In the spring of 2010, Phase I of a project began to remediate near shore contaminated sediments in the St. Mary’s River that were left over from the site of an old manufactured gas plant (MGP). Consumers Energy, the owner of the gas plant, dredged approximately 7,500 cubic yards (10,000 tons) of sediment. The sediment was expected to contain polycyclic aromatic hydrocarbons (PAHs) at or above the probable effect concentration of 22.8 parts per million (ppm). Phase II, which started in the fall of 2010, was to remediate and remove impacted sediment in the natural channel portion of the river adjacent to the MGP. The objectives of the entire project were to reduce contaminated sediments that could potentially cause harm to human and aquatic life, reduce the transport of the PAHs from the St. Mary’s River downstream and improve the water quality in the river.
Approximately 19,566 square yards of sediment were dredged from the St. Mary’s River. After being dredged, the sediment was placed on a dewatering pad and mixed with lime and sawdust to help dry the sediment. Once dry, the sediment was transported to Waste Management’s Dafter Sanitary Landfill for disposal. The water that came out of the sediment was collected, treated, tested, and then pumped to the Sault Ste. Marie Waste Water Treatment Plant (WWTP) for disposal.
A total of 57 water samples were collected after dredging to confirm that the area was cleared of the contaminated sediments. Any sampling points that were found to be above the acceptable limits were cover with at least six inches of sand. Approximately 8,859 square yards of clean sand were placed over certain dredged areas.
You can see the full report here.