The City of The Dalles Wastewater Treatment Plant has discharged effluent into the Columbia River that exceeds the plant’s limit for E. coli due to incomplete disinfection, according to a May 30 press release from the City of The Dalles.

Sample test results May 28 indicated E. coli exceeded permit levels. Additional samples in the following 24 hour period confirmed that the treatment process is not under control.

The cause is an upset in biological processes at the treatment facility.

Rigorous water quality monitoring is ongoing.

The ultraviolet disinfection process has been ramped up to maximum capacity in an attempt to compensate for partially treated effluent release.

Wastewater treatment staff is working to restore the biological balance so that the plant can quickly return to normal operations.

Staff has increased frequency of sampling until E. coli counts are back within permit limits.

Signs have been placed at public river access locations on the Oregon shore of the Columbia River, from The Dalles Riverfront Park to West Mayer Park boat launch.

The signs reads: “Warning - Contaminated Water - No water contact,” and provide phone numbers to call for information.

For information about Washington shore public river access, contact Klickitat County Emergency Management at 509-773-4545.

The Department is in communication with the Oregon Department of Environmental Quality and local health department officials to coordinate response.

Questions can be directed to the Public Works Department office at 541-296-5401.

Updates an be found at

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