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7 •. I h ~ l . ~~ i t n ~~( A~ n ~ u u pia uii l~ i ,.~~...,..•. •.~ <br />urrnnlMrNl nr rvnmm~l nrsnulu:rs <br />n Mnulr ".r,rur I . udwc 11u ~•nm <br />11 I N 1? I 1 1.,~ IV I I li I'a :I .+11111' I'll) N <br />A23 Cenlen nlal Dullding, 1313 Sherman Street <br />Drn ver. Colo mdn 80203 Tel 1303) 839-3567 <br />David L. Shelton <br />Director <br />14arch 12, LrRi <br />TO: Tom Gillis, Reclamation Specialist ~ <br />FROM: Ji ur Pendleton, Senior Geologist ~ \ <br />/~ <br />RE: Review of the Subsidence Aspec~f Color do wes tmoreland, Ine.'s <br />Orchard L'a11ey Mine Plan <br />Pursuant to your request, I have completed a review of the amended permanent <br />program permit application submitted by Colorado Westmoreland, Znc. for the <br />Orchard Valley Coal Mine. This memorandum presents comments for your <br />consideration regarding the subsidence aspect of that permit application. <br />Colorado Westmoreland, .Inc. presents a subsidence projection based upon: <br />(1) British 12ational Coal Board empirically drived equations for maximum <br />predicted subsidence and tensile surface strain, and (2) empirical observations <br />done by CWI above its existing workings. The amended application proposes <br />a quarter section corner subsidence n+nnument monitoring plan overlying the <br />proposed Orchard Valley mine i,rnrl:inys. With a few revisions the application, <br />in its amended form, will conform with the requirements of the regulations <br />of the Colorado permanent regulatory program [Rule 2.05.6(6)]: <br />1. On page G8 of the amended application, under Phase II of the proposed <br />monitoring program, C'!JZ proposes semi-annual survey of its monitoring <br />monuments. Rule 2.OS.G(G)(c)(i) requires quarterly surveying with semi-annual <br />reporting of the survey results to CMI•RD. This same section of the application <br />also states that the monitoring will cease when it is determined that no <br />further subsidence will occur. Monitoring must continue until concurrence <br />on its cessation is received from the CMLRD. <br />2. In a letter from Donald A. Crane, Director of Region V of the Office <br />of Surface Mining, to Daniel J. Snyder, III, President of CWI, dated September <br />28, 1979, the OSM requested that CWI establish additional monitoring points <br />above its unrlcryround workings. "The proposed monitoring stations are not <br />located close enough to monitor subsidence in the initial panels on lease <br />C-27432. Yau are therefore requested to consider estabtishiny a minimum of <br />Lwn ::urve~l trnnr:ects, which c•rczss th.~• fifth and sixth cast panels." <br />It is CwI's contention that "...the threat of adverse impacts from the <br />effects of subsidence on the ground surface, surface water, and ground water..." <br />will be minute. (page 70) "A1Nlouyh C'p~I is convinced that no adverse effects <br />related Lo subsidence will be experi.::nced, the previously mentioned subsidence <br />monitoring program will ren><~in in clfrr-t at the Orchard Valley Mine." (page 71) <br />(con t' d) <br />4 <br />i l l ~ i. L <br />