Initially, the L.A. City Public Works claimed that the near catastrophic failure of the Hyperion Water Reclamation Plant in July, which not only flooded the plant but caused a 17-million-gallon sewage spill to be released in the ocean, was caused by a massive backup of debris.
At a February 11 L.A. Department of Public Works meeting, a report was presented and blamed human and technological mistakes. (To see the 53-page report, visit: Hyperion_Report
In July, Circling the News was skeptical of the debris claim because it was the dry season and a weekend day (Sunday).
CTN reported (“Hyperion Investigation Shows Breakdown Worse than Reported: Catastrophe Barely Avoided: Sewage Sent to the Ocean”) that “Trash started to overwhelm the intake screens that are used to rake and remove debris. As clearing the waste became more and more difficult, workers called plant executives to the site.
“By late afternoon the debris flow had wholly overwhelmed the building, requiring the evacuation of personnel due to what it called ‘life-threatening” circumstances.’”
CTN had contacted Elena Stern, L.A. Sanitation spokesperson in July, about the “debris” and she said, “The usual construction material, plastics, Styrofoam, but more than we’ve ever seen before.” She said the trash most likely came through the sewer system.
“There are 6,700 miles of sewer lines,” Stern said, noting that an investigation has started to look for the source of the debris. “We’re doing a survey and looking at all the lines.”
But the February report notes “there is little or no evidence in the conveyance system at this time to support an initial theory that a large influx of debris from outside the treatment plant suddenly overladed the plant’s Headworks.”
Instead, experts wrote that most likely equipment failed to transport the material out of the plant, and it instead recycled back into the Headworks, which caused an overload, with the four operating screens turning off.
The report notes that plant operators were not warned of the backup, which could be explained by a lack of technology (sensors, video cameras and an audible alarm). The report also cited insufficient staffing and emergency training for the staff.
People swimming in the ocean were not immediately warned of the sewage spill, although the Bureau of Sanitation notified L.A. County.
The report explains the delay may be associated with the analysis time for indicator organisms that the LA County public health department uses to determine beach closures.
“It typically takes one day to sample, analyze results, and report, while beachgoers may be exposed,” the report said. “On the other hand, there has been a past policy of L.A. County Department of Public Health to close beaches proactively after a spill of a significant magnitude and reopen after testing assures the beach is safe. That policy was not followed in this case.”
Many LA residents were sure the Headwater overflowed because trash had been dumped into manhole covers.
One consulting firm, Brown and Caldwell was hired to evaluate sewer lines. Using a “buoy” a Sewer Scout, they were able to access the sewer lines that are more than a mile long and cross under Los Angeles International Airport runways. They also used remotely guided robot to inspect the sewers closer to the plant.
They wrote “There is no evidence in the sewers to support the theory that a large influx of debris suddenly overloaded the bar screens.”
They did note that there was a buildup of debris, such as sand, but it had remained at the bottom of the channels and most likely did not contribute to the Headwater July failure.
A second group of consultants CDM-Smith evaluated the equipment, systems and practices inside the plant.
There are eight screens in the Headworks, and at the time of the failure, four were operating. At noon, the level of the water in the channels was 34.5 feet and peaked at 37.3 feet at 2:32, rising above the floor. Between 3:30 and 4 p.m., “sewage” water began flowing out of the building into the Hyperion plant’s internal streets.
An inaudible alarm was triggered at 2:11 in the plant’s central control room, but “was not acknowledged by plant operators.”
CDM-Smith recommended a closed-circuit video system so that the screens could be viewed at all times. Currently operators “have to walk up to covers and peer inside” and “it was difficult to see through transparent but cloudy covers.”
The consulting firm thought that the bar screen motors might be inadequate and noted that the distributed control system [DCS] had not been completed.
“Installing the DCS system for Hyperion was delayed because one of the contractors had a disagreement with the city over its implementation,” said Michael Stenstrom, a committee member and UCLA engineering professor who was quoted in a February 12 L.A. Daily News (“System, Humans Failed in Overflow”).
“The most high-tech DCS systems, Stenstrom said, are capable of remotely sending an alarm that calls a manager back into the plant.
“Had the DCS system been complete, the head operator at Hyperion, according to Stenstrom, might have detected the debris buildup and prevented the spill.”
The report recommends that visible and audible alarms be installed in both the Headworks and the main control room.
It was also noted that there were a large number of open staff positions at the plant and the report suggested staffing be reevaluated, adding “Headworks area is one of the least desirable places in the plant to work.”
Long-term plans for Hyperion, which is the largest water reclamation plant in the nation, is to become a full wastewater recycling facility by 2035. “It is essential for the Bureau of Sanitation to make immediate short-term improvements to avoid spills and other emergency events,” the report concluded.
“We also make a specific, long-term recommendation that BOS [Bureau of Sanitation] and BOE [Bureau of Engineering] analyze the conveyance system to predict the maximum short-term discharge that Hyperion can expect to receive in extreme events and compare this with the ability of Hyperion’s three areas of flood risk – Headworks, secondary influent pumping, and final effluent pumping – to handle it. This analysis is crucial to reducing future risks to the plant and should include consideration of the use of the diversions to convey flood waters out of the plant to avoid plant damage.”