2007-11-15_PERMIT FILE - M2007044

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STATE OF COLORADO DIVIS!(7N (3F RECLAh1ATi0l+#, M!NlNG AtJD SAFETY De{~artment ~t hvatural Resources i 313 Shc:nnan St., Raum1 i 5 C O L O R A D O ntvisio~r of [7ZfiVE'r, CoEarac#o ~02a3 RECLAMATION Phone.: 13033 866-3567 MINING i=AX: C3D3i 832-81(76 SAFETY .DATE: l~lovember 14, 2007 fti!! Ritter„r. C.lciverner Nanis D. Sherman TO: Russ Means ! ; Executive Oircxtar f' ! ,/~ RonalcS 11'. Cottony FROM: Allen. Sorenson ~ ? ~. ` „`~ pivision Direttar Natural 12esource Trustee RE: Cost Estimate for Water Impounding Concrete Bulkheads, Energy Fuels Resources Corporation, Whirlwind Mir:e, File No. M-2447-444 The Division of Reclamation, Mining, and Safety (DBMS) engineering staff have completed a review of the underground water impounding bulkhead information provided in the Whirlwind Mine permit application as supplemented by the Bulkhead Locations plan provided by Lewicki and Associates and dated October 27, 2007. The Applicant proposes a main bulkhead 148 feet in elevation below the decline portal where the decline dimensions are 12' x 9' and there is approximately 470 feet of ground cover. A secondary bulkhead is proposed for a location 134 feet in elevation below the decline portal. Lewicki and Associates has recently communicated to the DR.MS that the upper bulkhead is no longer deemed necessary since the Bureau of .Land Management is requiring the decline portal to be backfilled However, the .DBMS will require that an upper water impound.i.n.g bulkhead be bonded as a contingency as discussed in the memo dated November 6, 2007 (Allen Sorenson to Russ Means). The same memo describes the need to bond for a contingency bulkhead in the Packrat Mine workings. For the purpose of estimating a cost, .DBMS will assume conservatively that the Packrat Mine bulkhead would be installed 26$ feet in elevation below th.e decline portal where the adit dimensions are i 2' x 9' and at a location where there is sufficient ground cover to prevent hydrofracing of the .formation around the bulkhead It is indicated in the application that precise location selection and detailed designs for the bulkheads is premature at this time; D:RMS concurs. It is necessary to preliminarily consider design basis for the bulkheads in order to estimate costs, and this memo provides an analysis of the type of bulkheads that will be necessary in order to develop costing information and estimate the amount of bulkhead bond to be required. Einarsan.and Abel (.1990) present astep-by-step procedure for design. of underground water irrtpour~tding bulkl-~eads. Conservatism in design f~f the bulkheads is necessary because of the safety and etviran:n~er#.tal irrtplications of a bu.l.khead faiurtW, the 1€~n.g life required for the bul.kheacts, ancl. the ultirrlatc i.#~accessi:bility of the bulkheads. 'I`he Ameri.ean Concrete ln.stitute's "Bui.ld.ing f;ode Regiren~en.t.s for R.cinl'arcecl. Concrete (AC"I.318W$9)" is usetii be~aus~. the bulkheadG are analogous to rt;:ir~forced steep-burn concrete structures and. because of the inherent cv~.iservatisr~~ of the code. 'i~he analysis presented in this memo generally follows the Einarson and Abel template. "l,he maximum hydraulic head and pressure at the proposed main bulkhead are as follows: CI =1.4$ feet II y~ _. 148 X (~2.4 .._ Ei4 ~sr ~.44i~ g_ __._ -- __~__-_____~_..____~._.._.___~.._------------- - Qlfics~ irf C~ft"ict~ of ?C.ti~,+e and Inactive MinfYc iv~linecf I..areti Rfrrlarr«s±ic:n Denver Grand #unclion C3uran~n