This report provides an independent study of how the stormwater management and sewer overflow problem in the Pittsburgh, Pennsylvania metropolitan region could grow with future climate, land use, or population change, and discusses potential long-term solutions using new analytical approaches developed by RAND. The analysis provides a baseline of scientific information intended to support ongoing regional coordination around stormwater management and water-quality planning.
- Simulations of the recent past suggest that sewer overflow volumes are up to 15 percent higher than previously estimated.
- Future rainfall, population, and land-use changes could increase sewer overflow volumes.
- Expanding wastewater treatment plant capacity or cleaning existing deep interceptor tunnels could represent low-regret, near-term options.
- Strategies combining treatment expansion, interceptor cleaning, and source reduction could cost-effectively reduce future overflow, but uncertainty remains high.
- None of the combined strategies tested eliminates sewer overflows.
Green stormwater infrastructure (GSI), evaluated in isolation, yields poor cost-effectiveness for overflow reduction under commonly used assumptions, but is more cost-effective in higher rainfall scenarios.