Limnology and remediation of two proximal pit lakes in Northwestern Ontario

Abstract

Two adjacent pit lakes, Caland and Hogarth, were formed after the closure and subsequent flooding of the Steep Rock Iron Mines near Atikokan, Ontario, Canada. They were examined to predict flooding patterns, outflow location, and water quality of the pit lakes when they eventually flow into an adjacent river system. The use of wetlands to remediate of the pit lakes was also examined. Models generated using Arc View v. 3.0 accurately predicted the joining of two pit lakes (Hogarth and Roberts). It also projects the most likely location at which outflow into the Seine River system will occur. While water chemistry varies over time, Cr, and Cu were predicted to reach levels exceeding the guidelines for the preservation of aquatic life in Canada before outflow occurs. Also, Mn, S, SO4, and TDS will likely exceed the levels defined as safe for human consumption. A model incorporating the past and present depths of the oxygenated freshwater lens present on the surface of Caland pit lake predicted that as the lake fills, the depth of this lens will decrease logarithmically. This will seriously impact the operation of a commercial rainbow trout farm situated in Caland. Wetlands may be a practical means of remediation of the water contained within these pit lakes. Of the four plant species examined, Carex sp. was able to concentrate the greatest amounts of S, as well as Al, Cu, Fe, Ni, Sr and Zn. The former west arm of Steep Rock Lake is a likely location for treatment wetlands to be established. This is because it is strategically located between the Seine River and the predicted flood out point. In addition, its large surface area enables it to treat a sufficiently large volume of water to make it practical.