Much has improved in the Tualatin River in the past few decades. Gone are the persistent algae blooms that came with inadequately treated sewage being dumped into the rivers and its tributaries. Now we have some of the best sewage treatment plants in the world on the Tualatin. But we still get questions about the safey of swimming and eating fish from the Tualatin
Pollution still enters the river from stormwater runoff. Runoff from only 26% of the urban landscape gets any kind of treatment. Areas where waterfowl are concentrated and fed may also prove a bacterial risk, so we urge everyone not to feed the ducks and geese at the park and to pick up after their dogs.
There are currently no health advisories against swimming in the Tualatin. The last one was in the summer of 2008 when we had a blue-green algae outbreak. The source of that outbreak was traced and fixed and we expect no more problems with blue-green algae.
In the winter and spring, the water is cold and there is current that is dangerous for swimming. There are no lifeguards on the river and lots of snags and downed trees. Wearing a personal floatation device (lifejacket) is a reasonable precaution. In the summer, the lower river has very little current and more people swim or wade in the river.
Mercury is detected in some amount in almost all rivers in the western United States. One source is from air pollution from coal-fired power plants in China that blows across the Pacific Ocean and is deposited with the rain. The U.S Geological Survey recently reported on mercury levels in fish from national parks in the west:
To be cautious, we recommend that you follow the fish consumption guidelines for the mainstem Willamette River.