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DEQ reports benzene spike after Mosier excavation; remediation and additional monitoring planned
Summary
The Oregon DEQ told the Mosier City Council that excavation removed 2,960 tons of contaminated soil and testing found benzene at 1,800 ppb in a monitoring well; contractors are doing bio-sparging and DEQ plans eight more monitoring wells and ongoing remediation.
Bob Shwarz of the Oregon Department of Environmental Quality told the Mosier City Council on July 20 that an excavation at the contaminated site removed 2,960 tons of soil and was completed on June 22.
"Benzene tested at 1800 ppb, which is 10 times higher than what is safe for a wetlands habitat," Shwarz said, and he described an intense initial on-site response that included flushing about 2 million gallons of water in the first 24 hours. CH2M and Clean Harbors are carrying out a bio-sparging operation and DEQ plans to drill eight additional monitoring wells to track concentrations over time.
DEQ’s presentation included maps and a site plan showing groundwater extraction wells and monitoring well locations. Shwarz said the immediate goal is to reduce benzene and other contaminants to nondetectable levels; he described ongoing fieldwork but did not give a precise timetable for when wells will show nondetect results.
Brett Vanderheuval of Columbia RiverKeepers asked whether DEQ would issue an administrative order to bind the railroad to a remediation timetable and cleanup standards. Shwarz described the technical work under way but did not announce an immediate order during the meeting.
Why this matters: the council heard that contamination levels detected at the site exceed concentrations DEQ described as safe for wetlands, raising concerns about local habitat and the need for ongoing monitoring and remediation. City officials, DEQ and contractors said they will continue sampling and remediation work.
Next steps: DEQ will continue bio-sparging and monitoring; the agency said it will drill eight new monitoring wells and track benzene levels until results meet cleanup goals. Columbia RiverKeepers said it will press for regulatory commitments from responsible parties.
