Southeast Treatment Plant Sewer System Updates

Cost: $9,536,000
Location: San Francisco, Calif. 
Year: 2019-12-01
Size: 250 MGD
Owner: San Francisco Public Utilities Commission  
Designers: San Francisco Public Works 
Contractor: Monterey Mechanical Co.

Located in Bayview Hunters Point, the Southeast Treatment Plant (SEP) is nestled in the midst of a mixed industrial, commercial and residential area; some neighbors are only a street’s width away from the treatment plant. The SEP is San Francisco’s largest wastewater facility, responsible for treating nearly 80% of the city’s flow.

Wastewater is transported to the SEP through a grid of transport/storage facilities, sewers and five major pump stations. On a dry day, SEP treats 57 million gal per day (mgd) and handles 160 wet tons of biosolids. During a rainstorm, it has the capacity to treat up to 250 mgd. 

Built in the early 1950s, many parts of the SEP facilities represent 1940s technology and are operating well beyond useful life. In fact, the existing digesters were placed into operation in 1951. In response to the need to modernize the aging wastewater infrastructure, San Francisco Public Utilities Commision (SFPUC) launched a $6.9 billion Sewer System Improvement Program (SSIP). 

SFPUC developed level of service goals for the projects to provide a compliant and reliable system to respond to catastrophic events; integrate green and grey infrastructure to manage storm water and minimize flooding; provide benefits to impacted communities; achieve economic and environmental sustainability; and maintain ratepayer affordability. 

To meet these goals, a new biosolids handling facility will be built to replace the existing system at the SEP. This will be accomplished in the new biosolids digester facilities project, however, these new facilities will not start commissioning until 2023. The existing digesters and associated facilities will continue to handle all biosolids generated by primary and secondary treatment operations at SEP until all planning for the new facilities are completed. The SEP existing digester gas handling improvements project bridged the gap in digester service for the next six years until the new digester facilities are put into operations.

Aging infrastructure and process equipment, avoiding disruption to plant operations, and avoiding air permit violations were pivotal to this project. The project absorbed significant additional work scope with the replacement of approximately
300 ft of waste gas piping and appurtenances due to leaks surfacing on piping above ground during the commencement of the construction phase.

As the upgrades continue at SEP, creative thinking, attention to detail, sensitivity to local residents and the ability to adapt to unforeseen circumstances will be critical.