A malfunction in the final stage of treatment at a City of Portland wastewater plant led to an overnight discharge of mostly-treated wastewater to the Willamette River near Lake Oswego’s Foothills Park.
Out of an abundance of caution, the City of Portland Bureau of Environmental Services is advising the public to avoid the river around the park for 48 hours due the possibility of increased bacteria in the water.
The Tryon Creek Wastewater Treatment Plant at 195 Foothills Road in Lake Oswego serves a portion of SW Portland as well as Lake Oswego. The wastewater had undergone all stages of treatment except the final one - the addition of a disinfectant. A pump that delivers disinfectant failed around midnight and was repaired by about 5:30 a.m.
The overnight volume from the plant was one-third of the normal flow, and crews estimate about 500,000 gallons was released to the river without the disinfectant.
The City of Portland and Lake Oswego are working together on a plan to replace the aging Tryon Creek Wastewater Treatment Plant. More information can be found at Wastewater Treatment Facility.