MESA, AZ — Construction recently started on the expansion of the Signal Butte Water Treatment Plant on 84 acres north of Elliot Road and east of Signal Butte Road in Mesa, Arizona. McCarthy Building Companies Inc. is serving as the the general contractor and Black & Veatch is the engineer of record on the multi-phase plant expansion project.

Construction on the $56.6 million phase I facility expansion includes building an 8-million-gallon potable water reservoir as well as adding redundancies to ensure system reliability and provisions for the plant’s future expansion. The project team is also currently in preconstruction of phase II of the plant’s expansion. Phase I of the project is expected to complete in October of 2026, and phase II is expected to complete in early summer 2027.

Phase II of the expansion project will double the plant’s water treatment capacity from 24 million to 48 million gallons of water per day. The project includes adding a mirrored, sand-ballasted flocculation and ozone generation and sodium hypochlorite generation disinfection process, as well as solids handling. In addition to expanding the plant’s treatment capacity, phase II of the project will also enhance plant operations. During construction, all elements of the water treatment facility will remain operational.

“As southeast Mesa continues to develop, the Signal Butte Water Treatment Plant expansion reflects our city’s proactive approach to meet the needs of the community while planning for future growth. This project strengthens our infrastructure and reliability, ensuring we can provide clean, safe water as this area of Mesa continues to thrive," said Christopher Hassert, City of Mesa, Water Resources Director.

The original plant opened in 2018 and was master-planned to accommodate future expansions. This is the project’s first expansion, which is being driven by continued growth and development in southeast Mesa. The raw water that feeds into the Signal Butte Water Treatment Plant comes from the Central Arizona Project (Colorado River). The plant utilizes an ozone oxidation purification process to treat the water and meet rigorous drinking water standards.

“Our team of water experts is pleased to be working with the City of Mesa again, particularly as municipalities in Arizona and in states across the west work to address water issues,” said Tim Nicoll, Project Director with McCarthy Building Companies. “Delivering reliable water infrastructure for the growing East Valley is a shared goal of everyone on the team at Signal Butte, and this is driving innovation by the team to maximize cost savings while ensuring quality and certainty for the community. It’s exciting to be getting the construction portion of the project started.”

“By providing design and construction support to this critical project, Black & Veatch will leverage its more than a century of expertise in critical human infrastructure in helping the City of Mesa achieve its goal of enhanced reliability of its water supply,” said Mike Orth, President of Black & Veatch’s governments and environment market sector. “We welcome the opportunity to continue our long-standing relationships with Mesa and McCarthy Building Companies, delivering the innovation and solutions that help tackle pressing water issues.”