Hydraulic Modeling for the Evans Street CSO Relocation
Greeley and Hansen, A TYLin Company, built, calibrated and validated a hydraulic model for the McKeesport combined sewer system to evaluate capital project investments.
The Evans Street hydraulic model allowed the Pennsylvania American Water Company (PAWC) to identify and address any capacity issues associated with ongoing U.S. Army Corps of Engineers (USACE) projects to construct new locks and dams. Construction of these will raise the upstream water surface elevation at McKeesport by 2 feet. The existing systems combined sewer outfall will be completely submerged, constricting flow through the upstream collection system and overflow. PAWC requested Greeley and Hansen’s assistance in advising and supporting a flow monitoring program designed to identify capacity issues in the McKeesport, PA combined sewer system.
The McKeesport system discharges to the Monongahela River which may experience a reduction in flow capacity due to the higher water surface elevation. The first step in understanding the impacts of the USACE work was the flow monitoring program. Greeley and Hansen advised PAWC on the flow monitoring and existing conditions monitoring program to ensure the data would be useful in developing an accurate and reliable hydraulic model. The second step is to construct the hydrology and hydraulic model from existing conditions data and calibrate the model using the collected flow monitoring data. After the model was constructed and run, Greeley and Hansen identified the most restrictive flow scenarios which could result in surcharging, bottlenecks and blockages which would reduce overall system capacity. The Greeley and Hansen team ultimately determined that the increased water surface elevation in the receiving waters would reduce overall capacity in the collection system but would not cause upstream flooding. This model allowed for PAWC to avoid a multi-million dollar pipeline relocation project and provided them with reliable backup information in their discussions with regulatory agencies.
Project Highlights:
- Flow monitoring program designed to identify capacity issues
- Hydrology and hydraulic modelling
- Savings of multi-million dollars in unnecessary capital projects