EMR conducted a CERCLA-compliant remedial investigation/feasibility study under the Native American Lands Environmental Mitigation Program. Work completed included an historical/records search, geophysical survey, and development of work plans. The goal of the project was to determine if approximately 1,456 barrels of previously classified munitions deposited by the US Army into Lake Superior between 1945 and 1962 posed a threat to human health and the aquatic ecosystem. The barrels originated from the Twin Cities Army Ammunition Plant in Minneapolis and were known to contain timing devices, munitions, and other unknown waste. EMR surveyed 96 square miles of munitions potentially presenting explosive hazard affected area using side scan sonar, sector scan sonar, and a remotely operated vehicle (ROV). Results from the geophysical survey were used to define the project boundaries and to identify three primary dumping areas.
The plans developed for the barrel recovery phase detailed barrel recovery and associated sampling at depths from 100-450 feet deep using ROVs. Details for the barrel encapsulation and unexploded ordinance staging and testing were covered. Analyses of barrel contents, sediment, and lake water focused on PCBs, POL, and metals.
Work conducted during the barrel recovery phase included recovering, sampling, and properly disposing of randomly selected barrels. In conjunction with barrel recovery and sampling operations, lake water and sediment samples were collected from around the barrels to determine if any contaminants had leaked into the environment. Water and sediment samples were collected outside the immediate project area to assess background contamination from other sources. Samples were analyzed by an independent, accredited laboratory for a wide range of chemical constituents.
Red Cliff Band of Lake Superior Chippewa in Cooperation with US Army Corps of Engineers, Omaha District
Western Arm of Lake Superior, WI/MN