Monte Rio Beach on the lower Russian River was declared safe for swimming and was reopened to the public Wednesday, just in time for a heat wave that’s expected to send temperatures back toward the century mark this weekend.
Sonoma County health officials still aren’t sure what was behind elevated bacteria levels that prompted the beach’s weeklong closure, though they suspect heavy crowds over Fourth of July and the preceding weekend likely had something to do with it.
Whatever the problem was, it has faded over the past week, according to the county, as near-daily water quality testing showed dropping levels of contaminants at the popular public beach, one of the last before the Russian River makes its tidal run to the coast at Jenner.
“We’re definitely going to continue monitoring, but it’s back down within acceptable limits,” said Deputy County Health Officer Karen Holbrook.
After really strong weekend visitorship all summer, the closure was a blow to the Russian River Recreation and Parks District, which runs Monte Rio Beach.
Despite posted signs warning people to avoid contact with the water, some visitors have continued to swim, as well as rent kayaks and canoes. The signs came down on Wednesday, said Steve Baxman, the parks district chairman.
“Hopefully people will realize it’s just a one-time deal,” he said Wednesday. “Hopefully, people come back.”
The latest test samples, collected at Monte Rio on Monday, showed a total coliform level of 7,772 organisms per 100 milliliters of water. The threshold at which fresh water is deemed potentially unsafe for swimming, wading and other recreation involving direct water contact is 10,000 organisms per 100 ml.
E. coli levels on Monday tested at 13 organisms per 100 ml., Holbrook said. The state standard for E. coli is 235 per 100 ml.
Total coliform and E. coli are both bacterial strains that are considered indicators of possible fecal contamination, though total coliform is a broad category representing a wide variety of potential sources, including soil and sediment.
Holbrook said it’s possible that heavy crowds stirred up enough sediment to contribute to the bacteria load.
It’s also possible that the sheer number of people, all of them naturally shedding bacteria, helped raise the levels, officials said.
In any case, surveys of the immediate area by land and by water failed to detect any other obvious source, Holbrook said.
The county health office routinely tests 10 Russian River beaches through the summer, and first saw signs of spiking total coliform levels at Monte Rio on July 3.
Retesting with samples collected July 5 showed rises both in total coliform and E. coli, which is considered a more likely marker of fecal contamination. Measurements at that time showed total coliform at 11,199 organisms per 100 ml, compared to an acceptable level of 10,000 organisms.
The E. coli level was 833 organisms per 100 ml., nearly four times the state threshold.
E. coli levels dropped quickly thereafter and have been at acceptable levels since the closure was in place.
The total coliform took a bit longer to resolve.
Holbrook noted, however, weekly testing of the 10 beaches this week turned up elevated levels of total coliform at Patterson Point, in the community of Villa Grande, about a mile downstream of Monte Rio.