While thousands of people fell sick during the recent Dominguez Channel hydrogen sulfide incident, water quality readings from authorities suggest that the channel was also uninhabitable for fish and wildlife during the peak of the incident, Los Angeles County officials said.

Since Oct. 3, residents of Carson and surrounding LA county communities, including Long Beach, endured elevated levels of hydrogen sulfide, a foul-smelling gas, for nearly two months. Residents’ symptoms ranged from pounding headaches to nose bleeds, even vomiting.

To address the air quality incident, the Los Angeles County Public Works formed a technical committee that includes the U.S. Environmental Protection Agency, the California Department of Fish and Wildlife and the Los Angeles Regional Water Quality Control Board to develop and implement “science-based solutions” to stop the odors emanating from the channel, Rossana D’Antonio, deputy director for development services and Emergency Management for the LA County Department of Public Works, said in an email.

At the peak of the incident in mid-October, D’Antonio said that dissolved oxygen concentrations within the channel were measured at 0 milligrams per liter, which is “insufficient for supporting aquatic life.”

According to the United States Geological Survey, dissolved oxygen is essential for the survival of fish and other aquatic organisms. Aquatic life may also struggle in stagnant water that has a lot of rotting, organic material, much like conditions at the Dominguez Channel during the incident.

The Dominguez Channel near the 405 Freeway exit on South Avalon Boulevard and East Dominguez Street on Thursday, Oct. 14, 2021. Photo by Crystal Niebla.

It’s unclear to what extent the odor incident affected wildlife in the channel. David Lin, a senior environmental scientist with the California Department of Fish and Wildlife, said he did not receive any reports of impact on fish and wildlife during the Dominguez Channel incident.

Following the treatment of the water in the channel by Public Works, which included using aeration machines, water quality data now indicates that dissolved oxygen concentrations are above 5 milligrams per liter, “which is consistent with a healthy aquatic habitat,” D’Antonio said.

Measures implemented by Public Works have improved water quality in the channel and air quality in the surrounding communities.

While Public Works does not monitor biological activity within the channel, county staff said duck activity was spotted on Nov. 23, and fish activity on Nov. 27, which D’Antonio said is “a welcome sign of the return of a healthy estuary.”

The Dominguez Channel, a 15.7-mile storm drain, is an estuarine channel that drains into the Los Angeles Harbor in the east basin. More than 70 species of fish and 400 species of invertebrates (e.g., shrimp and spider crab) have been documented in the harbor, according to an environmental report prepared for the California Regional Water Quality Control Board and the U.S. Environmental Protection Agency. More than 100 species of birds have been documented at the ports of LA and Long Beach, connected to the harbor.

Anyone who observes any fish and wildlife impacts can make a report to the incident to Fish and Wildlife by calling 1-888-334-CalTIP (2258) or visiting https://wildlife.ca.gov/Enforcement/CalTIP.

How did the Dominguez Channel stench start? An interactive timeline