EARTHQUAKE: DISASTER BEFORE DAWN : City Power Suffers A Pre-Dawn Punch : Utilities: Water, electricity and gas services are hit hard by temblor. Aftershocks could cause new problems.

The lifelines of water, electricity and natural gas that keep the sprawling Los Angeles metropolis working suffered some serious fractures Monday, most spectacularly shown in a fire at a cracked underground gas line in the northern San Fernando Valley and breaks in the two main aqueducts carrying water from Northern California.

Hundreds of thousands of area households were still without gas, power or water by Monday evening and authorities said it could take several days for full service to be restored. Residents of the Valley and neighborhoods north of Sunset Boulevard and west of Western Avenue were being warned to boil water before drinking in case of contamination through pipe cracks.

Officials were unable to estimate the damage in dollars to crucial infrastructure, but they expressed relief that the vast networks of pipes and transmission stations were not devastated even more.

For the Los Angeles Department of Water and Power, the most worrisome damage was at an electrical converter station on Sepulveda Boulevard in Sylmar that receives power from hydroelectric plants in the Pacific Northwest and distributes it into local grids.

“That’s a major, major loss,” said DWP spokeswoman Dorothy Jensen.

Also, several transmission towers bringing power into the San Fernando Valley from a generating facility at Castaic Lake were damaged, she added.

Because of the interdependence of Western power grids, brief power outages caused by the quake were reported as far north as Portland and Seattle.

Much of the Los Angeles area lost electricity in the quake, and about 520,000 of the DWP’s 1.4 million customers had not had their power restored by nightfall, officials said. In areas outside of the city of Los Angeles, Southern California Edison had restored power to all but 150,000 homes and businesses by late afternoon--and hoped to whittle that number down to 50,000 by nightfall.

The DWP had no count of how many households and businesses had lost water service, but the agency warned that wide swaths of the western San Fernando Valley might have low pressure or no water at all for days.

The water service problems are mainly caused by electrical outages that cripple pumping stations, said DWP official Jan Merlo. “At this point, it’s very difficult to say what the power situation is, so we are asking people to conserve water,” she said.

The older of the two aqueducts bringing water from the Owens Valley broke in an area south of Soledad Canyon near Santa Clarita. Water flow was shifted to the second aqueduct, which was later shut down after a crack was discovered in a section north of Sylmar.

Repairs on both concrete tubes--90 inches and 72 inches in diameter--were said to be under way. Authorities were not calling it an emergency because water supplies were said to be plentiful in a dozen area reservoirs.

There were no reports of major damage at area reservoirs or dams. But a major trunk line out of the Los Angeles reservoir complex in the Sylmar area sprung a five-foot-long leak and a filtration plant in that area was damaged, causing service problems in Simi Valley, Ventura County and the city of Los Angeles, according to the Southern California Metropolitan Water District, the regional water wholesaler.

The main gas problems involved breaks in four high-pressure transmission pipelines in the San Fernando Valley, including one that erupted into flames on Balboa Boulevard in Northridge, destroying two nearby structures. Those four breaks were later controlled through shut-off valves and transmissions were rerouted, said Rich Nemec, a spokesman for the Southern California Gas Co.

An estimated 150 gas distribution lines and individual service lines ruptured, contributing to fires in some cases. All those breaks were reportedly under control by noon. By Monday night, Nemec said, about 18,000 of the 4.7 million customers of Southern California Gas remained without service, a situation that may continue for several days.

“We feel pretty good in the way our own facilities have held up,” he said.

However, Thomas O’Rourke, a Cornell University expert on the effects of quakes on pipelines, said many more gas and water lines may have fractured than originally known, with further fires possible over the next few days. He said that the rupture of a water line under Balboa Boulevard may have caused underground erosion, undermining the nearby 22-inch gas line that burst into flames Monday.