A pump station located in West Linn spilled about 300,000 gallons of sewage into the Willamette River after it lost power on Sunday.
'It's pretty big,' WES spokeswoman Amy Kyle said of the spill.
The station, operated by Clackamas County Water Environmental Services (WES) on behalf of the Tri-City Service District, is located near Willamette Park, between West Linn Paper Company and the former Blue Heron property.
Sewage poured into the river for an hour and a half as two of three pumps at the station were offline. The one remaining pump could not keep up with the flow, Kyle said.
The cause was an electrical problem that led to the pumps' failure. Power was restored and repairs were made within two hours by WES staff.
The Oregon Department of Environmental Quality, Oregon Emergency Response and Portland General Electric were notified of the incident.
As a precaution, signs have been placed near the site and the public should avoid contact with the river water nearby until the signs are removed.
'We ask people not to get in the water and to wash their hands if they have contact with the water,' said Kyle.
There is no backup system in case of electrical failure at the pump station, according to Kyle. WES is investigating what triggered the power problem.
The Tri-City Service District, overseen by Clackamas County, provides wastewater treatment services to the cities of Gladstone, Oregon City and West Linn.