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5 ~P 11: UI' ~. Ui U~~nU6 nu ~i:.un n i ntrtA pnvrnun <br />DEPARTMENT OF NATURAL RESOURCES <br />U. f~nn~e Pascor., Earcu live Ovecwr <br />1ttNt':U t,,1NU K{';(:f.;11V1)~'I'ION <br />423 Cenlnnnlal Bull ding. 13t35he n.lan Street <br />Denver, Colo ratio 80203 Tel. (303) 839-3567 <br />October 27, 1')Nl <br />TO: Bob Liddle <br />FROPf: Jim Pendleton <br />~\ t <br />David C. Shelton <br />Director <br />RE: Snowmass North Thompson Creek Mine Ru77,l omen tai Submittal <br />Pursuant to your request, I have reviewed those portions of Snowmass <br />Company's Supplemental permit application submiftal for the North Thompson <br />Creek Mines. I forward the following comments for dour consideration. <br />In general, this submittal rept'esents a significant improvement over past <br />application submittals. lfowever, a Few deficiencies remain to be resolved <br />or clarified. 7 believe it would be beneficial to allow the applicant the <br />opportunitiJ to make minor amendments to Che submittal prior to my drafting <br />findings for your u.sc. <br />(1) Section 4.6.1.5.1 ".inventory of Structures and Renewable Resource <br />Lands....' , <br />The applicant proposes to use limited extraction techniques to <br />prevent subsidence m.aturiol rlnmaye to Counbl Pnad 108, temporary diversion <br />and velocity control structure.: adjacent to C.'ounty Road Z08, the 3G inch <br />truss conveyor system parallel to County Road 108, and portions of North <br />Thompson and Middle Thompson Creeks. 7ls I will discuss here below, this <br />proposal will need additional explanation. <br />(2) Section 4.6.1.5.2 "Descript.iorJ of worst Possible Consequences...." <br />The applicant's engineers make the statement that; "Flowever, subsidence <br />studies have shown that these features (ground surface fractures due to <br />subsidence) usually close up in a short period of Cime with no significant <br />nor lasting effects." While this is a common 7.p held belief within the <br />mining industry, the literature is significantly lacking in actual technical <br />documentation, to my Y.navledye. If the writer is aware of technical docu- <br />mentation existing within the Ziterature or is possession of research <br />supporting this belief, they should include examples or references within the <br />document. <br />(3) Section 4.6.1.5.3 "Subsidence Control Plan" <br />The applicant proposes to prevent material damage to potentially <br />affected structures and renewable rosource lands "...by defining mining <br />limit envelopes eround these features within which full extraction mining <br />will not be conducted without prior approval From the Mined Land Reclamation <br />Board (MLRB)." The applicant does not, however, describe what degree or <br />