Sewer line in Carson that failed, forcing beach closures in two counties, was near replacement

The failure of a 60-year-old sewage line in Carson that was due to be replaced in less than a year caused the massive sewage spill that forced health officials to ban swimming from Huntington Beach to the Palos Verdes Peninsula through the holiday weekend.

Crews for the Los Angeles County Sanitation Districts installed a total of eight bypass pipes by Saturday to finally stem the spill that began Thursday evening. The temporary lines carry waste around a 25-foot segment of sewer pipe that collapsed in the city of Carson, about a mile and a half south of the junction of the San Diego (Interstate 405) and Harbor (Interstate 110) freeways.

Officials at the sanitation agency said the 4-foot-wide concrete sewer pipe had deteriorated because of a buildup of sulfuric acid, a natural byproduct of organic material breaking down within the closed systems. The pipe also may have been stressed by last week’s substantial rainfall.

County sanitation officials continue to investigate the cause of the failure.

L.A. County sanitation officials estimated that between 6 million and 7 million gallons of sewage spilled from their lines and into the street in a residential neighborhood in Carson, where it then flowed into storm drains and into the Dominguez Channel, which carried it to the ocean. The spill was more than double the originally estimated size.

Health officials on Sunday continued to ban swimming from Sunset Beach in the city of Huntington Beach in Orange County north to Rancho Palos Verdes in Los Angeles County. The beaches will remain closed until daily testing for bacterial pollution shows contaminants have been reduced to an allowable level.

The health warning forced the cancellation of the 70th annual New Year’s Day Polar Bear swim at Cabrillo Beach in San Pedro. The swim had been canceled a year earlier because of COVID-19.

Los Angeles County Supervisor Janice Hahn on Friday called for an investigation into the cause of the spill, saying it was “dangerous and unacceptable.”

The sewer main failed Thursday afternoon near the intersection of 212th Street and Moneta Avenue, the waste backing up and flowing out of a manhole at 212th and Lynton Avenue, about three blocks to the west of the break.

By 9:27 Thursday night, emergency contractors had begun to install bypass pipes upstream from the blockage. Eventually eight lines and eight pumps directed the flow into the emergency above-ground lines, which carry the waste about 1,000 feet to another manhole, where the sewage is routed back into the main line.

Most of the flow from the broken sewer line was due to be redirected into a new sewer main near Figueroa Street, which is scheduled to come online in six to 12 months.

“We thought we had more time with this [old] one, but unfortunately that was not the case,” said Bryan Langpap, a spokesman for the country sanitation districts.

The agency will also attempt to install a smaller “slip line” inside the collapsed sewer pipe. That project should be completed within weeks, though sanitation officials did not provide a precise timeline. It will carry some sewage, when the bulk of the waste is directed to the new sewer pipe.

The county sanitation districts maintain 1,400 miles of sewer line, serving about 5.5 million people from Lancaster to the Harbor area.