Near the seawall (eastern upland boundry), groundwater impacts have been observed in upland wells, notably in the 65-75' bgs, with MGP constituents including benzene and naphthalene observed. Groundwater above and below has minimal or no contamination. In the river, significant sediment contamination has been detected off of Block 4 and 5, and to a lesser extent Block 21. Contaminants detected included VOCs, PAHs, metals, and cyanide (all MGP waste constituents). Block 5 was the locus of MGP operations at the former PGM facility.

Summary of Investigative Work:

In October 2012, additional source control work was completed at DEQ's request. Work included sediment sampling to define the lateral extent of sediment impacts, pore and river water sampling, seismic profiling of the riverbed, and a diver survey of riverbed debris and a tar area. Upland work included a transducer study using site wells. Results were presented in a site investigation report presented to DEQ.

A Draft Integrated Sediment Investigation/Source Control Evaluation Report, including a comprehensive risk screening for both upland and in-water contamination, was completed by Anchor for NW Natural in April 2013. Based on comments by DEQ, a Revised Integrated Sediment Investigation/Source Control Evalution Report was submitted in Aug. 2013. Risk screening identified elevated concentrations of MGP contaminants in both upland groundwater (largely in the 65-75' bgs zone), and Willamette River sediment adjacent to the site.

To finalize the RI and risk screening work and prepare for a site feasibility study, a Supplement to the Integrated Sediment Investigation/Source Control Evaluation (Nov. 2013) was submitted by NW Natural. A revised Supplement was approved by DEQ in Feb. 2014.

Two FS-related documents, a FS Work Plan and Annotated FS Outline were submitted by NW Natural in early 2014. The work plan outlined additional in-water investigation work including porewater and seepage rate measurements, and advancing cores to better delineate sediment impacts in the northeast portion of in-water contamination. This work was approved in June 2014 and implemented that summer.

An Integrated Feasibility Study report was submitted for DEQ review in December 2015. DEQ issued comments on the FS dated February 11, 2016. Under the draft FS, the proposed remedy consisted of a combination of active (dredging, capping) and passive (natural attenuation) elements. The FS was finalized (Aug. 2016) and subsequently approved by DEQ. A DEQ Staff Report outlining the proposed site remedy was prepared (Oct. 2016) and approved by DEQ management.

Record of Decision issued by DEQ July 3, 2017. Included response to EPA, tribal, and public comments and evaluation of remedy consistency with that for Portland Harbor. A Pre-Design Work Plan was completed by NWN in August 2017 and approved by DEQ. Work including an updated bathymetric survey, diver survey, and sediment collection and was completed in September/October 2017.

Remedial Design and Remedial Action:

A final (100%) remedial design document was submitted to DEQ in May 2019, and comments prepared by DEQ. Final revision of the document is expected in June, after which it will be approved. Plans call for development of the separate long-term monitoring plan before the end of 2019. Remedy implementation, delayed by permitting issues, is planned for 2020. On March 2, 2020, the final design report (v4) was approved by DEQ. The Contractor Work Plan was approved by DEQ on March 27, 2020. In-water cleanup actions began on July 10, 2020 and were completed on October 14, 2020. Approximately 4,700 cubic yards of contaminated sediment were removed and clean cap material was placed over approximately 1.5 acres.

Contamination in the 5-block upland portion of the site is not included in the proposed remedy. Given filling and redevelopment that has occurred, the "direct contact" risk is considered low, and will likely be evaluated in the future. DEQ previously issued a conditional NFA for Block 15, which lies within the historical "footprint" of PGM upland activities.