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• 6.4.20(13)(b)(i) <br />Monthly precipitation totals for this region have been collected, as reported by NOAA, for: <br />• Georgetown, Clear Creek County, CO for a period of 1948 - present <br />• Idaho Springs, Clear Creek County, CO for a period of 1948 -1974 <br />This data is attached within the appendix of this Exhibit T. <br />6.4.20(13)(b)(ii) <br />Average windspeed and prevailing direction have been collected for Boulder/Jeffco Airport ... the closest station. <br />This data is attached within the appendix of this Exhibit T. <br />6.4.20(13)(b)(iii) <br />Monthly temperature data for this region has been collected, as reported by NOAA, for Evergreen, Jefferson/Clear <br />Creek County, CO for a period of 1971-2000. This data is attached within the appendix of this Exhibit T. <br />6.4.20(13)(b)(iv) <br />The pan evaporation rate for the area (as reported by the Western Regional Climate Center) ranges between 35.5 - <br />40.5 inches annually. This data is attached within the appendix of this Exhibit T. <br />6.4.20(14)(a-e) <br />The site is completely composed of crystalline Precambrian rocks, i.e. gneisses and schists, and tertiary intrusive <br />rocks such as quartz monzonites overlain by 0-24" of unconsolidated material. Base geologic information can be <br />found above in 6.4.20(8)(c), an excerpt from USGS Bulletin 1208, Economic Geology of the Idaho Spring District <br />- Clear Creek and Gilpin Counties. Colorado, Moench, Robert H. and Drake, Avery Ala, Jr., 1966. <br />The pre-existing abandoned mine waste rock to be processed consists predominately of silica & alumino silicate <br />• minerals. The sand portion is composed of vein type material such as quartz gangue and quartz monzonite <br />porphyries with some of the surrounding wall rock composed of metamorphic gneisses. The clays are formed from <br />altered wall rock and feldspars. <br />The potential for acid formation exist because of the weathering of sulfide minerals present, consisting of iron <br />sulfide (FeS2 or pyrite) and copper iron sulfide (CuFeS2 or chalcopyrite). These are the minerals to be removed, <br />along with the trace associations of precious metals and heavy metals that occur. This is the material collected in the <br />table and flotation concentrate for sale to a third party for further treatment and refining. <br />The acid formation occurs through a natural weathering phenomenon of the sulfide minerals, in this case pyrites, <br />with air and rainwater. This process occurs naturally underground as a natural geologic event. The problem in this <br />mining district is that the weathering process has been accelerated because the rock containing these minerals has <br />been brought to the surface and deposited in concentrated piles. With increased air transfer and increased contact <br />with rainwater, the accelerated oxidation creates an acidic run-off more quickly that harms the environment. <br />The basic steps in this weathering chemistry can be seen as follows: <br />• Step one: The pyrite oxidizes upon contact with air and water. <br />Fe+2 + 1/4 OZ + W --> Fe+3 +1/2 H2O <br />• Step two: Iron oxidizes to ferric iron. <br />FeS2 + 7/2 O2 + H2O --> 2SO4 2 + Fe+2 + 2H' <br />• Step three: Precipitation occurs with ferric iron to ferric hydroxide. <br />0 Fe+3 + 31-120 --> Fe(0IT)3 + 3H+ <br />23