Upland and In-Water Remediation for the Astoria Marine Construction Company

MFA conducted work from the risk assessment through remedial design and remedial action at a shipyard on the Lewis and Clark River in Oregon. The river is a tidally influenced tributary to the Youngs Bay estuary. Historical activities at the site included ship sandblasting and repair. Contaminants of interest include tributyltin, PCBs, dioxins and furans, metals, and polycyclic aromatic hydrocarbons.

After characterizing upland soils, river sediments, and the potential for transport of chemicals to the river through groundwater discharge and overland flow, MFA evaluated potential risk to human health and the environment. The risk assessment was used to inform the feasibility study, which also included evaluation of hot-spot concentrations, source control measures, and assessment of various remedial technologies and institutional controls. Upland and sediment cleanup alternatives were evaluated for implementability and cost-effectiveness to meet remedial action objectives protective of human health and the environment.

The in-water remedy included focused removal of debris piles, excavation of sediment exceeding hot-spot concentrations in the nearshore areas, and backfilling with clean sand. Sediment with lower levels of contamination, primarily on the tide flats, was remediated through placement of a thin sand layer (up to 12 inches) to enhance the natural recovery.

The upland remedial design for the project included demolition work to prepare for excavation of hot-spot areas and capping with 12 inches of gravel to accommodate proposed security measures for the site, improved stormwater treatment, and the restoration and extension of the dike running through the site. MFA, as the lead project engineer, coordinated with the U.S. Army Corps of Engineers on the Section 408 process for restoration of the existing dike section on site, prepared the Section 408 application, which included a dike design report, safety assurance review plan, and Section 408 checklist response. MFA also provided construction-period services and prepared a construction completion report for certificate of completion.

Under a separate contract to the Oregon DEQ, MFA developed a Performance, Monitoring, Review and Contingency Plan. The Plan establishes the framework for specific performance standards and planned monitoring activities to demonstrate the effectiveness and reliability of the in-water sediment remedy in preventing or reducing human and ecological exposures to Site-related contaminants. Year one monitoring including visual observations, bathymetric surveys, and chemical monitoring is occurring in 2024.