Lake of the Ozarks testing finds one sample with elevated E. Coli levels

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Volume 37-328 For Immediate Release: Sept. 10, 2009

JEFFERSON CITY, MO. -- Water samples taken at the Lake of the Ozarks Tuesday found one sample out of 50 with E. coli levels in excess of the federal recommended maximum level for public swimming beaches, the Missouri Department of Natural Resources announced today.

Test results of water samples taken Sept. 8 found only one -- located in Laurie Hollow -- with E. coli levels above the U.S. Environmental Protection Agency's recommended maximum level for a single sample taken at a beach or designated swimming area of 235 E. coli colonies per 100 milliters of water.

That site, which is located on the west side of the lake's Osage River Arm north of Missouri Highway 5, posted E. coli levels of 378.4 E. coli colonies per 100 milliliters of water. Four other samples taken in the same cove had results of 5.2, 13.1, 13.4 and 40.4 E. coli colonies per 100 milliliters of water, which are below the federal recommended maximum.

Laurie Hollow was also the site of the only sample taken in July that exceeded the federal recommended maximum level. On Friday, staff from the Department's Southwest Regional Office will begin inspecting facilities in the cove's watershed that hold Department-issued wastewater treatment permits to determine if any of them might be contributing to the E. coli levels in that cove. The Department is also going to take additional samples in Laurie Hollow.

In the third year of a five-year testing program, the Department tested samples taken from 50 sites along the Niangua arm, and Linn Creek and Hurricane Deck areas of the Lake of the Ozarks for E. coli bacteria. The purpose of the program is to develop a five-year baseline that will assist in future studies of the lake's health. The 2009 final results will be available after the October round of sampling.

Testing during the 2008 recreational season found E. coli levels well within the standards for swimming at the lake. Based on the more than 320 samples taken last year, the lake had an overall geometric mean of 7 E. coli colonies per 100 milliliters of water. The state water quality standard for swimming and related whole body contact recreation is a geometric mean of 126 E. coli colonies per 100 milliliters of water during the entire recreational season. Because a geometric mean requires the collection of multiple data points over a period of time before a determination can be made, the Department compares monthly results to EPA's single-sample maximum recommended level of 235 E. coli colonies per 100 milliliters of water.

E. coli is a bacteria found in the intestinal tract of warm-blooded animals, including humans.  Some strains of E. coli can cause gastrointestinal illness.  These bacteria and other pathogens can reach lake water from many different sources, both human and animal.  For some people, such as children, elderly or those with weakened immune systems, even low levels of these bacteria may cause illness.

The sampling program is the result of a partnership of the Department of Natural Resources, 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. For more information regarding the Lake Ozark Watershed Alliance, please visit their web site at

A link to a map of the areas to be sampled is available on the Department's website at  Monitoring results will be posted to the map as they become available.