Client: City of Indianapolis

Location: Indianapolis, Indiana

As part of its five-year comprehensive plan to improve the water quality of its streams, the City of Indianapolis needed to reduce combined sewer overflows (CSOs) at CSO Outfall 039, which discharged into the White River. Donohue designed the new facility including a 3-mg underground storage/primary treatment tank, a flow control structure, submersible lift station with 7200 gallons per minute (gpm) duplex pumping system, flow monitoring equipment, tank flushing system for odor control, and associated piping. Donohue also designed bank stabilization around the new facilities, an access road, power distribution, and provided permitting assistance.

The cast-in-place concrete tank was constructed completely below grade in the flood plain of the White River. Auger-cast in-place piles were primarily used to resist the uplift that occurs when the river floods over the top of the tank. The storage/primary treatment tank has six submersible pumps for conveyance of captured flow back into the interceptor and is then sent to the wastewater treatment plant for complete treatment. The pumps have grinder heads capable of passing large solids and an access hatch was provided above the pumps for pump removal while the tanks are full. The tank was designed to be expandable to 10 million gallons and allow for the addition of UV disinfection.

Encompassed in a park-like recreational area, design considerations included aesthetic features to blend in the visible facilities (electrical and control building) into its surroundings.

This project received an Honor Award in the ACEC Indiana Engineering Excellence competition and was a National Finalist.