Portland Harbor Superfund Site: River Mile 11 East Cleanup

GSI conducted a remedial investigation and feasibility study (RI/FS) and recontamination assessment of a contaminated stretch of the east side of the Willamette River in Portland, between the Broadway and Fremont Bridges.

GSI was selected to conduct a supplemental remedial investigation and feasibility study (RI/FS) in 2013 under an Administrative Settlement Agreement and Order on Consent (2013 AOC) between the U.S. Environmental Protection Agency (EPA) and six potentially responsible parties known as the RM11E Group. The project is located along the east bank of the Willamette River near the upriver end of the Portland Harbor Superfund Site. 

GSI helped the RM11E Group meet the obligations of the 2013 AOC by preparing all planning documents and implementing sediment, soil, groundwater, and porewater investigations to fill data gaps and facilitate the selection and design of a sediment remedy. All work products and the final report prepared by GSI were approved by EPA.

Following completion of the supplemental RI/FS, GSI conducted an assessment of the potential for recontamination of remediated river sediments from both upland and in-river sources. The Recontamination Assessment Report was approved by EPA in 2018—the first approved under the 2017 Portland Harbor Record of Decision (ROD). Meeting this milestone allowed the project to advance to the remedial design phase. 

GSI’s work on the recontamination assessment involved:

In 2006, GSI and our teaming partner began managing the technical elements of the project as a subcontractor to the Oregon Department of Environmental Quality (DEQ). Since then, we have implemented several complex research and monitoring projects including:

  • Developing a defensible process to narrow the list of chemicals of concern (COCs) to those with the potential to recontaminate the sediment remedy.
  • Performing a pathway-specific evaluation that included an evaluation of transport mechanisms and screening existing data to assess recontamination potential.
  • Considering and integrating upland source control work completed by individual parties under DEQ programs.

GSI is now supporting development of the Basis of Design Report and will continue to provide technical and facilitation support to the RM11E Group throughout the design.


Portland, Oregon


  • Facilitating negotiations and building consensus among multiple potentially responsible parties
  • Data management, interpretation, and visualization
  • Environmental sampling and analysis
  • Recontamination assessment

GSI’s contributions have been central to the development of a remediation plan for the upriver end of the Portland Harbor Superfund Site.

Photo Gallery

GSI staff member logging power-grab surface sediment sample

GSI staff members conducting groundwater monitoring at nearshore wells

Passive porewater and surface water sampler after removal

Collecting water depth measurement

Diver preparing to retrieve passive porewater sampler