Work crews finished patching a severed Thousand Oaks sewer pipe on Wednesday, but county officials remain concerned about the lingering public health threat from 10 million gallons of raw sewage that flowed down 18 miles of the Arroyo Conejo into Mugu Lagoon and out to sea.
In an advisory released Wednesday, Ventura County's Environmental Health Division urged the public to avoid contact with the running creek and ocean water within 10 miles of the lagoon for at least three days.
"On a scale of 1 to 10, our concerns are about a 6," said Robert Williamson, a county environmental health manager. "Contracting hepatitis is a fairly remote possibility, yet the infection in some cases can be very serious."
County public health officials said they have received no reports of illnesses related to the spill.
"If nobody swims in that area, we should not expect any," said Public Health Nurse Marilyn Billimek, who coordinates the county's infectious-diseases program. If people have contact with the water, she said, "we could get reports of skin infections. In about a month, we could expect some hepatitis."
The contamination does not threaten Thousand Oaks' drinking water, city officials said.
The 10-million-gallon spill is among the largest ever in Ventura County, Williamson said. But he added that it does not compare to spills five or 10 times that size that occur in heavily populated areas of Los Angeles and San Diego counties.
Environmental officials believe the spill will not harm the federally protected harbor seals, the American peregrine falcon or other endangered species that feed and nest in Mugu Lagoon.
"I don't see a problem to the marine mammals or the birds in Mugu Lagoon," said Ron Dow, head of Point Mugu Navy base's environmental division.
Most of the viruses carried by sewage tend to pose health threats specifically to humans, he said, and they can collect in harmful levels in clams and mussels.
"There might be a period where we wouldn't want people collecting clams for human consumption," he said. "We've got our signs up on our beaches."
Cat Brown, a wildlife biologist with the U.S. Fish & Wildlife Service, said raw sewage can kill some sensitive native species. But this spill, she said, occurred at a fortunate time--during the winter, when many species are less active and less vulnerable.
She said it also helps that the creeks are still flowing, diluting the waste water and washing it into the ocean. Should the sewage water be trapped in the lagoon or portions of the creek, its bacterial breakdown could deplete oxygen in the water and kill fish.
"These spills go on constantly," Brown said. "It is a little bite here and there against a healthy environment. How many bites does it take before the system doesn't function anymore? We don't know."
Thousand Oaks Public Works Director Donald Nelson said the city has tested creek water near the ruptured pipeline and found high levels of fecal coliform. The city will continue bacterial tests in the Arroyo Conejo and keep its signs in place warning of the sewage contamination at least until Monday.
County environmental health officials will not post signs along Calleguas Creek, nor on those beaches where they recommend avoiding bodily contact with water.
"We don't have enough people who can go out along miles of creek and post signs every 50 yards," Williamson said. "And then people will say, 'Why didn't you put one here?' "
Williamson said that a portion of Thornhill Broome State Beach has been roped off. And state park rangers are patrolling beaches down the coast to warn swimmers, divers, surfers and fishermen to avoid contact with the polluted waters.
The sewage spill began late Friday night or early Saturday morning after the racing waters in the swollen Arroyo Conejo ripped apart six 12-foot lengths of the line that carries waste water from central Thousand Oaks.
With extra storm water entering the Hill Canyon Treatment Plant downstream, city workers did not notice a drop in sewage flowing into the plant. They finally discovered the pipe break about 7:30 a.m. Tuesday morning, during a routine post-storm inspection of the lines.
"Even if we had known about it Saturday morning, we might not have been able to fix it any sooner," Nelson said. Floodwaters had swollen the Arroyo Conejo about 10 to 15 feet and crews would not have been able to reach the break.
The pipe continued to release sewage at 2 1/2 to 3 million gallons a day for the next four days, he said.
Laboring under spotlights, work crews managed to plug the leak about 9 p.m. Tuesday. By 1 a.m. Wednesday, they finished refitting the eroded section of pipeline and restored the sewage flow to the treatment plant.
Workers returned Wednesday to fortify the patched pipeline so it would not be undercut again by the corrosive forces in the creek.
Using a large loader and other earth-moving equipment, a crew from a Camarillo pipeline contractor placed a protective layer of boulders around the exposed pipeline and encased it with three truckloads of concrete.
"This is a permanent fix," said Frank Cote, president of JFJ Construction Inc., who supervised the emergency repair job. "This will keep the creek where it belongs."
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
Sewage Spill A ruptured pipeline unleashed 10 million gallons of raw sewage into a Thousand Oaks creek. The sewage flowed 18 miles downstream into Mugu Lagoon and then out to sea. County health officials warn the public not to touch contaminated creek water for 72 hours. *
Spill Site: Workers on Tuesday discovered a 50- foot section of pipeline washed away by raging creek waters. *
Mugu Lagoon: An ecologically fragile habitat for federally protected harbor seals. It also provides food and shelter to a variety of endangered birds and other species. *
Beaches: Health officials advise staying out of the surf within 10 miles of the lagoon.