Saint Louis River Area of Concern - Dock Wall Sediment Investigation – Slip C

The Minnesota Pollution Control Agency (MPCA) and Wisconsin Department of Natural Resources (WDNR) are currently working together to implement a comprehensive long-term plan to delist the Saint Louis River Area of Concern (SLR AOC). Many of the Beneficial Use Impairments (BUIs) in the AOC are linked to the presence of sediment contaminants. Bay West understands the MPCA is overseeing sediment remedial actions at Slip C. Currently, the United States Army Corps of Engineers (Corps) is completing design an engineered cap over the contamination footprint at Slip C; however, a sound navigation and ranging (SONAR) and light detection and ranging (LIDAR) survey in Slip C revealed serval areas of dock wall deterioration resulting in erosion and deposition of backfill material from behind the dock wall onto the Slip C bottom. It is unknown whether the backfill material in these areas is contaminated. If the material is not contaminated, the additional material on top of the cap will only further stabilize the cap. If the material is contaminated, the eroded material will have to be leveled within the remedial footprint prior to constructing the cap. Characterization of the eroded backfill material is required for the Corps to complete the engineered cap design.