WALLA WALLA - Health officials are warning not to swim in Bennington Lake after moderately high E. coli samples were discovered there Thursday.
Officials with the Walla Walla District of U.S. Army Corps of Engineers put up signs around the lake on Thursday warning people not to swim in or drink from the lake.
According to Corps spokesman Bruce Henrickson, a stagnant aquatic environment created by low water flows may be the problem.
Henrickson also said it has been several yeas since the last time a high E. coli level had been detected at the lake.
The state threshold for E. coli in a body of water is 126 parts per 100 milliliters; Bennington Lake had a measurement of 175 parts per 100 milliliters.
Swimming in the water is the most likely risk at this point.
On Saturday, officials said they had to verbally warn several people not swim, and one completely disregarded the warning.
"We realize Bennington Lake is the largest recreational lake within a 15-mile radius. We do have people who swim in it, even though there is no designated swim area," Henrickson said.
The Corps take a monthly water test at Bennington Lake during the peak recreational season.
On Friday, Corps officials took several samples from around the lake; the results will be available Monday.
If the tests come back negative, the signs will be removed. If the high levels continue, Henrickson said the Corps will try to find a possible source to the contamination.
Boat launching and fishing are still permitted at the lake, but officials warn to use good hygiene, not to drink the water and to cook all fish thoroughly before consumption.