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Achievement of Natural Surface Runoff Levels <br />In order to satisfy one of the CDRMS requirements for Phase II bond release, reclaimed <br />areas must be shown to contribute equal or less sediment to the receiving waters <br />downstream than adjacent undisturbed areas. A sedimentology evaluation of the reclaimed <br />areas and adjacent undisturbed areas to assess the projected sediment yield was undertaken <br />using the Universal Soil Loss Equation. The 2020 sedimentology evaluation report, <br />Oxbow Minim, LLC, Elk Creek Mine (C-1981-022), Somerset, Colorado, Phase 11 Bond <br />Release (SL -03), Sedimentology Evaluation is appended to this bond release application. <br />The projected mean sediment yield from the eligible reclaimed areas sampled in 2020 is <br />0.352 tons/acre/year (with individual reclaimed areas ranging from 0.055 to 1.604 <br />tons/acre/year). Projected mean sediment yield from adjacent undisturbed extended <br />reference area is 2.175 tons/acre/year (individual areas ranging from 0.043 to 13.695 <br />tons/acre/year). <br />The results of the USLE calculations illustrate that the eligible reclaimed areas are <br />projected to produce less sediment than the adjacent undisturbed areas. The equation <br />verifies what is expected in this case and also what has been seen at other reclaimed sites <br />in Colorado. Based on the results of the sedimentology evaluation, the reclaimed areas at <br />the Elk Creek Mine qualify for Phase II bond release at this time. <br />Achievement of Revegetation Success <br />Comparison of the reclaimed areas values for total vegetation cover and species <br />composition with the applicable revegetation success criteria indicates whether <br />revegetation has been successful and compliant with requirements for Phase II bond <br />release. CDRMS Rule 3.03.1(2) provides for release of bond, "upon the establishment of <br />vegetation which supports the approved post -mining land use and which meets the <br />approved success standard for cover pursuant to 4.15.8..." The tables below allow the <br />comparison of the parameter values from the 2020 sampling at the reclamation areas with <br />the revegetation criteria to be achieved. <br />The report, Oxbow Mining, LLC, Elk Creek Mine (C-1981-022), Somerset, Colorado, <br />2020 Phase II Bond Release Vegetation Report (SL -03) documents achievement of the <br />applicable revegetation bond release criteria for reclaimed areas and is appended to this <br />application. <br />A summary of the applicable revegetation success criteria and sampled values for 2020 for <br />Phase 11 bond release at the Elk Creek Mine follows. <br />Phase II Bond Release Reclaimed and Revegetated Areas Reclamation Success: <br />Total Vegetation Cover (2020) <br />Demonstration of revegetation success at the Elk Creek Mine for Phase 11 bond release <br />requires that the total vegetation cover at the eligible reclaimed areas meets or exceeds the <br />value of the total herbaceous cover value calculated from the Extended Reference Area. <br />The table below compares the vegetation cover values from the 2020 sampling. <br />........................................................................ <br />Oxbow Mining, LLC Elk Creek Mine Page 6 <br />SL -03 2020 Phase 11 Bond Release Synopsis <br />