The Columbia Slough runs parallel to the Columbia River and includes about 31 miles of waterway from the Willamette River to Fairview Lake. Industrial, agricultural and urban development along the Columbia Slough has resulted in contamination accumulating in the bottom of the slough. Some contaminants, including polychlorinated biphenyls (PCBs) and pesticides bioaccumulate in fish that live in the slough year-round. A fish consumption advisory was issued for resident fish in the Columbia Slough.
In 2005, DEQ issued a cleanup plan that established a program to clean up the slough. This program includes addressing individual sites that released contamination into the slough, controlling any ongoing sources of contamination, and monitoring conditions over the long term to make sure conditions were improving.
DEQ is working with many partners to address Columbia Slough contamination including:
- City of Portland to prevent elevated stormwater discharges associated with City Outfalls and city properties to the Columbia Slough.
- Private parties at many individual sites to prevent further pollution releases to the Columbia Slough and Columbia Slough sediment cleanup.
- Urban Flood Safety & Water Quality District's (formerly Multnomah County Drainage District) dredging operations achieve concurrent flood conveyance and remediation of sediment contamination where project objectives overlap.
- DEQ conducts investigations/sediment cleanups in various Slough segments using settlement funds obtained from private parties in exchange for a liability release for their site's contribution to contamination in Slough sediments.
Cleanup settlement
In 2024, DEQ and the City of Portland agreed to a $19.5 million settlement to address the city's contribution to stormwater and sediment contamination in the Columbia Slough. The City will pay DEQ a total of $19.5 million over three years to complete its cleanup work.
View the fact sheet to learn more about the settlement details including the work those funds will support.
DEQ held a public comment period on this settlement in November 2023, including a public hearing and several meetings with interested groups. An information meeting was held on Nov. 15, 2023.
More information
Industrial, commercial and agricultural facilities located within the Columbia Slough Watershed have contributed to sediment contamination through historical and current wastewater discharge, stormwater runoff, bank erosion and groundwater discharge. The following fact sheet provides additional information to understand Columbia Slough Sediment Liability for owners, operators and prospective purchasers within the Columbia Slough:
Below are resources for properties conducting an upland source control evaluation:
Columbia Slough Screening Level Values
The diagrams and additional information about the source control measures in the following areas of the Columbia Slough can be found in the 2024 Columbia Slough Annual Report.
Funds available for habitat enhancement
Habitat Enhancement Contributions