San Francisco’s public utilities agency has completed a $5.5 million emergency repair to prevent treated sewage from leaking into Islais Creek.
The project status was reported Wednesday to the Board of Supervisors Budget and Finance Committee, which approved the total project cost at $5.5 million.
When the leak was first discovered in October 2018, the project cost was initially estimated at $2 million, but subsequently increased due to factors including a change in project design and soil conditions.
At the time, the work was deemed an emergency in an Oct. 22, 2018 agency memo.
“This continuing leak of treated effluent into lslais Creek, rather than to the Bay through the deep-water outfall, could result in substantial regulatory enforcement action and penalties,” the memo said. “Immediate action also is required to mitigate potential public health risks.”
Tyler Gamble, an SFPUC spokesperson, said that The City “has provided timely and ongoing reporting on the status of the leak” to the San Francisco Bay Regional Water Quality Control Board. “The Regional Board has reviewed the reports and has not taken any action,” Gamble told the San Francisco Examiner Wednesday.
The pipe crosses Islais Creek to convey treated effluent from the Southeast Treatment Plant to the deep-water outfall in the Bay near Pier 80.
Gamble could not provide an estimate of how much treated effluent leaked into the creek but said that it was “only a small fraction of the volume of wastewater that is treated” at the facility in Bayview-Hunters Point. The facility treats two-thirds of The City’s sewage, about 50 million to 60 million gallons per day.
While the October 2018 memo mentions a public health risk, Gamble said that “there is minimal risk to public health because the wastewater is treated and disinfected, however, any damaged infrastructure presents some risk.”
“Southeast Water Pollution Control Plant processes, chlorinates, dechlorinates and routinely samples to ensure treated water is discharged to the Bay,” Gamble said. “Islais Creek is also being sampled weekly to ensure bacteria levels remain safe for water contact.”
The project costs increased for several reasons, including the need for a more extensive project design after a site inspection and after finding poor soil conditions.
“During construction to install the new bypass pipeline crossing Islais Creek, poor soil conditions at the site were revealed, necessitating the construction of watertight cofferdams (an enclosure system within a body of water to allow water to be pumped out, creating a dry work environment) rather than portable cofferdams, which had been included in the original construction budget,” according to the budget analyst report.
“The cofferdam construction required specialized crane and barge configuration and the construction of a temporary seawall,” the report continued.
The SFPUC is planning a larger project to replace all the wastewater pipes running across the creek.
“There is a longer term replacement project for the pipelines crossing Islais Creek,” Gamble said. “That project has recently reached 65 percent design completion.”