E. Coli Warning: Locals told to avoid contact with Columbia River water from The Dalles to Mayer Park

The Dalles, Ore., Aug. 2, 2025 — The City of The Dalles Wastewater Treatment Plant has discharged improperly treated effluent into the Columbia River, prompting warnings against water contact after E. coli levels exceeded permitted limits.

The discharge was first detected through a routine sample test read on the morning of Aug. 1, and subsequent testing over the next 24 hours confirmed that the plant’s ultraviolet disinfection system is not fully functioning. City staff say the cause of the malfunction is still under investigation.

In response, the disinfection system has been ramped up to full capacity and wastewater crews are working to restore the plant’s biological balance. Sampling frequency has been increased at the plant and in the Columbia River to monitor the potential spread and impact of the contamination.

Warning signs have been posted at public river access points on the Oregon side of the Columbia River, including The Dalles Riverfront Park and the West Mayer Park boat launch. The signs caution the public: “Warning – Contaminated Water – No water contact,” and provide contact numbers for further information.

“This is a serious matter, and we are taking every step possible to ensure public safety and environmental compliance,” said Amie Ell, public information officer for the City of The Dalles. The city is coordinating closely with the Oregon Department of Environmental Quality and local health officials.

People with questions about access on the Washington side of the river are urged to contact Klickitat County Emergency Management at (509) 773-4545.

The city has not announced when disinfection levels are expected to return to normal.