Nature-based solutions: Restoring life to a polluted waterway

Our role included drainage analysis across more than 210ha and identifying the best sites for green infrastructure.

Opportunity

Newtown Creek in New York was once one of the most polluted industrial sites in the US. The country’s first kerosene refinery was established there in 1854 and the first modern oil refinery in 1867. Sugar refineries, tanneries, canning plants, and copper wire factories followed. The creek, a 6km tributary of the East River, was eventually enlarged and bulkheaded, and it became a major shipping hub. In addition to decades of legacy pollution from industrialisation, stormwater runoff and wastewater pour into the creak from combined sewer overflows (CSO), adding to contamination. Polluted sludge, 4.5m deep, eventually covered the creek bed and in 2010 it was declared a Superfund site, a federal programme to investigate and clean-up areas contaminated with hazardous substances.

Solution

The New York City Department of Environmental Protection (DEP) manages the city’s water supply, and we supported the agency to implement nature-based solutions to significantly reduce the amount of stormwater reaching the combined sewer system each year and help Newtown Creek to recover. Our role included drainage analysis across more than 210ha and identifying the best sites for green infrastructure. Bioswales – vegetated, shallow, landscaped depressions – were installed to capture rainwater runoff that would otherwise have entered combined sewers, allowing it to infiltrate the soil and be absorbed by the vegetation. The bioswales were excavated to a depth of 1.5m and backfilled with stone and engineered, with voids able to store stormwater and promote infiltration. Impervious surfaces were also replaced with permeable substrate, organic topsoil, and vegetation.

Outcome

Life is returning to the creek. Across the CSO tributary, the amount of polluted runoff reaching the sewers has fallen, street flooding is less common, water quality has improved, trees and other vegetation have reduced air pollution and alleviated the urban heat island effect as well as making the area more attractive for those who live and work there. In the residential and commercial neighbourhoods of Bushwick, a highly urbanised community in Brooklyn, 19 bioswales and stormwater green streets prevent more than 300,000 litres of stormwater from reaching the sewer system each year. The installation of the green infrastructure systems has also alleviated pressure on the city’s grey infrastructure needs, helping to reduce capital costs. DEP has made funding available to maintain the bioswales.