More rotten smells expected from Vallejo wastewater treatment plant for another six months

VALLEJO — The foul smells that have been plaguing parts of Vallejo, originally estimated to be resolved by November, could persist for another six months or more.

The Vallejo Flood and Wastewater District received a spike in odor complaints last March after they began work to refurbish the south biofilter tower, a crucial piece of equipment at the city’s wastewater treatment plant. The district reported the work would be completed in November, but even though it was finished ahead of schedule, the odor complaints have continued.

Vallejo Flood and Wastewater District general manager Mark Tomko told the Vallejo Sun that  the district realized an odor scrubber failed while they were doing maintenance work on another piece of equipment. The odor scrubber filters air from the two biofilter towers and other equipment. It was found to be clogged and in need of a complete overhaul. Tomko said that work is now expected to be completed by the end of June.

Longtime Vallejo resident Terry Saltz told the Vallejo Sun that the bad smells from the plant began about three years ago, and the odor footprint has been spreading. He said the odor started seeping into the Georgia Street area about a year and a half ago, around the same time the cover was removed from the south biofilter tower. Saltz has been organizing neighbors to keep records of the time and place that odors are detected, weather conditions and wind direction, and sending a weekly log to the district. 

“These smells are just - it's unacceptable. Something has to be done,” Saltz said at the district’s board meeting last week. “I'm here to urge, if there's any interim measures or more aggressive odor abatement measures, that they need to take place, because it doesn't smell good for the city of Vallejo.”

District Operations Superintendent Orlando Cortez said during the meeting that the north biofilter tower cover was removed in October 2018 for maintenance, repairs and safety purposes, and that the south biofilter tower cover was removed in August 2023 in preparation for the scheduled project.

“The bio tower covers do not mitigate odors,” Cortez said. “The secondary odor scrubber, which draws foul air from the bottom of the bio towers, mitigates the odor.” 

Tomko said during the meeting that the secondary odor scrubber repair would take six months to a year, but that district engineers have since revised that estimate down to six months. To combat odors in the interim, the district will add misting fans at the perimeter of both bio towers, he said.

The smells on the ground at the plant are different from what the wind carries across Vallejo, so district staff rely on reports from the public. The nature of the smell can help them identify which component is causing the odor. A rotten egg smell indicates a problem with the headworks, where raw sewage first enters the plant, and a manure smell indicates a problem with secondary treatment systems.

Tomko said that, based on the majority of complaints, he believes repair of the secondary odor scrubber will solve the odor problem. “But my warning is that I don't know if that's the final solution,” he said. 

Wastewater board Vice President Mina Loera-Diaz asked the district to do some outreach and conduct a town hall meeting to better inform the public, and to update them periodically, “so we don't go another three, four, five, months with them just wondering,” she said. “There's a lot of people out there that have no idea what's happening, and they're putting up with this smell.” 

Loera-Diaz added that a lot of people in that area speak different languages, like Spanish and Tagalog. “We have to do it in a way that everybody's going to know what's happening,” she said.

Tomko agreed to work on broadening outreach and on finding a date for a community meeting after Christmas.

The public can help keep the district informed by notifying them of foul odors using this form.