State Standard
The bacteria standard for Iowa’s recreational waters consists of two components.
- A geometric mean standard based on 5 samples in a 30-day period (126 colony forming units of E. coli bacteria per 100 mL of water).
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A one-time maximum standard based on a single sample (235 colony forming units of E. coli bacteria per 100 mL of water).
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Beach Classes
Beaches are placed on “vulnerable” list if they have violated the geomean standard two or more times in the previous five years. The list is reviewed annually to update the beaches classified as “vulnerable”.
Beaches are placed on the “transitional” list if improvements have been observed with respect to bacteria levels. Beaches in the transitional classification will be eligible to be reclassified to “non-vulnerable” if they do not exceed the geometric mean standard for one year.
Beaches that have not exceeded the geometric mean standard or only exceeded the standard once during the most recent five years are classified as being “less vulnerable” to experiencing prolonged or chronic problems with elevated levels of indicator bacteria.
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Posting of Signs/Advisories
All beaches are posted with signs that provide general information regarding ways to reduce the health risk associated with swimming at public beaches. These signs will also inform the public of current monitoring efforts and ways to obtain the data.
Advisories are generally updated on Thursdays between Memorial Day and Labor Day, but may be earlier or later in the week depending on the timing of holidays, sampling schedules and availability of laboratory results.
Beaches that exceed Iowa’s geometric mean water quality standard for bacteria (the geometric mean of 5 samples in a 30-day period exceeds 126 colony forming units of E. coli bacteria per 100 ml of water) will be posted with signs that state, “Swimming is Not Recommended”.
Posting will only occur between Memorial Day and Labor Day. The advisory remains in effect until the geomean drops below the water quality standard.
Vulnerable and Transitional Beaches that exceed the one-time sample maximum water quality standard for bacteria (235 CFU/100ml) will be posted with a sign that states, “Swimming is Not Recommended”.
Posting will only occur between Memorial and Labor Day. The advisory remains in effect until water quality samples taken from the beach drop below the one-time sample maximum.