2008-04-15_REVISION - M1980244 (256)

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~~ ,' SMITH WILLIAMS CONSULTANTS, INC. • 2.0 Site Description 2.1 Location and Topography The existing Cresson Project VLF is located in Arequa Gulch in Teller County, Colorado. Phase 5 of the VLF will lie to the north and east of the existing VLF in the upper Arequa Gulch area, against Squaw Mountain and the AGOSA, as shown on Drawing A100. Portions of the Phase 5 VLF area have been disturbed by previous mining activities. Manmade structures within/near the footprint of the proposed project site include power lines, gas lines, other utilities, underground mine workings, and surface mine workings, as shown in Drawings A100 and A120. All vegetative cover, organic soils, and structural materials associated with the manmade structures will be removed or relocated prior to or during subgrade preparation. _ 2.2 Climate Original climate data for the project site were documented in Amendment No. 6 to Permit M- 1980-244 (CC&V 1993). These data have since been augmented with available site data collected by CC&V. In addition, gaps within the climate data have been filled using climate records from the Western Regional Climate Center (WRCC), as detailed in Appendix G. As part of this design, Smith Williams combined and incorporated_the climate data to develop a consistent precipitation database that spans_from 1966 through 2006. The precipitation, data for each month are presented in Appendix G. The monthly average and standard deviation precipitation values were then recomputed incorporating all of the precipitation data; they are summarized in Table 1. The average yearly precipitation, including snowfall, is 18.4 inches. The 100-year/24-hour design storm event was quantified as 3.5 inches from the 1973 NOAA isopluvial chart. This 3.5-inch value was mutually agreed on by the DRMS and_CC&V during review of Amendment No. 7 to Permit M-1980-244. At the time Amendment No. 6 was prepared, evaporation data were not available for the Victor or Cripple Creek stations. Therefore, a statistical analysis of pan evaporation data collected at nine similar high-elevation recording stations in the State of Colorado was performed. This analysis. resulted in an average annual lake evaporation of 36.8 inches. Since Amendment No. 6, evaporation data have been collected by CC&V from August 1994 to November 1999. The daily evaporation data provided by CC&V are presented in Appendix G. The average monthly evaporation data measured by CC&V from August 1994 through November 1.999 are S:\PROJECTS\1125 CC&V PHASE 5 VLF1H2 - DESIGNVIREQUA VLF\VLF PHASE 5 FINAL REPORT V2.DOC 13