How does depaving help make the Willamette River swimmable?

July 5, 2016  |  Blog


Each July, hundreds of Portlanders jump into the Willamette River for The Big Float put on by Human Access Project. But is the Willamette River really safe to swim in?

Frequent water quality tests reveal that the answer is yes. Bacteria levels are consistently well below safety standards, so swimming in the Willamette will not make you sick. Get the latest test results.


Float On, the Willamette.

Things have changed

Several years ago, the Willamette River was not safe for swimming. Raw sewage flowed into the river during rainstorms about 50 times each year in “Combined Sewer Overflows” (CSOs). In older Portland neighborhoods, the rainfall that runs off rooftops, roads and driveways and into a storm grate is combined in the same pipes with sewage from toilets and sinks. The pipes used to be too small, so when it rained the mixture of sewage and stormwater would overflow into the river. Find out which neighborhoods have combined sewer pipes.

The Big Pipe

In 2011, Portland completed construction of “The Big Pipe” project. The largest of the big pipes is 22 feet in diameter and six miles long. That can hold a lot of water! Today, sewage overflows happen only in very intense rainstorms — about four times each winter, and roughly once every three years in the summer. The Big Pipe was the largest public works construction project in Portland’s history, and we are paying for it in our sewer/water bills. That is the price of making the Willamette safe to swim in.

Big Pipe

Portland’s Big(gest) Pipe

What about the Superfund site?

The Superfund site is in the most industrialized part of the Portland Harbor, from the Fremont Bridge to Sauvie Island, which is all downstream of the downtown waterfront. The contamination is in sediments on the river bottom and in resident fish. The most dangerous thing about the Superfund site is eating fish such as bass, catfish and carp that spend their whole lives in the harbor. Salmon are safer to eat, since they spend most of their lives in the ocean. EPA’s proposed cleanup plan is open for public comments until September 2016.

The pipe’s not getting any bigger

If we want to keep sewer overflows from happening more often, we have to keep stormwater out of the pipe system. That’s where depaving comes in. Replacing pavement with soil and plants helps rainwater percolate into the ground naturally, replenishing aquifers. And depaving keeps rainwater out of the piped system, reducing the risk of sewage overflows during rainstorms. The next time you’re tearing up asphalt at a depave, remember that you’re helping to make the Willamette River safer to swim in!

The Big Float happens this Sunday, July 10th. Get your pass and grab your water wings to join in.


Jump on in, the water’s fine — Join the Riverlution with The Big Float.

Leave a Reply

Comment moderation is enabled, no need to resubmit any comments posted.