Workers have stemmed a 300-gallon-a-minute leak into San Francisco Bay from a sewage pipe at the Sausalito-Marin City Sanitary District in Fort Baker south of Sausalito.
District manager Bob Simmons said workers placed a collar around a curved section of the stainless steel 24-inch diameter pipe by mid-afternoon reducing the leak to about a gallon a minute.
Full repairs resume again Thursday and should be completed by Friday, Simmons said.
The section of the pipe containing the 2 1/2-inch hole will be plugged then encased in about 120 cubic feet of reinforced concrete, Simmons said. The Maggiore-Ghillotti Company of San Rafael will perform the work, Simmons said.
Simmons said a defective weld of a "hand hole" along the pipe is suspected of contributing to the leak that was reported around 1 p.m. Tuesday. Simmons estimated 500,000 gallons of partially treated sewage spilled into the Bay.
The sanitary district, which serves 18,000 customers, notified regulatory agencies of the spill and hired a contractor to repair the pipeline. However, the pipeline sits partially in the surf, and high tide prevented repairs, Simmons said. In addition, the rain has increased water flow from the Delta, making repairs especially difficult, he said.
The contractor attempted to perform a temporary repair using a wooden plug, but determined it could exacerbate the problem.
Simmons said signs have been posted at local beaches advising the public of the spill.
The sanitary district is working closely with Marin County health officials and water samples will be taken over the next few days, Simmons said.
"I don't think we've had any spills at the treatment plant of this magnitude," Simmons said of his district.