In order to protect public health and safety, the City of Prior Lake monitors both of our public beaches (Sand Point Beach and Watzl’s Beach at Lakefront Park) for E. coli levels in accordance with Minnesota Rule 7050.0222. The City’s beach testing policy includes:
- Weekly water samples collected at both sites
- A beach will be closed if E. coli levels exceed 126 MPN/100 ml as a geometric mean of the last 5 samples
- A beach will be closed if E. coli levels exceed 235 MPN/100 ml for a single sample
- A beach may only be reopened when E. coli levels fall below 100 MPN/100 ml as a result of further testing
Watzl’s Beach water samples averaged about 16 MPN/100 ml for the 2015 swimming season before July 28, well below the threshold for beach closing. Watzl’s Beach was immediately closed on July 29 when the City received test results from two July 28 samples averaging over 900 MPN/100 ml. The City retested the water at Watzl’s Beach on July 30 and received the results on July 31. The test results indicate a low level of E. coli in the water (3 MPN/100 ml), and according to our policy, Watzl’s Beach will be reopened today. Sand Point Beach test results have not indicated elevated E. coli levels in 2015. Sand Point Beach continues to be open to the public.
It is not known what caused the temporarily elevated E. coli levels at Watzl’s Beach. Testing for specific disease-producing or pathogenic organisms is difficult, expensive, and time-consuming. Therefore, E. coli is used as an “indicator organism”, providing an indication of the possible presence of other pathogens. E. coli in lakes originates from animal waste (including humans, pets, livestock, and wildlife). E. coli bacteria themselves are not usually harmful but can be associated with other disease-causing bacteria or parasites. Swimmer’s itch is not caused by E. coli but is often found in areas with elevated E. coli levels.
Beach patrons can reduce their impact on beach water quality by leaving their pets at home and by not feeding the ducks and geese that frequent the beach areas.
The City will continue to test public beaches in accordance with our policy. Please contact Pete Young, Water Resources Engineer, at 952-447-9831 for more information about the testing program or lake water quality. For more information about E. coli and general beach safety, please visit:
Minnesota Department of Health: http://www.health.state.mn.us/divs/eh/beaches/howsafe.html
Minnesota Pollution Control Agency: http://www.pca.state.mn.us/index.php/view-document.html?gid=8543