Since the early 1900s, Milltown Dam had been retaining heavy metals that were being transported by the Clark Fork River from large mining communities upstream. In 1981, elevated heavy metal quantities were detected in residential wells in Bonner, Montana, which ultimately led to the identification, remediation, restoration, and redevelopment of the Milltown CERCLA Site. After more than 20 years of study and litigation, reclamation work began on the Milltown CERCLA site on June 1, 2006 to remove more than two million cubic yards of contaminated sediments and the dam itself.
Since the project began in 2006, DJ&A has been providing a variety of engineering, surveying, natural resource, and geotechnical services in support of this CERCLA site reclamation, one of the largest such sites in the country. In terms of the environmental support, DJ&A managed all of the environmental permitting requirements associated with the design, development, and construction of the Milltown State Park. Permitting requirements for the state park required extensive agency coordination involving: MT Department of Environmental Quality, Missoula County Floodplain Department, MT Fish, Wildlife & Parks, US Army Corps of Engineers, MT Department of Natural Resources, US Fish & Wildlife Service, and MT Department of Natural Resources.
- Site inspection and survey
- Reclamation design support
- Channel stabilization
- Community relations planning
- Contaminated sediment surveys (bathymetric and LiDAR)
- CERCLA site redevelopment
- Design for multiple deep-foundation, sheet pile retaining walls to support the removal of contaminated sediment that had accumulated in areas behind the dam
- Design of earthen embankments and rock riprap
- Measured bank channel stabilization
- Controlled monitoring surveys during the drawdown of the reservoir
- Site restoration to verify contaminated sediment quantities
- Hydraulic and hydrologic analysis
- Stream bank stabilization and geotechnical investigation
Community relations planning was a major component to this project and DJ&A was honored to lead this effort in regards to the redevelopment of this CERCLA site, which resulted in the 500+ acre Milltown State Park, which opened to the public in June of 2018.