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of coo DEPARTMENT OF NATURAL RESOURCES <br />~~ R <br />F.e YO D. Monte Pascoe. Executive Director <br />~n~;. ~ MINED LAND RECLAMATION DI <br />• ,,, ,,.; • DAVID C. SNELTON, Director <br />} X876 F <br />Ric nartl D Lamm <br />Governor <br />July 26, 1983 <br />T0: Mike Savage 1~c-~~- <br />FROM: Jim Pendleton <br />RE: Review of Bo~}rcj Co3- s Swell Factor Calculations and <br />Correspondirfg-Permit Revisions <br />Pursuant to your request, I have reviewed the swell factor determination <br />and corresponding permit revisions submitted by Walden Coal Company for <br />the Bourg Strip Pit. These calculations, prepared by Robillard and <br />Associates, Inc., consultant to the operator, present the results of a <br />stereophotogrammetrlc analysts. The analysis determined that 1,160,000 <br />loose cubic yards of overburden and topsoil have been produced from a <br />1,020,000 bank cubic yard excavation. Production records demonstrate <br />that approximately 141,000 bank cubic yards of coal were included within <br />the excavated material. <br />The operator's subsequent calculations demonstrate that an overall <br />intrinsic swell factor of 32°~ has been experienced to date. My <br />calculations determinated that this represents an overall bulking factor <br />of 1.137. The applicant's original assumption of an intrinsic overburden <br />swell factor of 23% would have resulted 1n a correspondiny overall <br />bulking factor of 1.06. Therefore, the operator's backfilled volume <br />currently exceeds projections by approximately 80,000 cubic yards. If we <br />assume the operation to be approximately 2/5 complete, the life-of-mine <br />mtyht result in approximately 200,000 cubic yards of swollen backfill in <br />excess of the amount oriyinally predicted. <br />The amended permit application states that the operator believes the <br />implications of this error to be insignificant. In my opinion, the <br />information submitted is inadequate to ,justify that statement. I <br />recommend that you require the operator to develop a worst-case <br />alternative backfilling and gradiny plan, in order to demonstrate that <br />the additional p.ro,jected swollen backf111ed volume can be accommodated <br />without creating an environmental or slope stability problem. <br />/mt <br />cc: Brian Munson <br />Dot. No. 4543 <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567 <br />-III IIIIIIIIIIIII III <br />999 <br />