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ensure long-term revegetation success. The Osgood sand reference azea was also quantitatively sampled to provide the revegetation success criteria values for total • vegetation cover and total herbaceous production for the reclaimed azeas governed by the requirements of CDMG Rule 4.15.8. 2002 PRECIPITATION REGIME The climate of the mine and surrounding azea is characterized by a wide temperature fluctuation; from below freezing in winter, to very warm in the summer months. Precipitation in the area is provided by weather systems originating in the Gulf of Mexico and is most frequent and reliable during the spring and late summer months (Table 10). Coors Energy Company has collected precipitation data at the mine for a number ofyeazs. This data represents the most complete record of precipitation from the mine azea. Table 10 presents a summary of precipitation data collected from 1993 through 2002, corresponding with the most recent vegetation monitoring. A review of the data illustrates that precipitation is lowest during the autumn and winter months (October through Mazch) and higher from spring through late summer. The months with the highest average precipitation aze May and June. Based on the 1993-2002 data, average yearly precipitation was calculated. In 2002, precipitation conditions at the mine site were the driest recorded since 1993. Precipitation was significantly lower than average from April through September in 2002. Cumulative precipitation for the January-July 2002 period was 4.28 inches. Total • cumulative precipitation for the period from September 2001-July 2002 was 6.46 inches. This represents a 49 percent decrease from the January-July average of 8.43 inches, a 43 percent decrease from the September-July average, and decreases of 66 percent (January- July) and 59 percent (September-July) from the corresponding periods in 2001. VEGETATION COVER In general, total vegetation cover values were approximately half of their values in the corresponding azeas in 2001. This can be attributed to the significantly lower precipitation during the spring and growing season of 2002. The lack of spring precipitation hampered growth of cool season graminoids and forbs. Continued drought conditions through the growing season reduced growth in the warm season graminoid component. One benefit of the reduced precipitation was the neaz elimination of Bromus tectorum from all reclamation azeas. Kochia scoparia cover was present in greater proportions than in more normal precipitation yeazs, however, this annual forb provides cover and protection for seedling perennials, and tends to disappeaz by the third or fourth growing season, as the perennial component establishes itself. For the purposes of direct comparison, quantitative cover data is present (Table 11) for the 1995 and 1997 reclamation azeas (1998-2002), the 1998 reseeded or interseeded areas (1999-2002) and the Osgood sand reference azea (1994-2002). • Coors Energy Company Page 16 2002 Revegetation Monitoring Report