A Ruptured Pipeline Unleashes 10 Million Gallons of Raw Sewage : Thousand Oaks: Public health warnings are issued to avoid contact with water in creek and at four beaches near Point Mugu.

A broken Thousand Oaks sewer main has unleashed as much as 10 million gallons of raw sewage into Arroyo Conejo, prompting officials to issue public health warnings to avoid contact with the water at four beaches near Point Mugu and along the miles of creek that carry the sewage to the ocean.

City workers hope to staunch the flow of sewage early this morning from the 21-inch-wide pipe that they suspect ruptured sometime after Friday night’s torrential rains. Meanwhile, the sewage was pouring into the creek at about 3 million gallons a day.

“There is no way to physically just shut it off,” said Don Nelson, Thousand Oaks’ public works director. “We have to concentrate our efforts in affecting a repair.”

The county’s Environmental Health Department on Tuesday issued a public advisory to avoid any bodily contact with the polluted water.

“Our concern with the sewage is that it can create gastrointestinal problems: upset stomach, diarrhea and general unpleasantness,” said Robert Williamson, a manager in the Environmental Health Department. “There is also a concern about viruses, particularly hepatitis, which is a very serious illness.”

The spill from one of two feeder lines into the Hill Canyon Treatment Plant is the worst in Thousand Oaks since 1982. In January, storm runoff into the plant forced managers to release half a million gallons of partially treated sewage into the creek.

During the same January rainstorms, floodwaters in San Antonio Creek severed Ojai’s main sewer line, releasing 2 million gallons of untreated sewage down the creek that feeds into the Ventura River. Another major sewage spill came during the 1992 floods, when a broken pipeline spilled 6 million gallons of untreated effluent into the Arroyo Simi flood control channel in Moorpark.

Early Tuesday morning, Thousand Oaks officials discovered that about 50 feet of the pipeline had been washed away by swift floodwaters. They immediately posted signs in English and Spanish warning of sewage contamination along the Arroyo Conejo near to where it dumps into the Calleguas Creek near the Ventura Freeway.

County health officials said they have no plans to place signs along the remaining miles of Calleguas Creek that carry the water into Mugu Lagoon and then out to sea.

Instead, they issued a public announcement about the pollution and warned other area agencies, including the county agriculture commissioner, to make sure farmers are not drawing from the creek to irrigate crops.

The state Parks and Recreation Department immediately notified its rangers to instruct all swimmers, surfers and fishermen to stay out of the ocean at Thornhill Broome, Sycamore Cove and Leo Carrillo state beaches.

“People can still come down and walk on the beach, but we are advising them not to touch the water,” said Russ Guiney,superintendent of the Malibu sector that extends to Point Mugu State Park.

Immediately after receiving word, the Point Mugu Navy base posted signs closing its family beach to swimming, said Capt. Thomas M. Boothe, the base’s public works director. “It’s a small beach for Navy families,” he said.

Depending on how diluted the sewage is, Boothe said he does not believe the contamination will cause immediate harm to Mugu Lagoon, an ecologically fragile habitat for a variety of endangered birds and other rare species.

Nelson said public works officials have not been able to pinpoint when the sewer line was sheared, but believe the break occurred sometime after Friday night’s thunderstorms.

Over the weekend, the heavy rainwater flow compensated for what would have registered as a drop in sewage effluent arriving at the Hill Canyon plant, he said. And the break is located about half a mile from the nearby roadway and is not easily visible.

The discharge has created a foul odor along portions of the creek, but the Public Works Department had not received any complaints from nearby residents, Nelson said.

“This is not an area where people are going to be taking a stroll,” he said.

A dozen-member work crew labored into the night to repair the sewage line, which had lost four 12-foot sections to the racing floodwaters. Another three sections had been knocked askew.

First, crews had to bulldoze a short road to the inaccessible site. Then trucks dropped an estimated 100 tons of huge boulders into the creek to slow the erosion and support the rebuilt pipeline, said Mel Henson, a city public works superintendent.

Then, they started the tricky task of refitting the pipeline, while it continued to gush untreated waste water from nearly 25% of Thousand Oaks households.

“It’s like trying to fix a garden hose when it’s under pressure,” Henson said.

The department estimated it will cost the city $50,000 to $100,000 to make the repairs.

Jerrold Cherry, a nearby homeowner, said Tuesday night he was surprised by the spill so close to his house.

“I’m sure there’s going to be a lot of unhappy residents here,” said Cherry as he walked his two golden retrievers along the arroyo. “I’m disappointed that no one has been notified.”

Correspondent Ira E. Stoll contributed to this report.