REV10252 - Laserfiche WebLink

Home Browse Search

It should be noted that the geotechnical review comments from Allen Sorenson of our Denver Office forwarded to you oa 11/28/94 regarding highwall reclamation did not have benefit of knowledge of commitments made in the review correspondence for amendment no. AM-001. Although Mr. Sorenson indicated that it may be possible to allow highwalls "cut in competent rock, with fractures or fracture seta dipping into the highwall face, and not exceeding 25 ft. in height, to be left as permanent reclamation features", such a scheme would appear to represent a reduction in the quality of reclamation below that approved in the existing permit which calls for 2:1 slopes to within 10 ft. of the crest. In order for the Division to allow any change to the existing commitments, it will be necessary for the applicant to adequately demonstrate that the final highwall area is competent per Mr. Sorenson's criteria, that the proposed grading scheme provides the same level of highwall stability as that committed to in the existing approved permit, that the proposed steeper slopes will be no more erosive than slopes presently approved, that loss of topsoil will not occur, and that an equivalent degree of revegetation success can be achieved. Since it does not appear that such a demonstration of stability can be made prior to exposure of the final highwall without an extensive drilling program to determine bedrock fracture frequency and orientation, it is not possible to predict if the proposed open cut highwalls will be stable. The Division feels that the best course of action available at the present time is to adhere to the existing approved highwall backfilling plan and, at the point in time when the final highwall is exposed, the operator can complete a joint, fracture, and fault mapping program on the face of the highwall and, if it can be demonstrated that the final highwall is sufficiently competent to provide a level of stability equivalent to that provided for in the existing permit, the permit can be revised accordingly. As many reclamation commitments are often worked out and finalized in the review correspondence of a particular permitting action, and this correspondence forms an integral part of the final approved permit application package, the Division suggests that DGMC contact our Denver office and obtain a complete copy of the Incas Mine file, including all correspondence generated during review of the original application and the first amendment made to the original permit. The Division feels it is important that all mine operators who have acquired a reclamation permit via transfer of an existing permit become familiar with all specific requirements of the existing approved mining and reclamation plan. 4