Controlling combined sewer overflows

Targeting green infrastructure for pollution reduction

Bowery Bay off the East River in Queens is a densely developed area, with LaGuardia Airport of its south and east side. There are very few unpaved or green areas, causing stormwater runoff from impervious surfaces. As part of a broader effort to control combined sewer overflows (CSOs) in New York City and to specifically reduce the amount of pollutant entering the bay, the area was targeted for green infrastructure.

Innovative approaches to stormwater management

We were assigned approximately 240ha within the tributary drainage area of Bowery Bay and tasked with the site selection and design of green infrastructure to capture precipitation and return it to the soil before it causes flooding or overflowing sewers. The site selection process involved the development of a drainage area analysis, identification of preliminary locations, and geotechnical investigation and surveying of approved sites. The design phase included the delivery of plans and bidding documents for a combination of right-of-way bioswales and stormwater green streets.

Improving water quality and reducing CSOs

The project goal is to reduce CSOs and improve the quality of receiving water bodies, while removing CSO runoff from the sewer system through detention, retention, infiltration, and evapotranspiration. Reducing discharges to the city’s sewers and waterways lessens the flow load to wastewater treatment plants and protects the waterway ecosystem. The main source of pollutants in urban watersheds is typically stormwater runoff. Green infrastructure is a resilient and low-energy approach to the reduction of combined sewer overflows.

New York City’s ongoing green infrastructure programme is reducing demand on sewer systems, improving air quality and creating a cleaner, more attractive urban environment - improving the quality of life for the whole community.