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i <br />• • <br />diversion channel or emergency spillway can be subject to or ~ <br />release erosive velocities during peak flow events that will <br />contribute an excessive sediment load to the stream. Similarly, <br />underdesigned culverts can potentially result in road. failures <br />that cause an influx of debris and embankment material into the <br />channel. The removal of these structures at the end ~'of mining <br />operations will also cause an uncontrolled flow of sediment into <br />streams until revegetation is effectively established. <br />Surface water flow from approximately 396 acres will be im- <br />pounded during mining operations, and subject to evaporation <br />loss. Although this will impact the North Fork of Bolton Draw <br />downstream of mining operations, the acreage represents only six <br />percent of the total Bolton Draw watershed. <br />High sodium absorption ratios characteristic of overburden <br />at the mine site could potentially have severe impacts on both <br />the surface water and ground water resource. Therefore, it is <br />essential that special handling of toxic overburden be imple- <br />i <br />mented so that it will be removed from contact with the water <br />resource. Impacts to surface water quality can be reduced by <br />burying the overburden and by controlling runoff from overburden <br />stockpiles with diversions and erosion controls. The ground <br />water resource, however, will be unavoidably affected by leaching <br />of the replaced, high SAR spoil material. The extent of this <br />impact will be controlled by handling and replacemenit of the <br />spoil material, new infiltration/percolation rates in ghat spoil <br />and establishment of postmining surface drainage ,patterns. <br />Although the extent of sodium contamination has knot been <br />quantified, it is anticipated that both ground water and surface <br />water will show increases in that parameter. Given the small <br />area of the mine site relative to the North Park Basin and the <br />fact that there are no ground water uses immediately down-dip of <br />the mine, these impacts should be reasonable if overburden is <br />correctly handled. <br />-4- <br />