The swim beaches at both Cherry Creek State Park and Chatfield State Park are back open after being closed Thursday due to unsafe E. coli levels.

Colorado Parks and Wildlife said tests Thursday morning that were part of routine water quality testing revealed higher than allowable levels of the bacteria, as determined by Colorado Department of Public Health and Environment (CDPHE) standards.

Chatfield swim beach reopened Friday afternoon and Cherry Creek reopened Saturday morning.

“While these closures are not common, we test the water often to make sure the public is safe while enjoying the reservoir,” Cherry Creek State Park Operations Manager Larry Butterfield said.

The beaches were to remain closed until water sample testing showed a decrease in E. coli, according to CPW.

“The elevated bacteria levels can be caused by fecal waste from wildlife, run-off from urban areas, or excessive run-off from rain, and the park has seen heavy rainfall this year.”

CPW notified the Colorado Department of Public Health and Environment (CDPHE) and the Arapahoe County Health Department and the Jefferson County Health Department of the testing results.

Regular water quality testing in natural swimming areas is required during the swimming season to ensure public health.