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Coors Energy Company: Keenesburg Mine <br /> Technical Revision 47 <br /> Modification of Reclamation Success Standards <br /> The herbaceous production standard uses the previous 11 month's precipitation (September— <br /> July) to predict the success standard for any given year. For example, the 2019 standard was <br /> calculated for herbaceous biomass production using the September 2018 through July 2019 <br /> precipitation (11.4 inches) in the approved predictive equation: <br /> Herbaceous Production Standard= 0.4666 * (11.4)2.1405 = 85.2 g/m2. <br /> Revegetation is considered successful if the biomass production is at least 90% of this standard <br /> (85.2 * 90% = 76.7 g/m2). Because the herbaceous biomass production data are not separated by <br /> species, we cannot determine the exact production of warm versus cool season grasses; however, <br /> we can estimate this value using the relative cover data and published values for the maximum <br /> height of each grass species at maturity (USDA, NRCS 2019). <br /> The most important component of the plant biomass for determining nutritional value is crude <br /> protein content. Published crude protein data for each species was used to estimate the average <br /> annual crude protein percentage. In some cases,published data were available for all months of <br /> the year, but in other cases, data were only available for some months. Using the published data, <br /> a logarithmic trend line was found to have the best fit across all species (R2 = 0.74, Figure 1). <br /> The available data was plotted for each species and a species-specific logarithmic trendline was <br /> used to estimate the protein in the other months (R2 ranged from 0.74 to 1). This process was <br /> completed for all perennial grass species observed in the reclamation areas in the past two years <br /> (2018 and 2019) as well as those species observed in the last two years of monitoring in the <br /> Osgood Reference Area(2003 and 2004, Table 5). <br /> Figure 1: Best Fit Trendline for Published Crude Protein Data for All Species <br /> 25 <br /> R2 (Y74 i 6 <br /> 20 <br /> i5 <br /> a� i <br /> 0 <br /> A M J J A S O N D J F M <br /> Month (Apr...Mar) <br /> 6 July 2020 <br />