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at the mine over the precipitation season important to the 2011 growing season would have <br />been significantly below average. <br />Cumulative precipitation for the September- December 2010 period was 1.15 inches, or 61.8 <br />percent below the average for those months (3.01 inches). <br />Cumulative precipitation from January through July 2011 was 12.22 inches, reflecting an <br />amount 144.9 percent above average precipitation for that time period. <br />2.2.2 Vegetation Cover <br />Vegetation cover was estimated by the use of the point- intercept method. An ocular point <br />frame (ESCO Associates) was used to minimize instrument error and maximize precision <br />and observer accuracy. Cover transects were 25 meters in length, with two sample data <br />points collected at 1.0 meter intervals along the transect on opposite sides of the transect <br />centerline, 1.5m apart. Transect direction was established randomly through the use of <br />computer generated random directions (0- 360 °). In no event were transects allowed to <br />extend within ten feet of revegetated area boundaries to minimize impacts from "edge effect." <br />For statistical purposes, each cover transect (comprising 50 data points) served as a sample <br />unit. Data points recorded the first vertical "hit" on vegetation (above or below the <br />instrument), soil (bare ground), rock, litter, or cryptogamic crust. Subsequent "hits" on <br />vegetation (prior to interception of the ground) were also recorded. Cover data were recorded <br />and reported by individual plant species. The first interception was used to calculate total <br />vegetation cover values. Additional interceptions were used to calculate relative cover of <br />individual plant species and lifeforms. The quantitative cover data also provided the basis for <br />calculation of species composition and relative importance. <br />2.2.3 Species Composition <br />Species composition information was derived from quantitative vegetation cover data. <br />Relative cover information provided a basis for evaluation of the importance of each <br />encountered plant species and lifeform and for comparison to the final revegetation success <br />criterion. The table (page 13) presenting data summaries for total vegetation cover for each <br />area sampled also contain the relative cover by species, and a column depicting the numerical <br />ranking of each species by relative cover within the area. <br />2.3 SAMPLE NUMBERS /SAMPLE ADEQUACY <br />For the purposes of this study, total vegetation cover sampling was undertaken to sample <br />adequacy for each sampling unit with a minimum of fifteen (15) samples. Parameter testing <br />occurred at the one -sided 90% confidence level. Comparisons between sample mean <br />parameter values and the revegetation success standard assume that the sample mean value <br />accurately represents the population mean in all cases. <br />The following formula was used for sample adequacy calculations: <br />Coors Energy Company Keenesburg Mine Page 3 <br />2011 Vegetation Sampling: Phase III Eligible Areas <br />