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:. STATE OF COLORA00 qiC HAgD D. LAMM, Govern nr III ~II~I~~II~~II~II • DEPARTMENT OF NATURAL RESOURCES D. Monte Pascoe, Executive Director MINED LAND RECLAMATION 423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567 David C. Shelton August z3, 1982 Director TO: Jim Herron , FROM: Jim Pendleton RE: Review of Po rhorn oaI Plan Submi tal C~ ', Company's Supplemental Subsidence Control Pursuant to your request, I have reviewed the supplemental submittal made by Powderhorn Coal Company for the Roadside/Cottonwood application. With the exception of the few easily resolvable remaining items, I believe that these subsidence control plan portions of the permit are now acceptable: (1) The proposed control plan allows for the retention of protective coal pillars beneath Rapid Creek and Cottonwood Creek. In order to prevent confusion in the future, Map RSOl-02-006 (Exhibit No. 5) should be amended to include a delineation of the boundary of this protective pillar zone. The reconnaissance level alluvial valley floor investigation, recently pre- pared by Kaman Tempo, Inc., concludes that no alluvial valley floors or significant alluvial deposits exist within the area of projected subsidence. Therefore, the applicant should delineate a protective pillar zone boundary which will protect a 50-foot wide corridor centered upon each of Rapid and Cottonwood Creeks. (2) The proposed control plan's justification includes reference to a study by J.F. Abel, Jr., entitled "Analysis of Pillar Failure Second and Third East Panels, Roadside Mine". The supplemental submittal appears to include portions of that report. The entire report should be included within the supportive exhibits. The findings of that study are referenced to justify the protective pillar technique proposed for use at the Roadside/Cottonwood Mine. (3) The applicant's supplemental submittal observes; "Monitoring of these monuments will begin once mining commences in the area being monitored and will continue beyond the cessation of mining for a period of time necessary to determine the magnitude and other critical aspects of the subsidence." The applicant should include the additional sentence; "Monitoring of the monuments will continue until cessation is approved, in writing, by the Division."