No cause found for river pollution
The book is still out on the mysterious bacteria problem that discouraged bathers last summer from entering the South Yuba River.
Now its authors are hoping there’s no sequel. South Yuba River Citizens League just completed a 63-page report about Enterococcus, a fecal indicator bacteria that prompted no-swim advisories late last summer for much of the popular river
Tests showed Enterococcus levels 40 times higher than state guidelines to trigger beach closures. The South Yuba’s Enterococcus levels were comparable to in the Los Angeles River, which flows through the state’s largest city
Yet no one got to the bottom of the Enterococcus problem. Officials couldn’t figure out the bacteria’s source, and some questioned the reliability of the main test used to detect it.
If Enterococcus rears its head again this summer, SYRCL’s report proposes $35,000 worth of tests and studies to figure out what’s happening. If necessary, SYRCL will seek funding from the Nevada County Board of Supervisors, said SYRCL Executive Director Janet Cohen
“The Yuba is a large and important piece of the tourist trade here, and if it’s closed for another year, people will notice it economically,” Cohen said.
SYRCL’s report calls for double-checking of Enterolert, the principal water quality test used last summer to detect Enterococcus, by comparing it with other tests. Enterolert is made by Idexx Laboratories, Inc., a Maine-based company
Limited studies suggested that algae could interfere with the Enterolert test,” SYRCL’s report said
The Enterolert test requires putting water samples under ultraviolet light, which makes bacteria glow so they can be counted. The algae may have given off a false positive fluorescent signal, said SYRCL’s report
Yet, Enterococcus definitely was in the river, the report said
That was shown by another test which identified different species of Enterococcus, including those associated with human and animal feces
But the report goes on to question if it would have been likely – or even possible – for humans or animals to raise Enterococcus levels to those recorded in August at places like popular Purdon and Hoyt’s crossings
There would have to be … approximately 90,000 gallons per day of raw sewage entering the South Yuba River to achieve the observed Enterolert levels,” the report said
“To get a general idea of the number of animals required … over 8,000 ducks would be required to be living on the river daily … results from this calculation strongly suggest waterfowl were not responsible.”
Another puzzler: while Enterolert levels skyrocketed last summer, tests for another fecal indicator bacteria, E. coli, stayed low.
The report speculates that, unlike E. coli, Enterococcus may be able to survive or even grow in algae and sediment.
High flows this wet winter should flush out the river and may help the problem, Cohen said. SYRCL1s report is at Madelyn Helling Library in Nevada City and at the Grass Valley Library. It should soon be on SYRCL1s Web site at http://www.syrcl.org
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