A joint venture between MWH Constructors and Webcor Builders this month was awarded a $939 million contract by the San Francisco Public Utilities Commission (SFPUC) to serve as construction manager/general contractor (CM/GC) for the Southeast Water Pollution Control Plant Biosolids Digester Facilities Project.

The Southeast Water Pollution Control Plant (SEP) was built in 1952 and is SFPUC’s largest wastewater treatment facility, treating 80 percent of San Francisco’s sewage and storm water flows. The Biosolids Digester Facilities Project (BDFP) aims to replace existing digester facilities with new, expanded, reliable, modernized and relocated facilities, as well as improve energy recovery and maximize control of odors.

Construction is expected to begin in summer 2018 with the facility becoming fully operational in summer 2025. The lead designer is Brown & Caldwell, with Black & Veatch and CH2M.

The four-acre project will be constructed in two parts to allow for continued use of the facilities. Part one includes the demolition and site preparation of the eastern portion of the SEP and existing asphalt plant, and construction of the new facilities on the site. Part two involves the demolition of the Central Shops and western portion of the SEP, with final completion of the new Biosolids Digester Facility following.

John Reynolds, Webcor Builders vice president, says design is currently about 65 percent complete. He says during the next year of preconstruction, the team will be doing cost estimates, developing the schedule, constructability reviews, preparing bid packages, and coordinating with the plant operators.

Reynolds says because of the project's location and complexity, the team is facing unique challenges

"It’s a major upgrade to an operating plant with very limited space, located in a neighborhood where we want to be careful to minimize impacts to the community," he says. "It has very complicated mechanical, electrical and control systems that need to be installed and connected in and around the operating plant that has to stay on-line 24/7. Managing any one of those elements by itself is fairly straightforward. When they’re all combined on one project, it presents more of a challenge."

Reynolds, whose company is also currently working on Phase Two of the Silver Lake Reservoir relocation for the Los Angeles Department of Water and Power, says they will overcome challenges on the Southeast Water Pollution Control Plant by working closely with the plant operations staff, communicating with surrounding neighbors and by planning, sequencing and executing the work in such a way to minimize impacts to all stakeholders.

"Total integration of the MWH/Webcor team with the SFPUC operational personnel will be vital to meeting this challenge," he says.

Project officials say the BDFP is one of the first projects in the U.S. to use the Cambi Thermal Hydrolysis Process (CambiTHP™). The CambiTH will enable the new facilities to produce higher quality biosolids, capture and treat odors more effectively, and maximize biogas utilization and energy recovery to produce heat, steam and energy.

Notable improvements in efficiency for the improved power plant will come through implementing the CambiTHP process, says Reynolds.

"The SFPUC chose CambiTHP because it reduces landfill waste by more than half, kills all the pathogens in the waste so it can be used as fertilizer instead of going to the landfill, and it produces significantly more methane gas that is used to produce more renewable energy," he says. "It’s really win-win, because the result is much less waste and a lot more energy."