Nevada County officials on Wednesday identified the source of contamination in the South Yuba River that turned the water yellow and prompted a no-swim advisory for nearly a week.
Officials said in a news release that a property in the 13000 block of Kilham Mine Road in Nevada City was likely the source of the plume that moved downstream into Englebright Lake.
Nevada County spokeswoman Taylor Wolfe said an investigation is underway, so details are limited, but investigators identified “a sediment” entering the river from the property that “seems to be naturally occurring.”
The property was located by a California Highway Patrol flyover of the river, and officials with the California Department of Fish and Wildlife and the State Water Resources Control Board on Tuesday made contact with the property owner, who is cooperating with the investigation.
“We take this incident very seriously and we will continue to work with county authorities to determine what happened and what the impacts were to water quality in the area,” Andrew Altevogt, Central Valley Regional Water Quality Control Board assistant executive officer, said in a statement. “Once we’ve gathered the facts, we will determine the appropriate enforcement action to take.”
Investigators discovered multiple code violations on the property and county code enforcement is working with the property owner to rectify the violations.
The South Yuba River contamination was first reported Friday, when dangerous levels of E. coli bacteria were detected. The river was deemed safe Tuesday.
The Middle Fork of the Yuba River also briefly exhibited signs of contamination over the weekend, with a similar yellowing and high levels of E coli.
The presence of E. coli is often an indication of fecal contamination.
“After the preliminary tests showed dangerously high levels of E.coli at the Highway 49 Bridge of the South Yuba River, we were glad to have received recent results indicating no significant health concern,” Amy Irani, Nevada County Environmental Health director, said in a statement.
Investigators have taken soil and water samples from the property at the site of the contamination for testing, and Environmental Health officials will continue to test the river’s water to ensure safety.
County officials suggested that anyone who has symptoms of vomiting or diarrhea after making contact with the contaminated water since Friday should contact a doctor.