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The following formula was used for sample adequacy calculations: <br />• (t)2 (s)2 <br />nmin - ---------------- <br />(d Xbar)2 <br />where: nmin = minimum sample size <br />s = sample standard deviation <br />t = the Student's t distribution value at the 90% level (one-sided) <br />d = percent acceptable deviation from the mean (10%) <br />Xbar = sample mean <br />2.4 STATISTICAL ANALYSIS <br />Statistical analysis for the revegetation success criterion of total vegetation cover is required <br />if the value of the sample mean from the reclaimed area is less than 90 percent of the value of <br />the final revegetation success criteria for total vegetation cover or total herbaceous <br />production. <br />Sampling revealed that the mean total vegetation cover for both of the sampling units was <br />greater than that of the final revegetation cover success standard value, therefore no statistical <br />analysis was required. Similarly, total herbaceous production means for the 1985/1986/1987 <br />• and 1995/1997 sampling units significantly exceeded the final herbaceous production <br />criterion value, therefore no statistical analysis was necessary. <br />2.5 SPECIES IDENTIFICATION AND VERIFICATION <br />Species identification was accomplished in the field through the use of plant identification <br />keys (Harrington, 1954, Weber, 1990; Whitson, 1987; Zimdahl, 1990, Stubbendieck, et al, <br />1995). In cases where plant identification was inconclusive in the field, voucher specimens <br />were pressed for lab identification. <br />3.0 RESULTS <br />3.1 QUANTITATIVE EVALUATION: RECLAMATION AREAS <br />3.1.1 1985,1986, and 1987 RECLAMATION AREAS <br />The 1985 reclamation areas encompass approximately 22 acres of reclaimed pit in the north <br />central area of the Keenesburg Mine permit area. The 1985 reclamation area is composed of <br />two parcels (Areas 13 and 22) separated by a north-south haul road corridor. This area is <br />nearly flat with a gentle slope (<2°) to the north and east. Reclamation and coincident <br />revegetation within this area took place in 1985. Replaced soils were sandy in texture. The <br />. revegetation seed mix differed slightly in composition and representation of cool season <br />Coors Energy Company KeenesWrg Mine Page 8 <br />2007 Phase III Vegetation Study