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<br />R. G. OTTO & ASSOCIATES <br /> <br />5amnlino Locations: Impacts oa surface water quality w~rre <br />evaluated by sampling at two locations in Ralston Creek that <br />bracket the waste rock piles. The first (#301) was loc~sted <br />approsimatelp 3/4 mile upstream of the waste rock piles at the <br />Cotter property line (Figure 4). The second location (~F302) was <br />immediately downstream of the waste rock piles but upstream of the <br />Mine water treatment plant discharge. In each case, tha sampling <br />location was a free-flowing riffle area having a stable (bedrock <br />or coarse rubble! bottom confiquratioa and without any perceptable <br />accumulation of fine sedisents, plant life or other source of <br />sampling contamination. Bridges were installed by USGS staff at <br />each location to lacilitate sample collection during periods of <br />high stream flow. <br />The assessment of waste rock pile impacts on ground water is based <br />oa a comparison of water quality at the upper property line site <br />(#301) with that at a shallow well (location #303) dowaslope of <br />the waste rock piles. The designation of a surface water site as <br />represeatativ: of ground water conditions was made jointly by <br />Cotter and Division staff and is based on as assessment of local <br />geological structures upstream of the waste rock piles. A rock <br />formation of very limited permeability projects to grou.ad surface <br />at a point near the upper Cotter property line (upstream of the <br />waste rock piles). <br />1~ <br />