Sunol Water Treatment Plant

Location: Sunol, CA

Owner: SF Public Utilities Commission

Contract: $50.8 Million

Role: General Contractor

Delivery Method: Design-Bid-Build

Result and Benefit to Client

The project was successfully delivered on time, within budget, and with zero claims.


Plant structures were strengthened to withstand seismic activity. Since the project was in an environmentally sensitive area with several migratory species, Monterey Mechanical engaged biologists and environmental engineers to implement environmental controls and to develop work plans to accommodate migratory species.

Project Description

Project enhanced process reliability and increased plant capacity from 120 MGD to 160 MGD peak capacity enabling plant operators to treat water separately from different sources.

Improvements included a new hydraulic flash mix, flow distribution structure, retrofit of existing flocculation basins with new vertical turbine mixers and the sedimentation basins with plate settlers, new sludge collection systems, replacement of filter valves and piping, filter-to-waste facilities, chemical feed facilities, a new water quality laboratory, modification of the plant control building and maintenance shops, and seismic strengthening of plant structures.

Challenges | Solutions

One of the biggest challenges to construction of the Sunol Valley Water Treatment Plant was access to the site, which was only available by a single-lane bridge with load restrictions. Monterey Mechanical recommended installing temporary falsework to strengthen the existing bridge, and we worked closely with SFPUC staff and the design engineer for successful design and construction. With traffic issues likely with a one-lane bridge, we implemented a traffic control plan to ensure smooth traffic flow during construction.

Smooth delivery of mega projects like the Sunol WTP do not happen without effective communications. To avoid miscommunications that can happen easily with multiple team members, firms, agencies, and subcontractors working together, a cooperative partnering relationship was implemented between all stakeholders early in the project.

Construction was in progress at the time of the 9/11 terrorist attack in New York City. With rising concern over the potential for water supplies being intentionally contaminated, it became critical to secure the site. Monterey Mechanical worked with law enforcement and SFPUC security staff to implement a badging system and checkpoint to control access to the site.

Awards and Commendations

American Public Works Association

Northern CA Chapter, Contractor of the Year Award, 2004