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Memorandum <br />To: Kent Gorham <br />CC: Dan Hernandez V file <br />From: Janet Binns <br />Date: 11 /2/2004 <br />Re: Rimrock Mine 2004 Vegetation Sampling Report, C-1989-074 <br />I have completed the 2004 Vegetation report for Rimrock Mine. Vegetation sampling was conducted <br />by Emily Waldron and Janet Binns of Colorado Division of Minerals and Geology on July 6 and July <br />7, 2004. The July 2004 Rimrock inspection report contains details of the Divisions observations. <br />The revegetation standard for the Rimrock Mine include <br />Cover: 41 <br />Production: 514 lbs/acre (air dry weight) <br />Sbrub Density: 0 <br />Species Diversity: At least three perennial grass species, each contributing at least 3%, but not <br />greater than 60% relative cover. At least one of these species will be a warm <br />season grass and at least one shall be a cool season grass. <br />Live vegetative cover measured in July 2004 was 37.7%. This value is greater than 90% of the <br />reclamation success standard with a 90% confidence interval. The reclaimed azea cover meets the <br />cover standard and achieved statistical sample adequacy. <br />Live herbaceous biomass measured 931.9 Ibs/acre. This value is well in excess of the reclamation <br />success standard for productivity, however, statistical adequacy was not achieved. The Division <br />analyzed the 2004 productivity data using the reverse null hypothesis. The reverse null hypothesis <br />test found the 2004 productivity data met the reclamation standard. <br />Sixteen plant species were represented during the reclaimed area vegetation cover sampling. Eight <br />species measured greater than 3% relative cover. No species was present at greater than 60% relative <br />cover. Four species were perennial cool season grasses, and two species were perennial warm season <br />grasses. The diversity standazd for the Rimrock mine was achieved. <br />Please refer to page 22 of the Colorado Division of Minerals and Geology Guideline Reeardine <br />Selected Coal Mine Bond Release Issues, dated April 18, 1995, for the T-test formula, and page 21 of <br />the same document for the sample adequacy formula. <br />