The atmospheric river that soaked Del Norte County last weekend also overwhelmed Crescent City’s sewage treatment plant, officials said Friday.

The treatment plant was pushing 8 to 10 million gallons of wastewater per day Saturday through Tuesday, said City Manager Eric Wier. On Monday, with the plant experiencing overflow conditions, the city released less than 5,000 gallons of partially treated sewage into the bay adjacent to the facility, he said.

“We contacted the environmental health department and were instructed to put up signs warning people,” Wier said Friday, referring to the Del Norte County Environmental Health Division. “We received clearance from environmental health yesterday to remove the signs.”

Large and small solids were removed or had settled from the effluent that the city released from the wastewater treatment plant on Monday, Wier said. City staff were working into the night through Tuesday to contain the overflows, he said.

“We can handle a large rain event,” Wier said. “A large rain event for multiple days is what really the treatment plant because the ground is so saturated at that point a lot of it ends up pushing its way into the pipes and then it overwhelms the treatment plant.”

The rain gauge at Jack McNamara Field received 7.51 inches of rain between Saturday and Tuesday, according to National Weather Service meteorologist Doug Boushey. The atmospheric river began Sunday, continued into Monday and moved south on Tuesday, he said.

Rainfall amounts reached 0.93 inches at the airport on Wednesday and Thursday, according to Boushey. Higher precipitation totals were reported inland with the Gasquet Ranger District receiving 9-10 inches during the atmospheric river last weekend, he said.

Last weekend’s heavy rains caused sewage overflows from 1,000 gallons to nearly 14,000 gallons in the cities of Eureka, Fortuna, Rio Dell, Ferndale and the Humboldt Community Services District, the Eureka Times-Standard reported Wednesday. Though it didn’t appear to affect the area’s drinking water, the Times-Standard reported that sewage likely made its way into waterways including the Humboldt Bay and the Eel River.

Heavy rain also overwhelmed the Grants Pass Wastewater Treatment Plant, forcing plant managers to dump untreated excess sewage into the Rogue River, KOBI-TV in Medford reported on Monday. In a 24-hour period, overflow at the wastewater treatment plant in Grants Pass was more than 20,000 cubic-feet-per-second. Maximum outflow of treated water at the Grants Pass plant is 3,000 cubic-feet-per-second, according to KOBI-TV.

Meanwhile, Boushey said another system will bring light rain to southern Humboldt, Trinity and Mendocino counties over the weekend, but Crescent City, Gasquet and other places in Del Norte County should be dry through Monday.

“Tuesday is probably going to be our next chance for rainfall,” he said, adding that meteorologists are giving a 40 percent chance of rain for Tuesday during the day and an 80 percent chance for Tuesday evening.

Wier congratulated the efforts his public works crew went through to not only address the overwhelmed conditions at Crescent City’s wastewater treatment plant, but weather-related issues in general earlier this week.

“We had some really tired individuals by the time the storm was over,” he said. “They were working around the clock for three days and three nights straight trying to prevent this. They really did an excellent job.”

Reach Jessica Cejnar at jcejnar@triplicate.com .

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