IMPLEMENTATION OF AN OFFLINE STORAGE FACILITY IN WASHINGTON SUBURBAN SANITARY COMMISSION'S DYNAMIC HYDRAULIC SEWER SYSTEM MODEL

This technical paper outlines the approach followed to implement an offline storage facility in a baseline dynamic hydraulic sewer model for Washington Sanitary Suburban Commission's (WSSC) Rock Creek Sewer Basin sanitary sewer system using Wallingford's InfoWorks CS program. The sewer system model was developed to meet the requirements of the WSSC Sanitary Sewer Overflow Consent Decree and assesses the existing and long-term capacity of the sanitary sewer system and offline storage facility of the Rock Creek Basin.The Rock Creek Storage Facility allows WSSC to limit peak discharges at the basin boundary to an agreed limit during wet weather events. The hydraulic model was used to simulate the current operational procedures and alternative scenarios for the operation of the storage facility. The results show that the current operational procedures are effective in limiting the flows at the basin boundary though they may result in using the facility more frequently than necessary and filling the available storage volume early during a storm event causing the storage to be unavailable for subsequent storm events. The modeling of alternative operational scenarios described in this paper resulted in refined procedures that improve the operation of the storage facility. This work was performed to demonstrate how the model could potentially be used to refine system operations. WSSC has not implemented these procedures.