As part of the City of Fort Smith’s ongoing regulatory negotiations to eliminate wet weather sanitary sewer overflows, the Mill Creek Pump Station was identified for a large scale capacity expansion and equalization storage. The capacity expansion of the pumping station included the construction of a new Electrical Building and a self-cleaning, trench style wet well pump station with five submersible pumps and two mechanical bar screens. The rated pumping capacity of the new Mill Creek Pump Station is 32 million gallons per day (MGD) which includes both dry and wet weather pumping capabilities. The new pumping station increased the peak wet weather to the P Street Wastewater Treatment Plant from 10 MGD to 16 MGD. The equalization storage for the project was obtained by constructing a 3.5-million gallon precast, prestressed, concrete Equalization Tank for temporary peak flow storage.
The biggest challenge for the Project was the construction of a new pumping station that was approximately 45-feet deep on the relatively small Mill Creek Pump Station site while maintaining the existing station in operation. The pump station excavation and construction was achieved through the use of a shoring system that included temporary steel solider piles, internal whalers, transverse struts, and timber lagging. Hawkins-Weir Engineers in association with CDM Smith designed Mill Creek Pump Station and Equalization Tank Project and Hawkins-Weir provided the lead role during construction.