Swimming and Water Testing

Why does the City of Purcell test for E. coli in Purcell Lake?
Purcell Lake is a great local source of recreation for our community.  We want to provide the necessary information for our swimmers to understand the risks associated with swimming in any natural body of water.  Signage is posted at the beach informing swimmers of our rules as well as information about the risks and ways to protect themselves.  Lake water is tested to determine if the amount of bacteria reaches a level that the Environmental Protection Agency advises we post an advisory.

When does the City of Purcell test for E. coli in Purcell Lake?
Testing will occur between Memorial Day and Labor Day of each year.

Notice Sign Will Be Placed In Swimming Beach Area if Test Results Exceed 320 CFU of E. coli.
The Environmental Protection Agency (EPA) research recommended a value of 410 colony forming units (CFU) of E. coli per 100 mL as the threshold for an advisory for recreation waters use. The City of Purcell has chosen to use the more conservative value of 320 CFU that was offered in the research for a lower threshold.

Other visitors are swimming even though a notice sign is posted. Is it safe?
The City of Purcell will post test records on this page and when above 320 E. coli CFU on the beach to inform the public.  This policy allows visitors to make their own decisions about recreation in the Lake.  As always, consider your level of health before a choice of activity in the Lake.

References and Guides

For more information or guides for safely enjoying any public waters, please visit any of the following links:
Swimming in Oklahoma’s Lakes, Rivers, and Streams, Oklahoma Department of Environmental Quality
Tips to Keep You Safe at Lakes, Rivers, and Streams, Oklahoma Department of Environmental Quality
Blue-Green Algae, Oklahoma Department of Environmental Quality
Recreational Water Quality Criteria, Environmental Protection Agency
Travel OK - Lake Conditions Website

The City of Purcell has referenced information from different sources to establish our testing policies. One example is the Chickasaw Recreational Area, who state on their website:
"Bacteria levels may fluctuate from day to day. When collected samples exceed E. coli limits, the public health standard requires the previous four weeks be averaged with the current readings to monitor long term trends. If the five week average and/or geometric mean is above the action level, the beach is posted with a sign notifying the public of high bacterial levels in the swimming area. When both the five-week average and geometric mean fall below the action level, the notices signs are removed.”