Dehart CSO Storage

The project was a necessary part of the City’s approved combined sewer overflow (CSO) long-term control plan (LTCP) to significantly reduce wet weather overflow events at CSO Outfall No. 003 located near the intersection of Dehart Street and River Road and is the final CSO in the collection system to be addressed under the City’s LTCP. To determine the volume of storage required, an XP-SWMM hydraulic model was calibrated utilizing flow metering data. The project included approximately 1,000 feet of a 15’x15’ concrete tunnel in River Road from Dehart Street to Happy Hollow Road to provide a peak wet weather storage of 1.7 million gallons of combined sewage that would have otherwise overflowed to the Wabash River. The stored flow is pumped back into the sewer system for conveyance and treatment at the Water Resource Recovery Facility.

City officials utilized the GSC method of procurement. Wessler staff worked closely with the GSC contractor during 60% and 90% design, conducting value engineering workshops to modify the design to improve constructability and reduce construction cost. Dual 12-foot diameter precast concrete pipes were initially designed, but after value engineering a 15’x15’ concrete tunnel was selected as the cost-effective alternative due to the limited space for construction within the right-of-way of River Road.