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<br />TRAPPER TOPSOIL SALVAGE PROPOSAL <br />Current Topsoil Salvage Practices <br />In Section 4.9.1 of Permit C-81-010 Trapper commits to replacement of 12" of topsoil for <br />rangeland and 18" of topsoil for cropland. The 12" and 18" topsoil replacement depths on <br />rangeland and cropland, respectively, were considered optimum for successful plant com- <br />munity establishment by Dr. Ed Redente of Colorado State University based on site specific <br />studies he and his associates conducted at Trapper Mine. It has become evident in recent <br />years however, that Trapper has been salvaging excess topsoil. The net result has been an <br />ever increasing topsoil surplus. <br />A recent investigation of Trapper's topsoil surplus determined that Trapper has been stripping <br />all dark-colored topsoil to a depth where the soil color turned abruptly to a lighter shade. <br />Our intent is to salvage only A and upper B horizon topsoil, as approved by our permit and <br />described in Section 4.9.1. Evaluation of available topsoil data revealed that, in fact, <br />Trapper's topsoil stripping to a definite color change has resulted in salvaging not only A and <br />upper B horizon material but also all lower B horizon soil to the C soil horizon boundary. <br />Attached Table 1 illustrates this point. <br />Table 1 compares weighted average results of 980 topsoil depth grid samples taken on 250' <br />centers from 1988 to 1992 th Derringer, Ashmore and Hawken pits to weighted average <br />horizon depths of soil series mapping units described for Trapper soils in Section 2.4 of C- <br />81-010. This comparison demonstrates that the weighted average depth from the topsoil grid <br />samples (19.7") is virtually identical to the weighted average sum of A and B horizon soil <br />profile depths calculated from soil series mapping unit descriptions (19.4") <br />Recent average pre-mining topsoil salvage depths at Trapper are in close agreement with the <br />average combined A horizon plus B horizon soil depths presented in Table 1. The following <br />average topsoil depths were salvaged from 1990 through 1993. <br />Ave. Salvage <br />Year De th in <br />1991 23 <br />1992 21 <br />1993 20 <br />It is logical that average topsoil stripping depths would be slightly more than the 19" depths <br />given in Table 1, as one to several additional inches of C Horizon topsoil are typically picked <br />up by a scraper operator each time a topsoil lift that exposes a definitive soil color change is <br />removed. <br />Proposed Tonsoil Salvage Plan <br />It is obvious from the preceding topsoil analysis that the key to balancing Trapper's topsoil <br />salvage and replacement programs is to stop stripping to a soil color change and begin strip- <br />