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TR-62 Preliminary Adequacy Comments <br />In response to the December 9, 2005, Preliminary Adequacy Review for TR-62, the following <br />comments are provided. <br />During initial permitting of the Colowyo Mine in the early 1980's, the Division had <br />questioned whether the intensity of baseline soil sampling and mapping was adequate to <br />allow for sufficiently accurate estimates of available soil volumes for operational and <br />reclamation purposes. Operator azgued that data was adequate (see page 2.04.9-16), but <br />agreed to monitor soil balance and provide soil balance reports on an annual basis, as a <br />means of confirming the adequacy of the baseline information. Apparently, the Division <br />approved deletion of the annual soil balance reporting in association with Permit Renewal <br />RN-1, in 1987, based on review of the monitoring data that had been provided. <br />Within this (TR-62) revision application, Operator is requesting to reduce the topsoil <br />replacement thickness from 18 inches to 8 inches, based on comparison of surveyed soil <br />stockpile volumes to disturbed acreage not yet topsoiled. The evaluation indicates that <br />topsoil in stockpile is sufficient to allow an average replacement thickness of only 8.48 <br />inches. <br />Please provide an explanation of the factors that resulted in the current shortfall (as <br />compared to original projections). Were original estimates of soil availability <br />inaccurate? Were inadequate "quality control" practices employed to ensure and <br />document that all suitable topsoil is salvaged from the various soil types, and that an <br />"approximately uniform" soil thickness is replaced, in accordance with permit <br />requirements? What are the current practices for ensuring compliance, and what <br />changes have been implemented or will be implemented to ensure that modifications <br />of such magnitude will not be required in the future? <br />Response: We are aware of this history. In hindsight, we believe that the original soil survey <br />overestimated the quantity of topsoil available and was not detailed enough to accurately <br />define the resource. Since the end of 1990, the disturbed area has more than doubled <br />(from 1, 809 acres to about 3, 840 acres as of December, 2005), while the amount of area <br />reclaimed during that time has significantly increased as well (1,153 acre increase). <br />Essentially all of these reclaimed lands through the year 2004 were reclaimed with an 18 <br />inch topsoil replacement depth, which reduces the quantity of resource available. <br />Quality control measures exist to ensure that all suitable Topsoil in advance of mining <br />has been salvaged. In places, stopping depths have exceeded 12 feet in depth. <br />Replacement depth is also carefully controlled. While the replacement depth may vary <br />somewhat within an individual reclamation polygon, the average replacement depth for a <br />given reclamation polygon is typically based on either load count or known stockpile <br />volumes and known polygon limits. The average depth is determined by dividing the <br />known volumes by the known area. All topsoil stockpile volumes are based on survey <br />data, and annual changes are updated as they occur. <br />