Earlier this month, New York City Mayor Michael Bloomberg honored Carmel Valley green roof gurus Rana Creek for their work on North America’s largest continuous green roof.

Perched atop the underground Croton Water Filtration Plant in Bronx, N.Y., the roof was one of 10 projects to receive the New York Public Design Commission’s Excellence in Design award. The project will be completed in 2012 in partnership with Grimshaw Architects, the international firm that is designing the water treatment plant.

The green roof combines infrastructure with pleasure, according to Project Manager Raphael Garcia. “The main goal for the design was to facilitate the needs of the area, which was [to maintain it as] a golf course driving range,” he says. “We created a low-water driving range with organic fertilizers. There will be vehicular traffic [from golf carts and maintenance machines] over the driving range, so the design is resilient and drought-tolerant. Runoff from the driving range is also minimized from the use of organic fertilizer.”

While it provides a recreational space—as well as native plant habitat, insulation for the water treatment plant, and vegetative pre-treatment for runoff into the Brooklyn River—the roof serves another vital role for the water treatment plant.

“One third of Manhattan’s water supply goes through this plant in the Bronx,” says Jeff Condit, strategy and development manager at Rana Creek. “That makes it a homeland security target. So they put it underground and covered it with this green roof. You won’t even know this water treatment plant is going to be there.”

The roof will cover nine acres when finished, nearly doubling the Ford Assembly Plant green roof in Dearborn, Mich., which is currently the largest green roof on the continent.

The Croton Water Filtration Plant is to be constructed partly from recycled materials, and its aboveground facilities will be LEED gold-certified. The project, like its fellow award winners, was chosen for its adherence with PlaNYC, New York’s long-term vision for a greener city.