Yes, it’s safe to swim in the Willamette most times of the year.
DEQ and the city of Portland regularly monitor bacteria levels in the river. Data collected since 2012 show that bacteria are almost always at healthy levels in Portland. It wasn’t always this way. In November 2011, Portland completed a 20-year combined sewer overflow (CSO) control program that greatly reduced untreated waste to the Willamette River. Before CSO control, combined sewers overflowed to the river an average of 50 times a year. Exposure to bacteria is the greatest health concern for people swimming or enjoying other sports on the river.
While generally it is considered safe to swim in the Willamette River, the river has a large watershed and pollutants can reach the water from many potential sources. Stay out of the water if it looks bright green, scummy or thick like blue green paint. This could be the sign of blue-green algae, which can produce toxins that are harmful to humans and pets. Also, bacteria can wash into the river following heavy rains, so avoid swimming at those times.
If you have any questions please contact DEQ Lower Willamette Basin Coordinator Andrea Matzke at 503-229-5350