Working within the site constraints, we developed a conceptual design that allows floodwater to be collected and to infiltrate into the existing subsurface. The proposed project’s effectiveness was tested using the Infoworks ICM model, which provided flood depths to compare with existing conditions. The difference in flood depths and extents formed the basis of benefit-cost analysis (BCA) that was performed using FEMA’s BCA program.

Four subsurface detention and retention technologies were evaluated for the project’s design. A subsurface storage module technology was selected as the most effective to satisfy stormwater management design criteria within the limited space in each of the six practice locations identified. The system includes integrated above-ground and below-ground storage for extreme storms. An innovative aspect of the design included a water square within the newly sunken basketball court in the North Clinton Houses Campus to provide additional above-ground emergency storage during extreme cloudburst rainfall events. The North Clinton campus stormwater redesign plan includes three cloudburst management practices, 1.58 acres of contributing drainage area, and approximately 130,000 gallons of rainfall volume capacity. The South Clinton campus stormwater redesign includes three cloudburst management practices, 1.66 acres of contributing drainage area, and approximately 165,000 gallons of rainfall volume capacity.

The project is a strong example of cloudburst management, which uses a combination of grey and green infrastructure as a way of absorbing, storing, and transferring stormwater to minimize flooding from heavy rain events. It is funded by the FEMA Hazard Mitigation Grant Program’s (HMGP) Advance Assistance program and was submitted for FEMA Building Resilient Infrastructure and Communities (BRIC) funding. Our firm provided feasibility studies, hydrologic and hydraulic modeling, and engineering designs services for the project. Additionally, our firm provided community engagement services, including holding focus groups and presenting at programming events, and developed a new website for NYCHA.