Mo. Rev. Stat. § 640.080: E. coli measuring standard — posting of signs when beaches exceed, language — authority to close beaches.

1. For Missouri state parks' designated swim beaches, a standard that measures E. coli using the Environmental Protection Agency's Method 1603, or any other equivalent method that measures culturable E. coli, with the geometric mean (GM) of weekly sampling of one hundred ninety colony forming units per one hundred milliliters shall be utilized.

2. If beaches exceed the GM standard established in subsection 1 of this section, the department of natural resources shall post the beach with signs that state "Swimming is Not Recommended".

3. The department reserves the right to close a beach in the event of a documented health risk including things such as but not limited to wastewater bypass, extremely high sampling values, spills of hazardous chemicals, or localized outbreaks of an infectious disease.