Monte Rio Beach will remain closed to swimming for at least one more day as public officials continue to pursue the reason for elevated lab tests that indicate contamination of the water with harmful bacteria, the Sonoma County Department of Health Services reported Monday.
The decision to keep beach-goers out of that stretch of the Russian River through at least Tuesday extends the ongoing beach closure to a fifth day, though officials have yet to confirm or pinpoint any specific hazard or source of pollution.
But state guidelines governing water quality required the closure last week because of test results above the state-allowed threshold for two indicator bacteria considered markers for possible fecal contamination. The beach status is now considered day-to-day.
The latest round of testing put total coliform bacteria at 11,199 organisms per 100 milliliters of sampled water collected off the beach Sunday, Deputy County Health Officer Karen Holbrook said. The state standard is 10,000 organisms per 100 ml.
E. coli was measured at 149 organisms per 100 milliliters in samples taken Sunday. The state standard is 235 per 100 ml.
E. coli levels dropped below the safety threshold July 6 and appear to have stayed there, though they remain above the two-digit numbers typical of routine testing at 10 Russian River beaches conducted by the county.
The highest test result in the past week put the E. coli level at 833 organisms per 100 ml. or almost four times the state standard, possibly as a result of huge crowds at the beach over the July Fourth weekend.
Human beings, even those with good hygiene, normally shed small amounts of fecal bacteria, which can cause test levels to spike when large numbers of people are present, said Alydda Manglesdorf, a senior environmental scientist with the North Coast Regional Water Quality Control Board.
She added that total coliform — the bacterial marker that has remained high — is not as good a metric for human fecal contamination as E. coli, which has declined in concentrations at Monte Rio.
Total coliform bacteria is common in the world at large, in soil or in vegetation, even, and doesn’t prove the fecal coliform is present.
“When the E. coli comes down and the total coliform remains up, that’s less” of a concern, Holbrook said. “It may be that it’s sediment that’s stirred up from the bottom that isn’t necessarily a fecal release.”
But because there are other possibilities, the county has been working with partner agencies and stakeholders to better understand what is going on, she said.
Two representatives from the county planning and environmental health departments were out on the river in kayaks on Monday, for instance, sampling the water up- and down-stream of Monte Rio Beach and looking for any obvious problems.
Inquiries and inspections have been made about septic tanks, porta-potty operations and homeless encampments as well, in an effort to narrow down the cause, she said.
“It could be that there is an ongoing release or leak that we haven’t identified, and that could come from a variety of sources: bodies out in the water with diaper accidents, or a porta-potty that’s been tipped over that’s still leaking, or a septic system, or animals that are near the water.”