Retesting of Lake of the Ozarks Cove finds decrease in E. Coli Levels

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Volume 37-332 For Immediate Release: Sept. 12, 2009

JEFFERSON CITY, MO. -- Follow-up water sampling conducted Friday at a Lake of the Ozarks cove found four samples taken directly from the lake with E. coli levels below the federal recommended maximum level for public swimming beaches. Higher than expected bacterial levels from a nearby wastewater treatment facility are prompting a second inspection of the facility, the Missouri Department of Natural Resources announced today.

Testing of four samples taken Friday from Laurie Hollow Cove found E. coli levels well within the U.S. Environmental Protection Agency's recommended maximum level for a single sample taken at a beach or designated swimming area.

Department staff returned to Laurie Hollow Cove after testing results from samples taken Tuesday showed E. coli levels in one of the five samples taken to be roughly one and one-half times the EPA recommended maximum. The highest E. coli reading of the four samples taken directly from the lake Friday was approximately one-twelfth the EPA recommended maximum. Two of the four samples were taken at the site of the elevated results from earlier this week.

Staff from the Department's Southwest Regional Office on Friday also inspected the only facility in the cove's watershed that holds a Department-issued wastewater treatment permit. Because of higher than expected bacterial levels in a water sample taken at the facility, inspectors will return Monday for additional testing and inspection.

Immediately retesting coves with samples in excess of the EPA recommended maximum is a proactive step the Department instituted this month. Follow-up inspections of permitted facilities within a cove's watershed have been a standard practice since the start of the sampling program.

Laurie Hollow Cove, which is located on the west side of the lake's Osage River Arm north of Missouri Highway 5, was also the site of the only sample taken in July that exceeded the federal recommended level. In both July and September only one of the five samples taken in the cove was above the federal recommended level. In both months, the other samples were well below that level. Residents of the cove have reported to the Department that a flock of ducks has taken up residence in the cove.  Waste from waterfowl is one possible source of E. coli.

E.coli bacteria can accumulate and dissipate quickly depending on circumstances and can concentrate in relatively small areas. This explains why a location with high readings on Tuesday can be considered within tolerable limits on Friday, and how four locations within a single cove can be within limits, while the fifth is considered high.

In the third year of a five-year program, the Department is testing samples taken from 109 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.

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 126 E. coli colonies per 100 milliliters of water during the entire recreational season. A geometric mean is a statistical method used to analyze data collected over a period of time.

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.

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.

For more information regarding the Lake Ozark Watershed Alliance, please visit their website at