The City of Rock Island needed assistance preparing and negotiating a long-term control plan to control discharges from combined sewer overflows (CSOs) and meet the requirements of the U.S. Environmental Protection Agency consent decree to resolve discharge violations. Mead & Hunt performed a sewer system evaluation, collection system flow and water quality monitoring, rainfall monitoring, and calculated radar rainfall estimates by sewershed. With assistance from our team, the city metered 27 sites to characterize flows of all major sub-basins draining to the municipal wastewater treatment plant. Metering data confirmed a linear relationship between rainfall and runoff, typical of CSOs. Our team then developed, calibrated, and validated a system model using PCSWMM hydrologic and hydraulic modeling. PCSWMM is an advanced modeling software for stormwater, wastewater, watershed and water distribution systems. The model replicated a 95% mean confidence limit compared to metered rainfall-runoff response. This unique approach provides statistical confidence that the chosen CSO control alternatives will be effective for a variety of precipitation events. Based on this model and analysis, the city was successful in preparing and negotiating its plan.
Rock Island Stormwater Management
- CLIENT: The City of Rock Island
- LOCATION: Rock Island, IL
