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3. OPERATION PLAN MAP The Division has still not received a copy of BRHIBIT $, MINING PLAN, revised 11/13/94 and referenced in your 11/22/94 response. Please provide this information. 4. PIT HIGHWALL STABILITY AND RECLAMATION After reviewing DGMC's response to this portion of the adequacy review, the Division performed a follow-up review of correspondence associated with the previously approved amendment (no. AM-001) for this operation. This was the first amendment made to the original application end allowed expanded surface mining operations to be undertaken at the site. Based on reclamation commitments made by the permittee in the review documents for this previous amendment, it does not appear that the Division can approve the applicant's proposal under amendment no. AM-002 to leave the open pit highwall areas to a 1:1 slope during final reclamation. A portion of DGMC's 11/22/94 response contained an incorrect statement to the effect that the existing approved permit as amended allows leaving the exposed highwall areas at a slope of 45-50 degrees. In reality, this was not the final approved reclamation scheme worked out between the Division and the permittee during the final stages of the review period for amendment no. AM-001. The proposal to leave the highwall at such a steep slope resulted in several review comments from Division staff at the time due to our concern for long term stability of the exposed highwall area. Resolution of this concern resulted in the applicant committing in a review response letter dated March 13, 1988 to "backfill the open pit from the toe of the bench to the crest of the pit wall. However, in order to meet the 2:1 slope specifications of MLRD, some pit wall may not be backfilled to the crest. The operator will commit to backfilling to at least 10 ft. of the crest of the pit wall and maintain a 2:1 slope". This commitment is a part of the existing approved permit and represents a level of reclamation quality that, in accordance with current Division policy, cannot be lowered through subsequent revisions or amendments. Leaving the area at a steeper slope than what is presently approved will result in potentially less stable slopes, a greater potential for erosion and loss of replaced topsoil, and a greater potential for failure of revegetation efforts. Additionally, information in another part of DGMC's 11/22/94 response which indicates the presence of highwall instability "where vein structures appear, and where portions of the Marl Member of the strata are exposed", further affirms our belief that specific measures such as highwall backfilling to a reasonable slope are necessary in order to ensure adequate stability. 3