The City of The Dalles Wastewater Treatment Plant has discharged effluent that exceeds the plant’s limit for E. coli due to incomplete disinfection. Sample test results read on the morning of October 28, 2025, indicated an E. coli exceedance. Several resamples in the following 24-hour period confirmed that the treatment process is not under control. The cause of the exceedance is unknown at this time.

Operations at the City of The Dalles Wastewater Treatment Plant are improving, but are not yet back in compliance after a recent plant upset that resulted in discharge to the Columbia River of treated wastewater exceeding the plant’s limit for E. coli. Wastewater treatment staff are working hard to restore the biological balance so that the plant can quickly return to normal operations.