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~/f% <br />l III III III IIIIIII III <br />• ~ -I~~~= ENGINEERING ~ SURVEYING COMPANY <br />BOX 674 • 443 DODGE DELTA, CO'LOAADO, s1416 303-s74-7593 <br />~~~aaa:raa.uaur a.~-c. .. n ~i•n~ .- ...vim.. ., ~ •~~'. ...a r-t.'.~:~a» <br />RSRO <br />June 12, 1981 <br />State of Colorado <br />Mined Land Reclamation <br />423 Centennial Building <br />1313 Sherman Street <br />Denver, Colorado 80203 <br />ATTN: Jim Pendleton <br />Re: Bear Mine Subsidence Program <br />RECEIVED <br />JUL 13 1981 <br />MINED LAND RECLAMATION-COAL <br />COLO. DEPT. OF NATURAL RESOURCES <br />This letter is to confirm the. details of our telephone converation <br />of June 12, 1981 regarding the above referenced plan. <br />The following points were discussed: <br />1. Length of the subsidence monitoring program for the Bear <br />(`line. <br />You responded with the answer. that subsidence monitoring <br />usually is performed for the length of the bond release <br />period or until the data indicates that no movement is <br />occuriny. I~or the case of the Bear P7ine in which ARCO <br />will be overlying the Bear Mine, this procedure will not. <br />be required. Bear Coal Company wi].1 monitor the subsidence <br />points twice in .L9R1 and once at. the cessation of their <br />operation in the summer of 1982. If any movement is <br />evident from the monitoring program, the Bear Coal Company <br />is to let ARCO know the details of this movement. We <br />are to checl~: with AP--.CO's plan Lur snr.f.ace facilities to <br />determine if Bear's subsidence monitoring monuments will <br />be disturbeci by the surface faci]ities. <br />2. P.eclamation of the highwall above the west portal. <br />You responded with the answer that the highwall does not <br />necessarily have to be backfilled to its original contour.. <br />A critical cross-section will ire analyzed to determine the <br />stabilit~• of the highwall and the bench. The final contour <br />must have a safety tactor of 1. ;. If the stability analysis <br />shoots th;it the hi~]liwall can be hacb:filled to the top with a <br />safety factor of 1. 3, then it must be backfilled that high. <br />