Sewage Spill Shuts Parts of State Beach and Highway : Pollution: A major sewer line collapses near the Hyperion plant. Officials hope to reopen Dockweiler Beach today.

Authorities closed a two-mile stretch of Dockweiler State Beach and the westernmost end of Imperial Highway on Thursday after a major sewer line collapsed near the Hyperion sewage treatment plant in Playa del Rey.

Plant officials estimated that up to 10,000 gallons of raw sewage from the 48-inch-diameter line spilled onto the highway and entered a storm drain leading to nearby Santa Monica Bay. Plant manager John Crosse said crews would work through the night and try to have the pipe repaired by today.

A county health official described the spill as small and said the beach could be reopened by this afternoon if water samples show the seawater is safe. The spill occurred on the south side of Imperial Highway, just east of Vista Del Mar Boulevard.

“As spills go, this one is minor,” said Richard Kebabjian, a recreation official with the Los Angeles County Department of Health Services.

Crosse said the spill occurred near a construction area where workers are building two new lines to the Hyperion plant, which serves Los Angeles. One of the new lines is to replace the pipe that failed. As of late Thursday afternoon, the sewage flow had been contained, but not stopped.

Crosse said sewage from the broken pipe was flowing into a work site and into one of the two lines under construction. Had the sewage punctured a nearby embankment and descended unchecked to the plant, Crosse said, the situation would have been far more serious.

“It might have flooded the plant,” he said. “The flow from that line is about 40 million gallons a day, and it takes hours to stop.”

The beach was closed for a mile to the north and a mile to the south of Imperial Highway. The highway, meanwhile, was closed between Pershing Drive and Vista Del Mar Boulevard.

Seawater testing was being conducted by members of the Hyperion staff. John Dorsey, a biologist at the plant, said he would be surprised if significant pollution levels are detected when analysis of water samples are completed today.

“We’ve got a pretty good surf out there, so it’s going to be diluting pretty fast,” Dorsey said. “I’ll be surprised to see really high counts.”

Crosse said the cause of the pipeline collapse was not known, but he acknowledged that it may have been related to construction nearby on the replacement sewer lines.

He said plant officials have long considered the pipeline, which is made of cement, to be substandard and were hoping to have it replaced before a break occurred.

“I guess we were just a little too late,” Crosse said.