Sonoma County health officials have closed Monte Rio Beach on the Russian River to swimming, wading and other activities that would put visitors in direct contact with the water because of elevated bacteria levels in the wake of an extremely busy holiday weekend.
The Department of Health Services posted signs on the beach Thursday afternoon warning of contaminated water after recent testing that showed both E. coli and total coliform levels were above state standards, officials said.
Those bacterial strains are used as markers for the possible presence of fecal material, though the testing does not distinguish which E. coli strains may be present or whether any of the bacteria in evidence are from a human source or some other mammal, according to Dr. Karen Holbrook, the county’s deputy public health officer.
It’s also impossible to determine whether bacteria was introduced through some kind of septic tank leak, homeless encampment or some other form of direct contamination along the river.
The beach was crowded with people for four days, starting Saturday with the two-day Big Rocky Games, Sunday night’s fireworks, a busy Monday and overwhelming visitorship on Tuesday, Monte Rio Recreation and Park District officials said.
“Tuesday we had the biggest crowd we’ve ever had,” said Steve Baxman, district chairman and the local fire chief. “It was unreal.”
But the level of total coliform at Monte Rio already was elevated on Monday, when all 10 river beaches that are part of the county’s weekly testing program were sampled.
At that point, Monte Rio Beach’s result for total coliform was 10,462 organisms per 100 milliliter. The state standard is 10,000 organisms per 100 ml.
E. coli levels were well below the 235-organism-per-100-ml threshold, at 41.
Additional samples were collected at Monte Rio on Wednesday, under the county’s retesting protocol, and showed total coliform of 11,199 organisms per 100 ml.
Measurements of E. coli were 833 organism per 100 ml on Wednesday, almost four times the state standard of 235.
When those results came back from the lab Thursday showing excessive and increasing concentrations of both bacterial families, the need to close the beach was clear, Holbrook said.
None of the other Russian River beaches have shown exceeding levels of the contaminants.
Additional samples at Monte Rio were collected Thursday, with the possibility that lab results available today will show bacterial levels already have fallen below the state standard. If they do not, the health department will decide whether to test through the weekend, she said.
Baxman said he expected strong seasonal river flows to return the water to safe standards promptly, and said many beach visitors present when the signs went up on Thursday chose to stay, but just refrained from swimming.
Holbrook said river testing at all the beaches bounces up and down. She noted that Patterson Point, in Villa Grande on the lower river, had a total coliform level of 8,164 on July 3, 932 on June 26 and 1,658 June 19.
Cases of excessive bacterial levels have generally been relatively rare.
“I’m hopeful that this was a blip based on all of the bodies that were out in the water at Monte Rio Beach over the weekend and on the Fourth, and we timed our testing perfectly to capture that — that given a little time, that’s going to dissipate,” Holbrook said.