Casa Grande Wastewater Infrastructure Improvements and Water Reclamation Facility Upgrades

Wilson & Company worked with the City of Casa Grande, AZ, to develop a conceptual water design to support their growing community. The City needed infrastructure improvements to increase its wastewater collection and treatment capabilities to keep pace with the development of multiple large residential, commercial, and industrial complexes planned to come online within 2-3 years. The design included infrastructure improvements to forcemains, lift stations, gravity sewers, a reclaimed water distribution system (RWDS), and innovative upgrades to the water reclamation facility (WRF) to reduce costs while increasing capacity.

The City of Casa Grande needed to provide wastewater service to planned developments on the west side and relieve existing sewer interceptors on the east side, providing additional capacity to collect projected increases in wastewater demand since the current infrastructure is nearly at its design flow capacities. Two new lift stations and force mains will provide wastewater services for each region of the city to support proposed residential, commercial, and industrial developments. The 12 million gallons per day wastewater lift station facilities include three VFD-controlled submersible wastewater pumps in a wet well, an above-grade header, odor control, valves and appurtenances, new electrical service, instrumentation, and management within a site enclosure.

In the west, a new 24” reclaimed water distribution (RWDS) pipeline and dual 18” forces were consolidated into one trench along Kortsen Road, with installation going under a highway and railroad using Jack and Bore. A new 30,000 LF pressurized effluent line routed from the WRF to Bianco Road southwest of the WRF with a new Arizona Pollutant Elimination System (AZPDES) permit for the ability to discharge excess Class A+ effluent to the North Branch of the Santa Cruz Wash and Santa Cruz River. The force main features 12,000 LF of dual 18” HDPE pipeline routed from the new West Area Lift station to the existing facility.  In addition, a 5,000 LF of 36” HDPE sewer interceptor along Bianco Road will intersect with a 3,000 LF of 18” HDPE sewer lateral pipeline along Kortsen Road to combine within a 42” pipe to convey wastewater to the new lift station.

The capacity of the WRF, including the A+ effluent disposal, will increase from 12 mgd to 18 mgd. Wilson & Company relied on improving and retrofitting the existing unit processes without any significant basin or footprint expansions to accomplish this. The upgrades include the following modifications: Influent pump station capacity to 36 mgd, conversion of the existing abandoned pre-treatment basin to an equalization basin, replacement of the existing grit pumps, secondary treatment expansion from 12 mgd to 18 mgd by retrofitting the oxidation ditches with a suspended media fixed film system, expanding the current disk filters to increase redundant capacity, and upgrading the effluent pump station to accommodate a new RWDS.