McCarthy Building Companies Inc. recently completed a $170 million Phase III expansion project at the Greenfield Water Reclamation Plant, located at 4400 S. Greenfield Road in Gilbert, Ariz. This project represents a 14 million gallon per day (MGD) expansion of liquids and solids treatment that allows the facility to treat up to 30 MGD of liquids and 38 MGD of solids on an annual average flow basis.
Three municipalities – the City of Mesa and Towns of Gilbert and Queen Creek – jointly own the treatment plant while the City of Mesa maintains and operates the plant. The original plant opened in 2007 and was constructed by McCarthy Building Companies in a joint venture with Sundt Construction.
Construction for the plant expansion started in November 2017 and reached substantial completion in August 2020, despite challenges this year with COVID-related restrictions on suppliers and subcontractors.
“This plant is the primary means of treating wastewater in the area,” said Pat Payne, project director for McCarthy, which served as Construction Manager at Risk. “As an end-of-the-line plant, it was imperative that plant operations be maintained. We very thoroughly vetted and planned all of our outages, and we didn’t have any unplanned outages.”
During the pre-construction phase, McCarthy and the design engineers identified more than 100 key outages, or maintenance of plant operations (MOPOs). As part of that process, McCarthy led weekly MOPO meetings with as many as 25 key stakeholders contributing ideas.
“The plant’s staff worked closely with the contractor to make sure they knew the constraints of the operation,” said Joseph Schroeder, P.E., Project Manager for the City of Mesa. “The plant was able to make changes to accommodate the contractor, and the contractor was able to make changes to accommodate the plant.”
Throughout the plant expansion construction, all elements of the plant remained operational and capable of producing A+ reclaimed water for the municipalities it serves. The liquids treatment processes include preliminary treatment via screening and grit removal, primary sedimentation, biological nutrient removal, secondary clarification, tertiary disk filtration, chlorine contact disinfection, chemical feed systems and effluent pumping. Solids handling and treatment include sludge screening, blending, thickening, anaerobic digestion, dewatering and gas handling. Other site improvements include comprehensive odor, noise and visibility control measures to ensure acceptance within the community. The plant is designed to meet Arizona Department of Environmental Quality Class A+ reclaimed water quality standards and Class B solids for land application or disposal. While expanding the treatment capacities, this project also enhanced operations of the plant, including replacement, repair and rehabilitation of aging equipment.
Carollo Engineers and Brown and Caldwell served as the design engineers and major subcontractors included Pipe Line Services dba Aims, Phoenix; Prime Controls, Tempe, Ariz.; Progressive Roofing, Phoenix; Harris Rebar, Phoenix; K&F Electric, Inc., Phoenix; Matrix Service, Tulsa, Okla.; Schuff Steel Company, Phoenix; and Sun Valley Masonry Inc., Phoenix.