Aberdeen Mill Wetlands Restoration/Mitigation & Mitigation Monitoring

  • Sierra Pacific Mill on the Chehalis River, near Aberdeen
  • Chehalis River mitigation site
  • Elliott Slough mitigation site Year 6 monitoring
  • McNeal mitigation site Year 5 monitoring

Confluence provided permitting assistance for the construction of an expanded wood-manufacturing facility in Aberdeen, WA. Work included field surveys on over 100 acres of the project site to delineate wetlands, identify mitigation opportunities, and evaluate fish and wildlife habitat. Confluence staff developed detailed plans to rehabilitate wetlands along the Chehalis River and in Elliott Slough to mitigate for wetlands filled as part of the project, prepared a wetland maintenance and monitoring plan, coordinated with permit agencies, completed a biological assessment for compliance with the Endangered Species Act, and oversaw installation of the designed wetlands features.

The project included planting 355 trees and 1,270 container shrubs along 820 linear feet of the Chehalis River, and 821 trees and shrubs and 275 live cuttings on more than 15,000 square feet of Elliott Slough wetlands. Poor soil conditions required addition of soil amendments, including topsoil, organic compost, and mulch. Confluence staff performed all 5 of the required years of monitoring at the Chehalis site, summarized monitoring results in annual reports, and oversaw maintenance to ensure the plants developed into a properly functioning shoreline ecosystem. The mitigation area was deemed a success by the U.S. Army Corps of Engineers (Corps).

During final year of monitoring at the Elliott Slough site, a local public utility district removed all vegetation. To compensate, Confluence was contracted to evaluate other properties owned by Sierra Pacific Industries for mitigation opportunities. A new site was identified (McNeal site), and Confluence prepared the mitigation plan and coordinated with the Corps on moving the mitigation area to a new location. In 2016, Confluence provided oversight during construction of new mitigation area has conducted yearly monitoring of the site.

Project Location
Aberdeen, Washington

Sierra Pacific Industries

Project Timeline
Ongoing since 2008