What levels of indicator bacteria are considered safe?
The United States Environmental Protection Agency (EPA) has guidelines for the amount of bacteria acceptable in water bodies designated for primary body contact recreation, including swimming and water skiing. In Iowa, these waters are called Class A waters. The bacteria level in the water is acceptable if the geometric mean is not greater than 126 colonies per 100 milliliters of water for E. coli bacteria. According to U.S. EPA guidelines, the geometric mean is calculated using at least five consecutive samples collected during a 30-day period. Additionally, Iowa also has a “one-time” standart for E. coli bacteria of 235 colony forming units per 100 milliliters of water.
