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EPA, NW Natural will remove tar deposit from Willamette River Sediment this year

Release Date: 6/21/2005
Contact Information: Sean Sheldrake
(206) 553-1220

June 21, 2005

After carefully evaluating five alternatives for cleaning up contamination at the former GASCO site, the U.S. Environmental Protection Agency (EPA) has chosen a course of action that will allow timely removal of tar-laden sediment from the Willamette River, Portland OR while protecting human health and the environment, during the removal work.

The alternatives were presented for public review last month in an Engineering Evaluation and Cost Analysis (EE/CA). Under Alternative C, the selected action, about 15,000 cubic yards of contaminated sediment will be dredged from the site, followed by placement of a protective cap. The selected action includes an silt curtain system designed to contain contamination loosened during removal and prevent fish from entering the dredge area. The silt curtain will also be engineered to withstand boat wakes and high river flows. After considering public comments, EPA revised the monitoring approach described in the EE/CA to include additional monitoring for solid particles that might escape the silt curtain. Contamination will be taken by barge and then truck for disposal at the Chem Waste Subtitle C (hazardous waste) facility in Arlington, Oregon.

"The selected removal action eliminates a known source of contamination in the river and provides an opportunity to get an early start on cleanup," said Dan Opalski, EPA Regional Superfund Director. "EPA looks forward to working with NW Natural and other federal, state and tribal partners in the future to make sure there is a comprehensive and complete cleanup solution at the GASCO site."

NW Natural's cleanup of the tar deposit this year will be the first in-water cleanup action since the Portland Harbor Superfund site was listed.

The tar deposit at the former GASCO site was created by discharges from the oil gasification facility early in the 20th century, but the contamination remains in and on top of river sediment. The tar contains high levels of total polycyclic aromatic hydrocarbon (TPAH), as well as other chemicals, most notably benzene. The tar mass could also be eroded and redeposited if not removed.

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