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5TATE OF COLORADO <br /> DIVISION OF MINERALS AND GEOLOGY <br /> Department of Natural Resources a�°V <br /> ' o <br /> 1313 Sherman St., Room 215 l t G r <br /> Denver,CO 80203 \* <br /> Phone:(303.)866-3567 *JR76� <br /> FAX (303)832-8106 <br /> Roy Romer <br /> Governor <br /> DATE: October 13, 1993 <br /> Michael B Long <br /> Division Director <br /> TO: Tony Waldron <br /> FROM: Jim Pendleton <br /> RE: Interaction d Refuse Pile & Drainage Ditch <br /> Coal Basin Mines (Permit No: C-81-017) <br /> In response to Larry Routten' s request of August 23, 1993, I <br /> visited the Coal Basin mine site on my way to the Craig Board <br /> Meeting on the afternoon of Tuesday, September 21st. I regret that <br /> my schedule did not allow me to visit the mine earlier or to <br /> prepare this final draft in a more timely fashion. <br /> For efficiency I will directly address the concern addressed in Bob <br /> Hagen' s comments in reply to your TDN 93-020-190-TV4 response. <br /> Briefly, the Albuquerque Field Office believes that the ditch which <br /> crosses the toe of the old refuse pile immediately above Coal Creek <br /> is contributing to the instability of the toe of the refuse pile. <br /> The lower portion of the pile and the ditch are pre-law, but the <br /> ditch was permitted under the permanent program permit. <br /> The relatively small drainage ditch crosses the lower portion of <br /> the old refuse pile approximately 20 feet upslope from Coal Creek. <br /> As was common practice in the 19601-s when it was constructed, the <br /> Operator installed wooden cribbing on the upper slope of the toe of <br /> the 'refuse above the ditch. Cribbing is comprised of "deadman" <br /> timbers sunk approximately five feet into the refuse, with lateral <br /> timbers connecting the "deadman" . This forms a lattice-like <br /> boxwork which retains the refuse. Briefly, the cribbing functions <br /> like a chinese finger puzzle. As the weight of the increasing <br /> refuse pile causes the refuse to consolidate and settle, increasing <br /> frictional grip is applied to the ttdeadman" . The "basket" settles <br /> and strengthens. The system is intended to be flexible and to move <br /> as it matures . Obviously, wooden timbers, even if Wolman Salt <br /> impregnated, will not survive indefinitely. However, as the <br /> timbers degrade and eventually disintegrate the pile has achieved <br />