Operated by the city’s Water and Sewer Department, the sewer system in O’Fallon, MO, includes a vast collection system and full scale, state-of-the-art regional wastewater treatment plant with a capacity of 15 million gallons per day. It is complete with three equalization basins, a Class A bio-solids dewatering and handling facility, 17 wastewater pumping stations and large capacity interceptor sewers ranging up to 48 in in diameter. The collection system consists of more than 200 miles of interceptor and collector lines with a little more than 6,000 manholes.
Originally constructed in 1984, the O’Fallon Wastewater Treatment Plant was to undergo upgrades and additions in 2020. Included in the proposal was the construction of a new, 48,675 sq-ft Biological Nutrient Removal (BNR) Tank, a 407 sq-ft Splitter box, a new High Flow Discharge Pump Station, a new blower building, and upgrades to the existing clarification process. Other proposed updates would include: Ancillary site piping to tie the new systems into the overall treatment train; a new cascade aerator; improvements to the plant outfall. Menard USA was contracted to provide ground improvement to support the construction of the BNR Tank and a Splitter box situated on compressible and liquefiable layers. The selected techniques were Controlled Modulus Column (CMC)® rigid inclusions and earthquake (EQ) drains.