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. iiiiuiiiiiiiiuiii <br />DEPARTMENT OF NATURAL RESOURCES 999 <br />David H. Getches, Executive Director <br />MINED LAND RECLAMATION DIVISION <br />DAVID C. SHELTON, Director <br />Richartl D. Lamm <br />Governor <br />DATE: December 5, 1985 <br />T0: Steve Renner ~'`~~ <br />FROM: Jim Pendleton ~ ~"r'"- <br />RE: WOLF CR~E1C'FILL -~SEiVECA II PERMIT REVISION APPLICATION (PERMIT N0. <br />In response to your request, I have reviewed the geotechnical aspects of <br />Peabody Coal's permit revision application. I have one concern, which I <br />believe should be resolved prior to permit revision approval. The underdrains <br />proposed to be constructed beneath the Wolf Creek Fill are being deposited by <br />gravity segregation, using dragline spoil placement. Site inspection has <br />determined that this technique appears to work in the upper and internal <br />segments of the fill, which had been constructed as of last summer. I am <br />concerned, however, that the use of this gravity segregation technique in the <br />portion of the underdrain immediately adjacent to the toe of the fill might <br />compromise the facial stability of the fill. Any reduction in the <br />underdrain's capacity to expel water near the toe of the fill could result in <br />troublesome instability for the final graded facial slope. For this reason, I <br />believe it would be prudent to require the applicant to mechanically segregate <br />coarse material for placement in that portion of the underdrain to be <br />constructed within 100 feet of the final facial slope. I reconmend that the <br />Division require this final segment of the underdrain be constructed with <br />durable rock prior to the dragline placement of spoil in this final segment of <br />the fill. I do not believe that this requirement will represent a significant <br />hardship for the permittee, and it should help assure a maintenance-free <br />facial slope for the Wolf Creek Spoil Fill. <br />cc: Mike Savage <br />/ph <br />Doc. No. 5512 <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567 <br />