Workers Race to Repair Water Pipe : Studio City: Rupture threatens supplies for many in affluent hillside areas. Traffic to be impeded for at least a week.

City workers labored into the night to repair a 75-year-old ruptured underground pipe that threatened water supplies for hundreds of hillside residents, but city officials say it will be one week until normal traffic can be restored on busy Coldwater Canyon Avenue.

The five-foot-wide pipe burst Saturday morning beneath Coldwater Canyon Avenue in Studio City, uncorking a powerful geyser that flooded nearby residents’ yards, dug a 30-foot-wide crater in the road and forced a shutdown of the traffic corridor.

The spurting water also damaged an adjacent gas pipeline, prompting a brief evacuation of about 75 residents on Coldwater Canyon Avenue just south of Ventura Boulevard. By midday Sunday, most had returned to their homes, save for one family who lost about 10 feet of their front yard to the massive crater.

City officials said the pipe, laid in 1918, ruptured because rust ate through its steel walls. They said the problem was an unavoidable consequence of the aging of Los Angeles’ vast underground web of water lines.

“There is going to be excavation there until Friday at least,” said Ed Freudenburg, a Los Angeles Department of Water and Power spokesman.

An eight-inch temporary replacement line is expected to be installed today, but the crater created by the burst line will remain until mid-week, Freudenburg said. Then it would take two days more to fill in the hole and resurface the street.

Freudenburg said city transportation officials were still debating whether to close the road or create one-way rush-hour traffic lanes.

But Councilman Zev Yaroslavsky, who toured the site Sunday, said that even with designated detours onto side streets, using the road at rush hour “would be impossible.” He also noted that continuing roadwork on nearby Laurel Canyon Boulevard has already snarled traffic for hillside commuters.

DWP crews brought in dump trucks, a bulldozer and heavy crane to repair the broken pipe, which funnels water from the state aqueduct near Sylmar to a 2.2-million-gallon storage tank at the top of Coldwater Canyon.

That tank regulates water pressure and delivery to hundreds of homes in the upscale precincts between Coldwater and Laurel canyons and Mulholland Drive and Sunset Boulevard. DWP officials said that with replenishment water cut off, the tank had dropped to one-third of its capacity.

Water service to hillside customers was not interrupted, but officials worried that some could be without water or adequate water pressure as the tank level continued to drop.

“If that tank runs out of water, you’re going to have people without water and extremely low pressure, depending on where they are,” said Robert L. Simmons, assistant engineer in charge of DWP’s water operating division.

Officials urged residents to open their faucets as little as possible until the pipe is fixed.

Meanwhile Sunday, passersby gawked at the crater as residents pointed video cameras at hard-hatted DWP crewmen and tried to clean mud off their driveways.

John Moomjian, who lives across the street from the pipe break, sat on his front steps and recalled that the geyser Saturday “looked like Yellowstone National Park.” The break unleashed several hundred thousand gallons of water at rates of up to 10,000 gallons per minute.

Pat Chaimowitz, another resident, lost one end of her semicircular driveway to the crater, along with some rosebushes and other plants. She shook her head as DWP workers scurried through the neighborhood, testing water faucets.

“They keep turning it on and off,” she said. “I’m trying to do a wash here.”

Chaimowitz’s next-door neighbor, Fred Alaee, absorbed most of the damage from the crater, which sliced away a large portion of his front yard. Chaimowitz said Alaee had retreated to a home in Beverly Hills.

The city is engaged in a large-scale program to reinforce smaller water pipes with concrete, but officials said it was economically impractical to check for leaks on large-diameter pipes, such as the ruptured one, which would have to be dug up.

“There’s no real way at all of predicting where the problem spots are going to be” in larger pipes, many of which are decades old, the DWP’s Simmons said.

He said such problems are likely to increase in the future as the city’s vast spider web of water pipes continues to age and rupture.

Simmons said officials hoped to reopen the southbound lane of Coldwater Canyon to traffic by this morning, but a spokeswoman for the city Department of Transportation said that is unlikely. It will take two or three weeks before the street is fully repaired, Simmons said.

Times staff writer Chip Johnson contributed to this story.