ABSTRACT
Drainage from mineralized Duluth Complex stockpiles located at LTV’s Dunka Mine in northeastern Minnesota contains elevated concentrations of nickel, copper, cobalt, and zinc and has increased metal concentrations in nearby receiving waters to levels up to 400 times the natural background concentrations. These levels exceed water quality guidelines established by the Minnesota Pollution Control Agency (MPCA), and in 1985 the company signed a stipulation agreement with the MPCA which established a timeline for achieving water quality goals. Wetlands located near stockpiles and appearing to offer treatment area for each seepage are typical of many small lowland areas in northern Minnesota and would be associated with any mining area. Based on the estimated lifetimes of the treatment systems, wetland treatment appeared to be a useful mitigation method, but additional test work was needed. Objectives of the tests are to optimize treatment efficiency with flow distribution methods and vegetation types; measure system life; and develop data for application to full-scale treatment systems.
