The underground detention basin located between Court and Vine Streets on the north side of NW 3rd Street is roughly 300 feet by 150 feet and is approximately 1,400 feet northeast of the Ohio River. The basin will be the outlet point for a combined sewer separation project serving approximately 26 acres of fully developed urban watershed. As designed, this project will prevent from 0.9 MG to 1.1 MG of stormwater from entering the combined sewer system in any rainfall event. This basin will reduce peak discharges for the EPA Model year, and the 10-year and 25-year rainfall events by 90%.
By designing a 4-stage outlet system that incorporates percolation/exfiltration and direct discharge, the recovery time for the basin to drain down – that is to fully empty itself – and be ready to receive a second significant rain event is less than 12 hours. This approach saved the project over $350,000 by not requiring the complex actuated control valves and SCADA links other projects in the City needed for implementation.
Two custom-built trash and sediment traps will capture 100% of all floatable debris and 90% of suspended solids prior to flows entering the chamber system. The normal chamber sediment collection traps will then act as a secondary filter to capture any remaining sediments. These steps will significantly extend the life of the chambers and allow simplified maintenance to be performed at two access points.
