PHYSICAL DYNAMICS OF TWO ADJACENT PIT-LAKES

Lakes formed in mine pits continue to be of interest in terms of their water quality and in their use in managing other water quality problems around mine sites. Water quality in these pit-lakes depends on both geochemical and physical processes.

We will describe the hydrology and physical processes observed in two adjacent but contrasting pit-lakes at the Equity Silver Mine site near Houston B.C. These pit lakes have been the subject of a three-year study and the geochemical aspects will be described in companion presentations.

The larger Main Zone pit-lake is 120 m deep and remains oxic and relatively well mixed as a result of sludge discharge through much of the year. In contrast, the smaller Waterline pit of 40 m depth was anoxic and permanently stratified below 10 m. The seasonal evolution of these pit-lakes and the implications for their geochemistry will be described.