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Larry Routten and Erica Crosby -2- November 3, 1993 within Peak F/ows in Co%rado (U.S. Department of Agriculture, 1984). These mapped numbers are the same as the mapped May to October precipitation values shown in the Precipitation - Frequency At/as of the Western United States. Our permitting work should always use the annual precipitation values mapped within the Precipitation -Frequency At/as of the Western United States. The Peak F/ows in Co%rado values and the Precipitation - Frequency At/as of the Western United States May to October values should not be used. The values used for the GEC design are: 10-year, 24-hour - 3.2 inches 25-year, 24-hour - 3.8 inches 100-year, 24-hour - 4.8 inches. The site location was transferred to the Precipitation -Frequency At/as of the Western United States maps by verifying the basin location relative to the 6,000-foot and 7,000-foot contour lines. Specifically, the basin projects approximately northeast, from the location where the 7,000-foot contour line intersects the southern boundary of Fremont County. This point is located south of Canon City and west of Pueblo. Our previous estimate of 3.8 inches (100-year, 24-hour) was incorrect, and the number resulted from inadvertently locating the site approximately 118 of one inch too far to the north. This mistake occurred due to the rushed conditions surrounding the previous estimate, and is now corrected. Vegetation Tvoe Vegetation types are used to derive the runoff curve numbers. Four sources were used to describe the vegetation types present within the West Pit diversion drainage basin. These sources are: - Map 16; Mine Area Vegetation; Southfield Mine Permit - Rockvale, Colorado, Quadrangle Map - Aerial Photograph No. 162 (10 in.x 10 in.) Flown May 10, 1983. - Soil Survey Map/Photos The Map 16 shows the vegetation communities for the West Pit Diversion drainage basin, to a southern boundary line along the map coordinate N158,000. This includes all of Section 30, Township 20 South, Range 69 West, and most of the north half, Section 31, Township 20 South, Range 69 West. The aerial photograph was used to describe the vegetation types within the south half, Section 31, Township 20 South, Range 69 West, and the southeast quarter, Section 36, Township 20 South, Range 70 West. All three sources corroborate one another for those areas which overlap. The white areas depicted on the USGS Quadrangle map generally correspond with those grassland areas depicted on the Map 16, and in the 1983 photograph. The grassland areas also generally correspond with the soil groups represented by the labels StC and Nd (Figure 5).