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Frequent bedrock outcrops were identified on the west side of <br /> the valley. The slopes of this valley side are steeper than on the east <br /> side and much of the ground surface consists of exposed bedrock. Col- <br /> luvium, where present, is very thin and loose and it is generally less <br /> than 6 inches deep. The soil may be thicker in collection areas at the <br /> mouth of larger gullies. The bedrock outcrops are formed by mostly <br /> gneiss or granitic rocks; most of the rocks are very hard and apparent- <br /> ly highly resistant against weathering. <br /> During our mapping program, attention was paid to any potential <br /> stability problems not related to mining activity in the area. The <br /> study area was carefully inspected and checked for any signs of potential <br /> stability problems such as old landslides, rockfall areas, potentially <br /> unstable zones, etc. Aerial photographs made available by Cotter <br /> Corporation were very helpful in supporting the field mapping. No traces <br /> traces of larger scale stability problems such as landslides or rock- <br /> falls that might endanger the stability of the waste piles in the <br /> future were found. The area carries traces of rockfall of a minor <br /> scale and there are traces of erosion on the_slopes._ It iS the engineer <br /> ing geologist's opinion that none of these features can influence the <br /> existing or future stability of the waste piles unfavorably. <br /> 3.2 Ground Water <br /> Ground water conditons have not been studied in any detail as <br /> they have very little influence on the stability of the existing and <br /> future waste piles. According to previous studies performed for Cotter <br /> Corporation by WATEC (Anticipated Post-Mining Hydrology of the Schwartz- <br /> walder Mine, Jefferson County, Colorado, Appendix E-2 of the 1977 Permit <br /> Application) , there are two aquifers identifiable in the Schwartzwalder <br /> Mine area; Quaternary alluvium of Ralston Creek and the Idaho Springs <br /> Formation aquifer. Of these two, only the alluvial aquifer has any <br /> importance for the stability of the waste piles. However, potential <br /> - 9 - <br />