Galvanizing Gowanus: A Policy and Process-based Study toward Net Zero CSO

School of Architecture | Graduate Center for Planning and the Environment •
Students | Aishwarya Mukund •
Faculty | Leonel Lima Ponce

This Spring 2021 SES Capstone project supports Gowanus Canal Conservancy’s goal of net-zero combined sewer overflow (CSO) into the canal. This project’s core concepts are to analyze the environmental impacts of increased population on sewage systems and assess associated neighborhood development policies. Additional hydrologic modeling was done to propose nature-based solutions for CSO mitigation. GCC’s positions on the rezoning were not reflected in the results, and the study is meant for evaluation and usage.

Designated a Superfund by the US EPA, the Gowanus Canal is an industrial waterway located in South Brooklyn. Years of unregulated development led to the impaired waterway, and the areas surrounding the Canal are still zoned for industrial uses. The US EPA is in the process of remediating the polluted canal.
The study area is now being rezoned to accommodate 45,000 residents in areas abutting the Canal. Existing city water and sewer infrastructure is inadequate. During rainy weather, wastewater and stormwater discharges directly into the Canal through combined sewer outfalls. Rain events of 1.2 inches and higher causes combined sewer overflow.
Impacts of the proposed rezoning on the City’s water and sewer infrastructure were studied using standard analytical frameworks from the CEQR Technical Manual. Related stormwater management policies were studied, and the Gowanus Neighborhood Plan’s potential for Net-Zero combined sewer overflow was analyzed. Alternative stormwater management practices were then considered through spatial analysis.
City Environmental Quality Review (CEQR) requires an impact study of zoning actions on the City’s water and sewer infrastructure, increase in wastewater and stormwater managed through related policies. In the Gowanus Neighborhood Plan, NYC DEP’s Unified Stormwater Rule requires sites over 20,000 square feet to manage stormwater equal or over 1.5 inches.
Rezoning would require streetscape improvement implementation in the neighborhood through street trees, and activate the City’s Waterfront Access Plan. The study found that the Gowanus Neighborhood Plan will not achieve net-zero increase in combined sewer overflow (CSO) in storms of 1.2 inches and higher.
The project proposes innovative ways to achieve net-zero CSO increase using landscape and hydrological modeling and the implementation of nature-based solutions. Sidewalks are assessed for historical and hydrological criteria to define locations for integrated water management pilots and programming for residents, resulting in a strong waterway that can be restored to its former splendor.