080121-08MN006-Sabina Hackett River Project Proposal ... - NIRB

Description of the Existing Environment6.1.10.3 Lake Water QualityLake water quality was measured four times during 2007: May (winter), July, August, andSeptember (Rescan 2008a). Historical data are available from some lakes for the followingperiods: August 2004, July 2005, July 2006 (GLL 2004, 2005, 2006).The 2007 lake water quality program focused on characterizing the potential natural variation inlake water quality with water column depth, season, and geographical location. A total of 28lakes were sampled during 2007. Samples were obtained from different depths with a lake, fromboth winter and open-water seasons, and from lakes lying within a number of differentwatersheds. Two reference lakes, located ~10 km away from potential mining activities, werealso sampled. Data collected during the years 2004-2006 consisted of mainly single surface grabsamples from one time period per year.GeneralIn general, lakes in the area contain extremely clear, low nutrient, low metal water, indicative ofpristine high Arctic lakes. Most lakes have near-neutral waters, with very low hardness andalkalinity. However, naturally high metal concentrations are present in some lakes, indicatingtheir proximity to surface mineralized areas. These lakes can have metal concentrationsexceeding CCME guidelines for the protection of freshwater aquatic life, and can have metalconcentrations 10 to 100 times greater than other lakes in the area.Water Column Depth VariationAs discussed in the limnology section above, lakes in the area fully mix numerous timesthroughout the year (open water season; just prior to freeze up, and during spring ice off). Giventhe mixed nature of the lakes, it would be expected that chemical stratification would not takeplace within a lake, unless there was an input source of a different characteristic water (e.g.,seepage from a mineralized area; sediment influence of overlying water chemistry during winteror times of periodic stratification).However, despite the mixing, a few differences were found with depth in some lakes during thewinter (due to sediment/water interactions) as well as at the beginning of the open-water season(likely due to surface seeps from mineralized areas). During the winter, bottom waters werenaturally elevated in nitrate concentrations in many lakes. This is a natural process, and the mainsource of nitrate to the water column when the water mixes in the spring. Nickel and zincconcentrations were also slightly higher in deep water during the winter in three lakes that weresampled.During the open-water season, lake water quality was generally uniform, with the exception ofthree lakes in July. One lake had very large differences in water chemistry with depth, with lowpH, high Al, Cd, Cu, and Ni concentrations in surface waters (Row Lake; See Rescan 2008a).This lake was obviously influenced by a surface seep. Two other lakes exhibited smaller verticaldifferences, but were also likely influenced by seeps.January 2008 Hackett River Project – Project Proposal Sabina Silver CorporationReport Version B.1 6–18 Rescan Environmental Services Ltd. (Proj. #833-2)