Lake of the Ozarks October sampling finds no elevated E. coli levels

Seasonal Totals Well Within State Standard

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Volume 37-374 For Immediate Release): Oct. 9, 2009

JEFFERSON CITY, MO. -- This season's final set of water samples from the Lake of the Ozarks found none with E. coli levels in excess of the federal recommended maximum for swimming areas, and the overall testing results for the summer found E. coli levels for the lake at less than one-tenth the state standard for swimming, the Missouri Department of Natural Resources announced today.

With October's sampling, which closes out the recreational season, the department has collected and analyzed 332 water samples from the Niangua arm, and Linn Creek and Hurricane Deck areas of the Lake of the Ozarks. The geometric mean for the entire recreational season -- May through October -- was 8.8 E. coli colonies per 100 milliliters of water.

The state water quality standard for lakes and rivers that support swimming and related whole-body contact recreation is a geometric mean of 126 E. coli colonies per 100 milliliters of water. A geometric mean is a statistical method used to analyze data collected over a period of time.

Testing during the 2008 recreational season found the lake with an overall geometric mean of 7 E. coli colonies per 100 milliliters of water. In 2007, the first year of the five-year testing program, the season's total was 4.9.

In October, a total of 59 samples were tested for E. coli bacteria. The highest of those samples was approximately one-tenth of the U.S. Environmental Protection Agency's recommended maximum level for public swimming areas.

EPA has established a single-sample recommended maximum level of 235 E. coli colonies per 100 milliliters of water for public swimming areas. The highest E. coli level found in the October sampling was 24.6 colonies per 100 milliliters.

E. coli is a bacteria found in the intestinal tract of warm-blooded animals, including humans. Most strains of E. coli are harmless, but some can cause gastrointestinal illness. Because the purpose of the testing is to provide baseline information for future comparison, rather than providing immediate public health data, the testing method used by the department does not differentiate between strains of the bacteria.

The department tests for E. coli because it is considered a reliable indicator of the possible presence of other more harmful bacteria. E. coli and other pathogens can reach lake water from many different sources, both human and animal.

The sampling program is a partnership of the DNR, the Department of Conservation, Ameren UE and the Lake of the Ozarks Watershed Alliance, which provides trained volunteers to collect the samples. Ameren also pays $15,000 per year for the five-year study. When completed, the water testing will include coves from Bagnell Dam to Truman Dam.

A link to the results and a map of the areas sampled is available on the department's website at Monitoring results will be posted to the map soon. For more information regarding the Lake Ozark Watershed Alliance, visit their website at