Roughly two-thirds of the 70 million gallons of sewage spilled in Los Angeles County since 2007 ended up in a storm drain or a river connected to the Pacific Ocean, according to analysis of 15 years of data maintained by the county Public Health Department.
Of that total, the vast majority of the sewage that entered a waterway was inadvertently released in a single year: 2021.
A nearly catastrophic disaster at the Hyperion Water Reclamation Plant and the sudden collapse of a sewer system in Carson last year combined to make it the worst since the beginning of the data set in April 2007. The two spills, roughly six months and 15 miles apart, led to the total release of 25 million gallons of raw sewage either directly into the ocean or into waterways that empty into it.
In the 15-year period reviewed, there is no other year where more than 10 million gallons of untreated sewage made it to the sea, according to the data from the Public Health Department, which monitors ocean quality and tracks sewage spills reported by cities and other county agencies.
Spokespersons for L.A. city and county sanitation agencies — which combined own roughly half of the 17,000 miles of sewers in the county — say they are far below the state average for spills per 100 miles of sewers.
“I think it’s a case where both agencies were unlucky to have these unprecedented spills in one year,” said Bryan Langpap, a spokesman for Los Angeles County Sanitation Districts, the agency responsible for the sewer that collapsed in Carson. “In terms of the number of spills, we’re not seeing a spike.”
The data from public health suggests that L.A. County’s various public agencies have indeed steadily reduced the number of spills by as much as 70% since 2008. Yet, at the same time, the largest of spills by volume have nearly all occurred in recent years and fewer of those spills have been prevented from reaching the ocean. Approximately 92% of the 42 million gallons of sewage that reached a waterway connected to the Pacific in the 15-year period were spilled after 2015, the data shows.
Equipment failures blamed
The analysis of the data indicates that while grease and roots caused the most spills by far, the worst events were almost always caused by some type of preventable infrastructure failure. Though these failures caused only 4% of the 6,412 spills tracked in the database, roughly 63% of the total gallons spilled came from such events.
A comprehensive countywide assessment of Los Angeles County’s sewer infrastructure, approved by the Board of Supervisors in January, is underway in response to the Carson spill.
“The sewer pipe that collapsed in Carson and spilled 8 million gallons of sewage into our ocean in late December was nearly 60 years old,” Supervisor Janice Hahn said at the time. “We need to not only understand why that pipe wasn’t replaced sooner, but how our aging infrastructure in sewer systems across the county is holding up.”
These large scale spills are not inevitable in a major metropolitan area and could indicate a need for more funding for maintenance, said Luke Ginger, a water quality scientist for the environmental advocacy group Heal the Bay.
“It comes down to our infrastructure and how often we update and how well we maintain it,” Ginger said.
Hyperion spill the worst
The single worst spill in the entire 15-year period occurred in July, when a series of screens and chopper pumps designed to separate trash and large debris from incoming sewage failed at the Hyperion Water Reclamation Plant operated by the Los Angeles Sanitation and Environment, or LASAN. Water inside the plant rose rapidly, but the operators on duty did not notice the clog or the visible-but-inaudible alarm warning about the rising water levels until the flooding had reached dangerous levels.
At the same time, a high-tech computer system that could have remotely alerted the head operator of the flooding had not been fully installed, according to a report by an advisory committee formed by the Los Angeles Department of Public Works to investigate the spill.
The flooding led to the emergency release of 17 million gallons of raw sewage directly into the ocean to avoid the complete failure of the plant. The damage to the plant led to months of repair work and the additional releases of millions of gallons of partially treated wastewater from a pipeline 5 miles out from shore.
The problems
“It should have never happened,” said Michael Stenstrom, a UCLA civil and environmental engineering professor who co-authored the report. “In a better managed facility, it probably wouldn’t have happened.”
LASAN is currently evaluating and implementing the recommendations of the report, according to a spokesperson. The plant plans to install an audible alarm with a flashing beacon to alert to high water levels and will modify equipment to automate monitoring and improve resiliency.
Just six months after the Hyperion spill, a resident in Carson noticed sewage seeping up from a manhole at the intersection of 212th Street and South Lynton Avenue. County crews tracked the sewage back to a sinkhole and collapsed sewer on 216th Street. Approximately 8.5 million gallons of sewage is believed to have entered the Dominguez Channel as a result.
Reports in the months since have indicated this part of the sewer system was identified for replacement in 2015, yet only one phase of the three-phase replacement project was completed by the time of the collapse. Officials attributed the long delay to the complexities of designing and getting permits for a sewer replacement beneath a busy intersection.
“They were sort of gambling (about) the amount of time it was going to take to make the needed repairs, and they unfortunately ran of out time,” Hahn said in January. “We don’t want that to happen anywhere else in the county.”
The larger the sewer, the more complicated and expensive it can be to replace it, according to Stenstrom. In some cases, the entire street might need to be dug up, or a temporary sewer system constructed to divert the flows that would otherwise go through the damaged line.
“They’re difficult, expensive problems,” he said.
Pipeline inspections
Sewers in the city of L.A. and L.A. County typically are inspected on 15-year cycles and rated based on their quality. A sewer that is identified as potentially problematic will receive more regular inspections, officials said.
The 216th Street Relocation Trunk Sewer in Carson was last inspected by the county in November and early December and reportedly there were no indications of an emergency. Officials now suspect that a nearby manhole may have collapsed and caused the complete blockage of the sewer line. The manhole was looked at as part of the video inspection, but the low quality on the closed-circuit television systems used to inspect the sewer, which looks up at the manhole from the sewer, could have have missed the corrosion of the concrete, according to Sam Espinoza, the head of the Los Angeles County Sanitation District’s engineering department.
A series of large storms during that time period also might have contributed to the sudden collapse.
“This is not something we’ve seen before, but it’s really caused us to rethink the inspections of our manholes and maybe we need to do something different with our procedures in the future,” Espinoza said. The department is evaluating an upgrade to higher quality cameras for future inspections, according to a spokesperson.
A consultant is expected to provide a report detailing recommendations for improvements to L.A. County Sanitation’s programs and procedures in May.
Sewer inspections are typically done by running a camera attached to a wire through the pipeline. For the city of Los Angeles, it can take two to three months before a sewer pipe video is reviewed, according to a spokesperson.
Sewage drained into Ballona Creek
In 2018, a broken bypass pipe beneath Hyperion Avenue in Los Angeles led to a sewer draining directly into a storm drain for nine months. The line had been inspected by camera in February 2018 and then reviewed in April, according to Elena Stern, a spokesperson for LASAN. The inspector gave it a “B” rating on a scale of “A” to “E,” with “A” being the best quality and “E” indicating an emergency situation. Months later, in October 2018, an engineer was reviewing the same footage to look for maintenance access and spotted the issue.
Roughly 9.4 million gallons of sewage flowed into the drain connected to Ballona Creek over the course of the nine months the problem went unnoticed, according to a report by LASAN to the State Water Resources Control Board.
Some areas, however, are inaccessible by the most frequently used camera systems because of the length of the pipelines between access points. Stenstrom pointed to miles of sewer running beneath LAX’s runways as one example.
“There’s several miles of sewer that were not inspected for maybe 50 years,” he said. As part of the review for Hyperion, a new technology — a sort-of drone on a buoy — was used to inspect that portion of the sewer system to determine if it contributed in anyway to the Hyperion flooding. It didn’t, but these types of advances in inspection and maintenance — including potentially new pipe lining for existing sewers that can reduce corrosion — could limit spills in the future, Stenstrom said.
Most of the sewer systems use concrete, which can be corroded over decades by hydrogen sulfide produced by sewage, he said.
No ‘smoking gun’
Though Stenstrom is critical of the failures at Hyperion, he doesn’t believe the city or the county have a larger infrastructure problem.
“I don’t think there are real problems — like a smoking-gun kind of problem — with the maintenance in either the city of L.A. or the county,” Stenstrom said. “These two agencies do a relatively good job. I’ve seen much worse.”
Stenstrom, however, said one of his current concerns is whether the sewer systems in Los Angeles County, which were designed for high volumes of flowing water, are prepared for the low flows brought on by efforts to conserve water.
“When you have less flow, you can accumulate heavy materials,” he said. Then, it only takes one big storm to wash those materials into a treatment plant, or to create a clog, he said.
Those low flow cans also increase hydrogen sulfide.
In 2016, a sewer near 1600 E. Sixth Street in Los Angeles collapsed suddenly and spilled 2.4 million gallons of sewage into the L.A. River. Investigators believe the drought reduced sewer flows, which in turn increased the amount of hydrogen sulfide in the pipeline. It had been inspected in 2009 and given a “D” rating, the second worst of the scale of “A’ to “E.” Though the conditions were poor in 2009, it wasn’t scheduled for rehabilitation until the 2022-23 fiscal year, according to a report to the state.
Environmental impacts still unknown
The impacts to the environment from the massive spills in 2021 are still largely unknown, though preliminary results from trawling done late last year appeared to show no negative impacts to fish and other wildlife near Hyperion, the larger of the two spills, according to LASAN. The testing is not yet complete, however.
Back in October, LASAN officials stated it could take more than a year to study the impacts of the 17 million gallons of raw sewage released intentionally by Hyperion to avoid a larger disaster and the unaccounted millions of additional gallons of partially treated wastewater that were released for months while the plant underwent repairs.
Offshore sampling in the months after the Hyperion disaster showed spikes in e.coli and enterococcus as high as 6,000% and 3,200% above water quality standards, respectively, according to results at the time. But those samples were below a layer of the ocean called the thermocline, which acts as a barrier and, as such, prevents risk to beaches along the shoreline. Sewage at those levels can, however, still pose a risk to ocean life by blanketing the sea floor, clogging fish gills, creating dead zones and blocking sunlight.
It is difficult to say what the longer term impacts could be until more testing is done, said Ginger of Heal the Bay.
“There needs to be funding and there needs to be years of research” to determine the impacts, he said.
Though Ginger said LASAN’s description of its early test results seemed promising, he said he could not speak to the efficacy until the testing is complete and the data is released publicly by the city.