by Anna Meyer
Legacy industrial pollution, combined sewer overflows, and stormwater runoff plague the Gowanus Canal in Brooklyn, New York. The canal and its environs, designated a superfund site in 2010, may seem like a hopeless case.
Yet as land use near the canal has shifted from heavy industrial to a mix of light industrial, commercial, and residential, more and more people—and agencies—have grown interested in cleaning up the canal and minimizing further pollution, such as combined sewer overflows.
The canal’s champions include the Gowanus Canal Conservancy and Brooklyn-based design firm DLANDstudio. According to Susannah Drake, a landscape architect and founding principal of the firm, the fledgling Conservancy approached her newly formed firm in 2008 to develop a master vision for adding 5.5 acres of open space to the densely populated Gowanus Canal Watershed.
The staff at the Conservancy had liked an earlier proposal from the studio to build a public green space over part of the Brooklyn Queens Expressway as a means of reconnecting neighborhoods.
Drake says she helped the Conservancy to procure a grant from the New York State Council on the Arts to create the master plan. Andrea Parker, the Conservancy’s current executive director, says it was the group’s “first large grant.”
Drake realized that publicly owned street ends abutting the 1.8-mile-long canal could be transformed into working landscapes that absorb and filter stormwater runoff.
That idea, which she dubbed a “sponge park,” appears multiple times in the master plan. DLANDstudio’s vision was to connect twelve street-end sponge parks and other community-recreation areas with an esplanade along the canal.
The firm has received multiple awards for the 2008 master plan, including honors from the American Society of Landscape Architects and the American Institute of Architects. The sponge park design, in particular, is lauded for its two simultaneous identities: green infrastructure and public park.
In 2010, NEIWPCC awarded DLANDstudio an EPA grant of $184,995 to design a pilot sponge park. Over the next six years, DLANDstudio not only devised the pilot project but also raised funds for construction and worked with city, state, and federal agencies to see the project through to installation.
To develop the project plan, the firm worked closely with neighborhood residents, community groups, and numerous government agencies whose jurisdictions the small park intersects.
These authorities included the New York City Departments of Environmental Protection, Parks and Recreation, Transportation, City Planning, and Design and Construction, and the New York State Department of Environmental Conservation. Since the canal is a Superfund site, the EPA and the U.S. Army Corps of Engineers had regulatory jurisdiction as well.
“It is important to understand the rules and understand who has jurisdiction,” Drake says of the labyrinthine permitting process. “Visualization of territory…stops some of the churning that can happen when it’s not clear who is the responsible party.”
The pilot project cost a total of $1.5 million, but Drake credits the grant from NEIWPCC not only as critical to moving the pilot-project forward but also helping establish the firm, since it was “the first big grant” for the project.
Gowanus Canal Sponge Park officially opened in October of 2016. On the surface, the park is geometrically simple. Twin bioremediation basins flank a central walkway that connects the street to the water’s edge. The basins include a mix of green vegetation.
The park is also designed to work against two major sources of pollution to the Gowanus Canal: street runoff and combined sewer overflows. According to the design firm, the park will capture some one million gallons of stormwater annually that would have otherwise drained directly into the canal or entered the sewer system.
Instead, stormwater from the street perpendicular to the park is directed to the bioretention basins, which contain native woody plants, soil, and sand. The plants chosen absorb, accumulate, or metabolize pollutants that stormwater picks up on roadways, including oil and heavy metals. They include beach rose, bay laurel, summersweet, iris, and a grass-like plant in the sedge family.
The plants are native to the region, salt tolerant, and able to withstand various levels of inundation.
Sponge Park uses mostly woody plants instead of herbaceous plants typically found in bioremediation basins. Drake said she wanted Sponge Park to be easy to maintain and to feel like a park, even in the New York winter.
“Woody plants are used more in park landscapes,” she said. “In the winter, it looks like there’s something there.”
Some of the water infiltrates into groundwater. The remainder flows into the canal, but only after being filtered by the basins.
The system also diverts some of the rainwater from entering the sewer during small and large storms. In this way, the park helps prevent the Red Hook wastewater treatment plant in Brooklyn—which receives both domestic wastewater and stormwater—from reaching its maximum capacity discharging untreated wastewater into the canal. In 2005, the U.S. Army Corps of Engineers estimated that the eight combined sewer overflow outfalls along the canal discharge over 300 million gallons of untreated waste into the canal every year.
Residents and officials have different reasons for supporting Sponge Park, but a compelling one is how the park complements the cleanup that will happen as a result of the EPA’s 2010 designation the canal as a Superfund site. Like so many waterways in the Northeast and beyond, Gowanus Canal served as a place to dump waste for more than a century.
The canal was a major industrial shipping route, and received industrial waste from paper mills, tanneries, and chemical plants. Factories that manufactured gas from coal for lighting, cooking, and heating added their effluents to the mix. High concentrations of more than a dozen contaminants, including polycyclic aromatic hydrocarbons, polychlorinated biphenyls and heavy metals, including mercury, lead, and copper, have been found in canal sediment.
The EPA also recognizes combined sewer overflows as part of the problem. Consequently, the remedy plan for the site includes not only removal of contaminated material but also the construction of two large storage tanks that will hold wastewater from the combine sewer until treatment plants can handle it.
Another notable aspect of Sponge Park is its modular construction. The bioretention basins are made up of prefabricated perforated concrete cells. The whole park is about 2,500 square feet (about the size of a singles tennis court).
Offsite construction offered multiple benefits, according to Drake. Fabricating the cells in a controlled environment, and not onsite, meant the concrete curing process was not disrupted by tidal changes in the water table. (The Gowanus Canal was built in 1881 on a wetland connected to the New York Harbor.) In addition, offsite construction gave the firm more control of the construction quality.
The fact that the cells are identical to one another is economical. Perhaps most significantly, the pattern is now on hand, ready to cast any number of modules.
Drake says her firm is currently working with the New York City’s Departments of Transportation and Environmental Protection on a few projects that use the technology developed for Sponge Park. However, she has set her sights even higher, hoping that the modular basins will become “the Jersey barriers of stormwater management”: inexpensive, simple, and easy to deploy widely.
In a relatively recent change to City zoning, every time a parcel changes use (from industrial to residential, for example), the property owner is required to provide a forty-foot setback from any waterfronts. Subsequent regulation applied this standard to the canal.
In a few places on the canal, including a parcel adjacent to Sponge Park, the setback has made room for a section of an esplanade—a public walkway dotted with benches. Lightstone Group, the developer of a high-rise near Sponge Park, installed a small boat ramp on the esplanade so that boaters, such as members of the local canoeing group, can easily leave the water if a barge comes along.
Susannah Drake said public access to the canal was one of the main concerns raised when DLANDstudio solicited public comments about the master plan for the watershed in 2008. In 2016, when Sponge Park officially opened, New York City Council Member Stephen Levin said, “This project proves that taking care of our environment and providing amenities to the public are not mutually exclusive—in fact, quite the opposite is true. The more green infrastructure and open space we create, the greater the public’s stewardship.”
The plan includes provisions for Manhattan College to monitor the park’s effectiveness at removing pollutants. NEIWPCC’s 2010 grant to DLANDstudio covered the development of a quality assurance project plan for the monitoring work, which will include measurements of the volume of runoff entering Sponge Park and the amounts of pollutants removed. It is likely that the results of the monitoring will give confidence to those considering installing a sponge park or similar green infrastructure system.
Meanwhile, the Gowanus Canal Conservancy, which was one of many partners in the design process of the pilot project, is looking at the big picture. Andrea Parker, executive director of the Gowanus Canal Conservancy, says the group is seeking “a community vision plan for Gowanus Greenscape, the network of parks and public spaces centered on the Canal.” The Conservancy plans to post a request for proposals this spring.
Parker says the plan “will build on” the 2008 master plan “and take into account the canal’s 2010 designation as a Superfund site as well as expected zoning changes.”
Anna Meyer is an Environmental Analyst at NEIWPCC.
This story is available as a reprint, part of a series from NEIWPCC. It was originally published in the March, 2017, issue of Interstate Waters.