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<br />DEPARTMENT OF NATURAL RESOURCES <br />David H. Getches, Executive Director <br />MINED LAND RECLAMATION DIVISION <br />DAVID C. SHELTON, Director <br />Hicherd D. Lemur <br />Governor <br />DATE: Apr11 2, 1984 <br />T0: Susan Mowry <br />FROM: Jim Pendleton <br />RE: Trapper Mini <br />~~~~ <br />pulatlon Responses <br />Pursuant to your request, I have reviewed Trapper Mining's recent submittals <br />made 1n response to the requirements of Stipulation No. 3, placed upon their <br />permit for the Trapper Mine. <br />Overburden Swell Verification <br />The operator has submitted a report presenting the results of a required <br />survey analysis of actual overburden swell factors within the regraded areas <br />at the Ashmore, Derringer, and Enfield Pits at the Trapper Strip Mine. The <br />detailed survey study determined that the average swell factor throughout the <br />Trapper Mine was 24.6X. Based upon results of this thorough survey-based <br />analysis, I concur with Trapper Mining's conclusion that it is appropriate to <br />consider their assumed 25X swell factor to be actual. Further, I recommend <br />that we delete the requirement for annual completion of a survey swell factor <br />analysl5 at the Trapper Mtne from their current permit. We should, however, <br />continue to require the originally stipulated annual submittal of a <br />post-mining topographic contour map for areas regraded at the Trapper Mtne. I <br />no longer believe it is necessary to require submittal of both the map and the <br />swell factor analysis. <br />Map A -"1983 Post-Mining Contour Map" <br />I have compared Map A, "1983 Post-Mining Contour Map", with Map M12, the <br />original permit application "Post-Mtning Contour Map". In my opinion, the <br />projected and actual post-mining topographic contour appears to correlate <br />well. The operator appears to be achieving the Improved character of the <br />planned post-mining topographic configuration for the mined areas at the <br />Trapper Mine. <br />The areas regraded during 1983 involve portions of the cross-sectioned <br />drainages of Johnson (Enfield Ptt) and Buzzard (Derringer Pit) Gulches. I <br />recommend that you have one of the surface hydrologists on our staff review <br />these sections of the regraded topography, in order to ascertain their <br />compliance with the appropriate permit requirements. <br />/cd <br />cc: Brian Munson <br />Doc. 0459E <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (30~) 866-3567 <br />