Swimming beaches at Mark Twain, Wakonda state parks closed for weekend

The following is a press release from Wakonda State Park:

Elevated E. coli levels were found at two northeast Missouri state park swimming beaches this week.

Water samples drawn Monday from the public beaches at Mark Twain and Wakonda state parks showed E. coli levels in excess of the department's standard for state park beaches.

The water sample collected from the beach at Wakonda State Park had 307.6 E. coli colonies per 100 milliliters of water.

Samples from Mark Twain State Park Beach - which has yet to open this season due to high water - showed E. coli levels in excess of the department's standard.

When combined with samples taken the three previous weeks, the water at the park's public beach had a geometric mean of 138.2 E. coli colonies per 100 milliliters of water.

In order to provide a safer beach experience, the Department of Natural Resources will close beaches at state parks if the geometric mean for E. coli, which considers previous results in addition to the current week's results, exceeds 126 mpn/100 mL. The department will also close a state park beach if a single sample is above 235 mpn/100 mL for E. coli, which is also the U.S. Environmental Protection Agency's single-sample guideline for a swimming beach.

The two closed beaches have been posted with signs notifying visitors of the closure and will remain closed until E. coli levels fall below the department standard.

No other state park beaches tested high for E. coli levels; however, bacterial levels often rise after heavy rains and lake users should use their judgment when swimming after heavy rains.

The latest information on beach closings at state parks is available online at Additional beaches may be closed for other reasons, such as high water levels or safety and management issues. Information about all temporary closings at state parks is available online at

The 2,775-acre Mark Twain State Park is located in Monroe County in northeast Missouri along the 18,000-acre Mark Twain Lake. The 1,054-acre Wakonda State Park is located south of LaGrange in Lewis County.

The Missouri Department of Natural Resources, through its Division of State Park, manages 85 state parks and historic sites throughout the state, including 15 with swimming beaches. Water samples are taken weekly during the recreational swimming season to help ensure a safe public swimming area.

E. coli is a bacteria found in the intestinal tract of warm-blooded animals, including humans. While most strains of E. coli are harmless, some strains 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.