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Precipitation in the area is provided by weather systems originating in the Gulf of Mexico <br />. and is most &equem and reliable during the spring and late summer months (Table 12). <br />Coors Energy Company has collected precipitation data at the mine for a number of years. <br />This data represents the most complete record of precipitation from the mine area. Table <br />12 presents a summary of precipitation data collected from 1993 through 2003, <br />corresponding with the most recent vegetation monitoring. A review of the data <br />illustrates that precipitation is lowest during the autumn and winter months (October <br />through March) and higher from spring through Tate summer. The months with the <br />highest average precipitation aze May and June. Based on the 1993-2003 data, average <br />yeazly precipitation was calculated. <br />Calendaz year 2003 precipitation levels were very close to average levels. Precipitation <br />was neaz average in September, October, and November 2002, significantly below the <br />norm in December 2002 and January 2003, significantly above the 10.yeaz monthly means <br />from February through May 2003 and moderately to significantly below average for the <br />remainder of the 2003 growing season. Total precipitation for the first eleven months of <br />2003 was 11.82 inches. Cumulative precipitation for the January-July 2003 period was <br />10.24 inches. Total cumulative precipitation for the period from September 2002-July <br />2003 was 12.58 inches. Compazed to their wrresponding averages, these values represent <br />a five percent decrease from the yearly precipitation mean (corrected for 2003 <br />precipitation), a 19 percent increase from the January-July average of 8.59 inches, a nine <br />percent increase from the September-July average, and a 239 percent (January-July) and <br />• 194 percent (September-July) increase from the corresponding periods in 2002. The <br />precipitation regime for this year (2003) favored eazly growth of cool season graminoids <br />and some annual forts. Dry conditions during the mid-summer months to some extent <br />inhibited the growth of the warm season component of both the reclamation areas and the <br />reference area. <br />4.2 VEGETATION COVER <br />In general, total vegetation cover values were approximately double their values in the <br />corresponding areas in 2002. This can be attributed to the significantly greater <br />precipitation during the late winter and spring of 2003. The spring precipitation promoted <br />growth of cool season graminoids and forts, particularly graminoids. Reduced <br />precipitation from June through August reduced growth in the warm season graminoid <br />component. Unlike the 2002 drought year, late winter and spring precipitation this year <br />promoted vigorous growth of the early annual grass Bromus tectorum in all reclamation <br />areas and the Osgood sand reference area. Interestingly, relative cover values for Bromas <br />tectorum in all azeas remained within the range of cover fluctuations observed over the last <br />decade. Other cool season species that benefited directly from the precipitation regime <br />included the Agropyrort species in the reclamation areas and SBpa viridula in the reference <br />azea. Stipa viridula relative cover in the Osgood sand reference area increased 212 <br />percent from 2002, and reached the highest relative cover value in the ten years of <br />monitoring we have undertaken. Perennial cool season graminoid representation increased <br />. dramatically this season. Increases in the sum of all cool season graminoid relative cover <br />Coors EnarWr Company Paga 18 <br />2008 RevegaWtbn Monitoring Report <br />