Former Custom Plywood Mill Interim Action Cleanup
Hart Crowser worked for the Washington State Department of Ecology to remediate and restore the Custom Plywood site under the state’s Puget Sound Initiative. The site remediation program focused primarily on extensive wood waste deposits as well as petroleum hydrocarbons, metals, and dioxin contamination derived from 80 years of continuous use. Hart Crowser developed a phased interim action approach under the state’s Model Toxics Control Act (MTCA) and led cleanup actions and restoration of upland, intertidal, and shallow subtidal habitats on the site. The Phase 1 upland remediation (2012) involved removing legacy structures and contaminated soils above ordinary high water (OHW) as well as constructing a 12,000-square foot wetland mitigation area and stormwater bio-swale. Hart Crowser prepared the Interim Action Work Plan package (RI/FS/CAP/EDR), prepared plans and specifications, provided procurement support to Ecology, and led construction oversight.
Phase 2, the intertidal and selected subtidal remediation, included restoration of the shoreline, dredging over 4.5 acres of contaminated sediments, and removing over 1,000 creosote-treated piles. Hart Crowser provided planning and permitting documents, including the IAWP (CAP/EDR), Joint Aquatic Resource Permit Application (JARPA) package, and the biological evaluation (BE). We also provided design and construction oversight of intertidal/nearshore excavation and subtidal dredging of wood waste- and dioxin-impacted sediment, and removal of over- and in-water structures and piles. The final phase includes innovative delivery of a thin-layer cap to remediate dioxin-impacted sediment within approximately 8 acres of sensitive eelgrass habitat.
The cleanup employed a combination of traditional and new cleanup approaches to reduce the highest pockets of toxic risk and take advantage of the natural tendency of the environment to heal itself. The extent of the cleanup is staggering: removal of 2,500 creosote-soaked piles and 2,600 tons of construction debris; excavation of more than 75,000 tons of toxic soil and sediment; construction of 12,000 square feet of new wetlands and habitat; and restoration of 4,400 feet of beachfront. These restored areas will stabilize and expand over time, creating new habitat for shellfish, aquatic plants, and terrestrial birds and mammals.
- Developed ecosystem based enhancement concepts that bring high-value habitat back to the site fostering ecological recovery on multiple scales and for multiple species that now are using the nearshore area.
- Performance monitoring shows that the created habitats (wetlands, shoreline, eelgrass habitat) are performing as expected and in many cases at a higher level that predicted.
- Our pilot study to investigated the feasibility of applying a thin layer cap in sensitive eelgrass habitat as a remedial alternative. Results clearly indicated a defensible preferred alternative that was not only prescriptive but also feasible to employ at a larger scale.