W. M Lyles Co. joint ventured with AECOM to design and build the STI Project for the City of Davis. The upgrades to the existing 8.4 MGD wastewater treatment plant provide compliance with Title 22 requirements. The project consisted of replacing the existing oxidation pond process with an activated sludge process which included four Aeration Tanks, four 75’ diameter Secondary Clarifiers, two RAS/WAS Pump Stations, and two Scum Pump Stations. A new Blower Building with three single-stage turbo blowers provides aeration air to the Aeration Tank. The old Chlorine Contact Basin was converted into a new Primary Effluent Pump Station with four new vertical turbine solids handling pumps to transfer primary effluent to the Aeration Tank. The new solids handling facilities consists of a Dewatering Building with two screw presses, two rotary drum thickeners, thickened sludge feed pumps, and a system of sludge conveyors, a canopy covered sludge storage area, and two above grade bolted steel digested sludge storage tanks. A new Boiler Building with hot water boilers provide heat for the existing Digesters hot water loop system. The new tertiary process facilities include a covered Filter Building with four cloth disc filters, a Chlorine Contact Basin and Aeration Tank with positive displacement blowers, a Chemical Disinfection Building and an Effluent Pump Station to discharge treated wastewater into the Willow Slough bypass. The project also included a new lab building also upgrade and expand the existing Administration, and Maintenance Buildings.