SAN FRANCISCO — A gate that got stuck days ago, when workers repaired a pipeline hole spewing millions of gallons of Hetch Hetchy reservoir water into the air, is reducing the water supply to the San Francisco Bay area.
Bay Area water districts have been forced to supplement the shortage with water from their reserves, but customers had not been affected as of Wednesday.
To fix the 2-inch by 3-inch hole in the pipeline near Modesto on Sunday, workers had to shut down a 30-mile stretch of pipeline. To do that, they had to close a major gate in the system, and the gate got stuck when they tried to open it back up.
The gate controls water flow to the three major lines pumping water from the Hetch Hetchy reservoir in the Sierra Nevada to the Bay Area 160 miles away. The blockage has cut the water supply to the Bay Area’s 2.4 million customers by about half.
On average, the system delivers 210 million to 240 million gallons of water daily to the Bay Area. On Tuesday, demand for water was only around 197 million gallons, and the San Francisco Public Utilities Commission was able to deliver 198 million gallons from Hetch Hetchy and water treatment plants in Sunol and on the San Francisco Peninsula, said Patricia Martel, general manager of the SFPUC.
A dive team checked out the gate Wednesday to see what caused it to get stuck and was working to get it open, but there was no word on when the pipeline would be unblocked.
In the meantime, the SFPUC asked local water agencies to forego using Hetch Hetchy water during the peak hours of 5 a.m. to 9 a.m. and 6 p.m. to 8 p.m.
The Alameda County Water District, which gets about 30 percent of its water from Hetch Hetchy, was pumping more groundwater to make up the difference, said district General Manager Paul Piraino.
“We have not really seen any specific effects from the voluntary cutbacks,” he said.
The hole in the 1960s-era pipeline and the blockage came about a week after San Francisco voters approved a $1.6 billion bond to upgrade the water system, parts of which date to the late 1800s. Its pipes and tunnels cross three major earthquake faults — the San Andreas, Hayward and Calaveras faults — and scientists have said a strong quake could leave several cities without their main water source.