San Francisco utility officials are probing a breach in a metal pipe in San Mateo on Saturday that sent thousands of gallons of treated drinking water into a creek and killed more than 100 fish.
A section of the 60-inch pipe broke open, sending drinking water treated with chloramine plunging into the San Mateo Creek, said Deborah Chilvers, spokeswoman for the San Francisco Public Utilities Commission.
Chloramine is a disinfectant used to treat water for human consumption but is toxic to fish, Chilvers said.
The thousands of gallons of treated water killed more than 100 fish, including steelhead trout, in the creek next to Crystal Springs Road in San Mateo near the Crystal Springs Reservoir, Chilvers said.
"We're still investigating the cause of it at this time," Chilvers said.
Utility employees have since repaired the pipe and halted the leakage, she said.
Corrosion within the metal pipe, which is about 80 years old, may have caused the breach and shifting ground beneath it also could have played a role, Chilvers said.
The damaged pipe had been slated for replacement by the PUC before the breakage, Chilvers said.
The pipe is part of a system that carries water from the Hetch Hetchy Reservoir in Yosemite, about 180 miles east of San Francisco, to the Bay Area where it is treated with chloramine, Chilvers said.
The water is used by the utility's ratepayers in San Francisco as well as in San Mateo, Alameda and Santa Clara counties.
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