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 May 28, 2018 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 an upset in biological processes. 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 due to the upset. Wastewater treatment staff is working hard 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. Samples will also be taken at pre-arranged locations in the river to provide data on the effect of the discharge on water quality in the river.
Signs have been placed at locations of public river access on the Oregon shore of the Columbia River, from The Dalles Riverfront Park to West Mayer Park boat launch. The signs say: “Warning – Contaminated Water – No water contact” and give 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.
For updates go to the City website thedalles.org.