Los Angeles County’s Department of Public Works has made significant progress in reducing the odor coming from the Dominguez Channel that has plagued Carson residents and those in nearby cities for nearly a month, officials said Wednesday, Oct. 27, while confirming for the first time that their ongoing investigation is looking into whether chemicals from local refineries, chemical plants and other facilities are partially responsible for the stench.
Public Works Director Mark Pestrella and other officials provided those updates during the county’s second virtual town hall on what they have dubbed the Dominguez Channel Odor Incident.
“Our water sampling tells us our efforts are working,” Pestrella said. “So we’re ramping up and making good, good progress in seeing a downtrend in the hydrogen sulfide that’s creating this odor you’re all experiencing.”
The Public Works Department, which oversees around 483 miles of open channel and has taken responsibility for the odor, has continued to treat the channel water with a non-toxic and biodegradable odor neutralizer called Epoleon.
Crews had removed the 12 nano-bubblers used to pump oxygen back into the water ahead of the rain on Monday, but quickly reinstalled them on Tuesday. High-intensity lights are also planned to be installed to eliminate photosensitive bacteria believed to be contributing to the odor.
Pestrella has said the cause of the odor is decaying vegetation, which he has described as a naturally occurring phenomenon. But what’s different about this event, he said Wednesday, is that “we’ve had a more extended and persistent release of hydrogen sulfide than we have ever experienced.”
A survey of similar incidents nationwide showed such occurrences are not out of the ordinary, Pestrella said, but its duration is still troubling.
His department, Pestrella said, is also continuing to investigate incidents of illicit chemical dumping in the channel that could have acted as a catalyst in the process of the decaying vegetation, which is responsible for the gas release. The investigation, Pestrella said for the first time Wednesday, includes local refineries, chemical plants and facilities, and other sites adjacent to the channel, based on the theory that “something was shaken loose by the earthquake.”
He was referring to the magnitude 4.3 earthquake near Carson that shook much of the county last month.
“We’re attempting to rule out as many things as we can,” Pestrella said, “and will continue to do so until the end of this incident.”
Terrance Mann, deputy executive officer with South Coast Air Quality Management District, said his department continues to be fully deployed in the field and is using all the tools at its disposal. Those tools include mobile monitors, air sampling and the agency’s fixed air monitoring network, which is spread throughout LA County.
The agency also recently installed an additional monitor along Chico and 213th streets, making it the monitor closest to the channel.
“That water,” Mann said, “continues to show elevated levels of hydrogen sulfide in the middle of the night and the early hours of the morning.”
That coincides with when residents say the smell is most potent.
When the smell will completely subside, however, still depends on residents’ sensitivities to certain smells, officials say. Residents in Wilmington, Torrance, Long Beach, San Pedro and other neighboring cities have all reported smelling the odor.
County Health Officer Dr. Muntu Davis has said the reaction to hydrogen sulfide — which includes symptoms of headaches, dizziness, nausea and soreness in the throat, nose and eyes — differ among individuals. Residents closest to the channel, though, have reported experiencing ear infections, vomiting and hair loss.
Residents expressed various fears during the town hall Wednesday evening, including about what other chemicals in the channel could be affecting them. But Mann said that hydrogen sulfide is the only chemical currently being investigated as a problem.
“It’s not an issue that there is a laundry list of chemicals to present to the public,” Mann said. “Hydrogen sulfide is the only chemical that my agency and others participating in this investigation have identified as being directly caused by this event.”
AQMD, Mann said, had seen a steady decline in complaints this week, until noticing a spike Tuesday evening, Oct. 26, a day after rain showers had temporarily masked the stench.
As of Tuesday, Carson officials said, the city had relocated more than 1,300 residents to county hotel rooms, and continues distributing air purifiers at Victoria Community Regional Park, 419 M.L.K. Jr. St.
Residents affected by the odor should continue to call the county’s 211 hotline, officials said.