2006-06-05_REVISION - M1987028 - Laserfiche WebLink

Home Browse Search

STATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY Department d Natural Resources t 3 U Sherman St., Room 2 r 5 C O L D RA D O Dmsx, Coloodo &1203 D l v t s t o to o r Nsone: 1)03) 8647567 MINERAL S rnx: t3on e32d106 & GEOLOGY IIC UN.,TION•M~MiNG tuR n1C ~INCI DA"f E: June I, 2006 BiO~^^* c:wl.~« Ruwll Gagr TO: Erica Crosby r,K,,,,wa,R,o, RmaW W. GYlanr PROM: Allen Sorenson onna,ar~m, KXUnI Re»urte rrufYe Rh.': Georeclurical AdequurV Rev/ew, C'aloradu ,lfarhle, / / G, !.illy ,!!lets, Conyers/on;Ippliculion C)Y-01, Permil:Vo. ,11-1987-028 The Division of Minerals and Geology (DMGI engineering staffhavc reviewed the g~rotcchnical aspcr.ts of the (bnversion CN-01 application liar Lilly Mines and have determined that the fulluw~ing issues remain to be resolved prior to approval of the application. I. It is stated in Exhibit D to the application that the secondary jointing pattern in the marble formation strikes N90°E and dips 7fi"E. Since this orientation is gconJCtrically impossible, and since it is stated in the Geotc~chnical Stability Exhibit that the sccondaryjoint set dips 7(i'N, DMG believes the discrepancy to be a typographical error, but this must be clurilicd by the Operator. 2. It is stated in Exhibit D to the application that surface drainage of snow melt, rain stone events, and seasonal surface water flow will be directed to the south from collection above the west highwall and eventually into the southern end of the mining area, where it is directed in to the lower pit area. It is further stated that surface water does not collect in the lower pit area but quickly percolates into the well-fractured carbonate bedrock. Finally it is stated that collcctiun and diversion of all surface water (lows into the marbly pit Irom fornler underground metal mining operations located above the marble mining lone will help to mitigate any putcntial for low pl{ water that might be sourced from old metal mint workings. D\~iG has the following concerns. a. ('ollcction and diversion of stone water and snow melt around the quarry is a good management practice. However, as stated in the DMG's April 25, 2006 adequacy letter. muting water from up gradient of this quarry operation around the quarry may hcucr be discharged into the natural drainage rather than into the lower pit arcs. I f one of the Operator's considerations for routing the water info the lou•cr pit area is to provide passive treatment of putcntial acid ruck drainage liom up gradient historic mines, the discussion provided in item 2.b. below should be carefully considered. If the Operator persists with the plan to route upland water to the lower pit, the following issues must be addressed. i) I'he lower pit area must be capable of fully containing runoff from the 10- ycar24-hour stornl event and must safely pass the 100-year%24-hour storm into the natural drainage. In accordance with requirements of the Office of vmcr or OtLcc of Colorado Mlnld Land Reclamatial Acvve and Iructive Mines Caological Surer