The Abridged version:
- E. coli levels are down at all Lake Natoma testing sites where water samples are collected every Tuesday.
- E. coli levels have been safe for two consecutive weeks at Black Miners Bar Swim Area following five weeks of being deemed unsafe.
- The reason that the levels have dropped significantly after being elevated for weeks is unclear, according to California State Water Resources Control Board spokesperson.
Officials will lift swimming advisories at Lake Natoma following test results showing the presence of E. coli has dropped to safe levels for two consecutive weeks after being elevated for five weeks at Black Miners Bar Swim Area.
The lake was under a water quality advisory warning because of high E. coli levels from June 16 to July 14. The Central Valley Regional Water Board collects water samples at Lake Natoma on Tuesdays, and posts results online Wednesdays.
“The results are in and they are low across the board,” said Blair Robertson, California State Water Resources Control Board spokesperson.
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California State Parks will remove swim advisories when a site has two weeks of samples measuring E. coli levels below the safety threshold set by the Environmental Protection Agency in recreational waters.
Samples posted Wednesday show that levels at Black Miners Bar Swim Area, Nimbus Flat North Beach and the other three Lake Natomas testing sites were well below levels of concern for the past two weeks.
What’s the cause?
Water officials have said they don’t know why the E. coli levels were elevated, although a past study on the Lower American River found that birds can play a major factor.
“Bacteria are highly unpredictable — there are so many factors that may be influencing the fluctuation in levels, so we can’t say or speculate why that is,” Robertson said.
High levels of E. coli, a bacteria group found in the intestines of people and warm-blooded animals, may indicate fecal pollution in the water.
Although low levels of E. coli found in most bodies of water are considered safe, people exposed to elevated levels are at greater risk of becoming sick and experiencing stomach cramps, diarrhea, vomiting and fever.
