This week, DEQ began overseeing the cleanup of the last legacy contamination site in Portland’s downtown reach. From the mid-1800s to early 1900s, Portland Gas Manufacturing created the compressed gas that lit the street lamps. Today, the site is occupied by Naito Parkway and Tom McCall Waterfront Park between the Burnside and Steel Bridges.
NW Natural, which is responsible for the cleanup, entered the site into DEQ’s voluntary cleanup program in 2008. Since then, NW Natural has been working with DEQ to assess the extent of contamination, evaluate risk, create a cleanup plan and engineer how to remove the contaminated material. The cleanup will cost NW Natural $8 million.
“This really is an exciting moment,” said DEQ Project Manager Dan Hafley. “It’s the last significant cleanup on this part of the Willamette River and DEQ is using some new technology to ensure protection of humans and the environment during the cleanup.”
The project requires dredging contaminated sediment out of the river, hauling it away by barge and replacing it with clean fill combined with activated carbon to promote natural remediation of remaining contamination. During the dredging, NW Natural is using a system called a moon pool — a type of curtain that drops down to the bottom of the river around where the dredging will occur. As the contaminated sediment is dredged, the moon pool keeps the contaminated sediment from leaving the area. This is the first time such a device has been used on the Willamette River.
The work will take place between July and October. This time of year is called the “in-water work window.” It is the best time to do this kind of work because migrating fish, like salmon, won’t be in the area, and the river tends to be shallower and calmer since there is less rain.
– Lauren Wirtis, public affairs specialist