A valve on the water pipeline supplying Sonoma Valley ruptured late Wednesday morning, spilling about 16,500 gallons before workers could contain the leak.
A Sonoma County Water Agency crew was working on the pipe near the intersection of Melita Drive and Los Alamos Road in Santa Rosa at around 11:40 a.m. when the valve failed, tearing a 2-inch hole in the 24-inch pipeline, the agency said.
The leak was contained by 1 p.m., but repair work will continue until around 5:30 p.m.
The water was chlorinated, but crews were able to apply a dechlorinating chemical before the water reached nearby Santa Rosa Creek, the agency said, and there did not appear to be any damage to wildlife in the stream.
The crews were working on the 24-year-old pipeline as part of a long-term seismic upgrade on the regional water system, which supplies about 600,000 residents in Sonoma and Marin counties.
There were no injuries and drinking water service was not disrupted to any customers, the agency said.