooftop solutions are a major feature of the plan. The plan promotes both blue roofs, which divert rainwater by mechanical means, and green roofs, a layer of vegetation that can be installed on flat surfaces.

Of the two options, green roofs deliver more benefits. The vegetation helps retain water, reduces urban heat island effect, and reduces both carbon emissions and utility bills.

The layer of plants acts like a layer of insulation, reducing the need to cool and heat the building. In other cities, the installation of green roofs on just 10 percent of buildings has reduced runoff by 2.7 percent for the region and 54 percent for each individual building, according to the NYC Department of Environmental Protection.

Under the Green Infrastructure plan, the city would directly implement rooftop and landscaping solutions on its own property, like schools, public high-rise residences and other municipal buildings.

New York would also impose green infrastructure requirements on new private building projects, essentially subsidizing the government plan with private funds. Residents and building occupants would benefit from lower water bills, reduced noise pollution and the higher property values that well-landscaped properties typically attract.

Like most American cities, New York has relied on expensive technical solutions to runoff control, constructing ever-larger holding tanks, tunnels and pumping systems. The city has determined that a traditional “grey infrastructure” approach to solving New York’s current crisis would cost $6.8 billion, money that would ultimately come from residential and commercial water bills. By implementing green infrastructure solutions, the city says it can achieve the same results with 30 percent less funding.

Acting in partnership with other city agencies, as well as local environmental organizes and community groups, the city government aims to address at least 10 percent of impervious areas around the city, the mayor’s office said in a statement. Mayor Bloomberg chose to announce the plan from the roof of PS 118, an elementary school in Queens and the site of a successful green roof pilot project.

The NYC Green Infrastructure proposal is still in the planning stages, and subject to all sorts of negotiation both within government agencies and between the public and private sectors. However, if the plan goes through, it could both help New York keep its waterways sludge-free, and give us all a cooler, greener city to enjoy in the process.

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