Project Overview

San Francisco’s 884,000 residents rely on the Southeast Treatment Plant (SEP) to process about 80 percent of the city’s combined sanitary sewage and stormwater runoff at a rate of 57 million gallons per day (MGD), with peak flows reaching 250 MGD during large storm events. Built in 1952, SEP was the oldest and largest of San Francisco’s three wastewater treatment plants, with many facilities operating beyond their useful lives.

Sundt and its JV partner replaced the two existing headworks facilities with a single, vertically integrated, all-weather 250 MGD facility featuring Hydro Headcell® technology. The project was constructed within a highly constrained urban site located in a mixed industrial, commercial and residential area, with homes across the street and existing roadways, railroad tracks and process facilities nearby. The team maintained continuous plant operations throughout construction, including critical tie-ins to an 84-inch influent pipe without unplanned interruptions to existing treatment processes.

The new facility improves screening and grit removal, protects downstream equipment, reduces odors and supports the city’s Level of Service goals. Its design accommodates dramatically varying flow conditions, handles grit loads nearly 10 times greater than typical industry levels, provides resilience against earthquakes up to magnitude 7.8 and accommodates 36 inches of anticipated sea-level rise by 2100.

The project also included community job training and outreach to small, local and historically disadvantaged businesses as part of San Francisco’s larger Sewer System Improvement Program.