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Dry weather sets off chlorine alarm at Tri-City wastewater plant

Staff at the Tri-City Water Pollution Control Plant in Oregon City responded to an alarm just after 4 a.m. Monday, Sept. 8, due to a small amount of chlorine being detected in an enclosed building.

“They weren’t physically there but their phones received the alert,” Gari Johnson, a spokesperson for Water Environment Services, which runs the Tri-City Service District. “Then they realized when they got there, it was a false alarm.”

Periodically, the waterwaster plant switches the source of its effluent. Due to unusually dry weather, there was not as much water to dilute the chlorine, causing some of the vapor to escape.

“It was the middle of the night. Nobody was using the bathroom, nobody was showering,” Johnson said. “As soon as everybody starting getting up and going to work, the water started going again.”

At no time was there a risk to the public. The plant has a sensor that activates an alarm to alert staff and neighbors of a potential issue. Chlorine is used at the plant to rid wastewater of pathogens and is removed prior to discharging clean water into the Willamette River.

Johnson said the wastewater staff aren’t likely to do another process change, which led to the vapors, again soon.

“We won’t be doing that again, not until it starts to rain again,” she said.

The Tri-City Service District, operated by Clackamas County Water Environment Services, provides wastewater treatment services to the cities of Gladstone, Oregon City and West Linn.

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