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Memo to Tom Schreiner 2 January 25, 2005 <br />Eneineering_Evaluation ofthe Aonlication File No. M-2004-067 <br />time of forfeiture, the DMG would need bond money sufficient to drill, blast, and remove shot rock to <br />establish the benches. The current unit cost for drilling and blasting of this nature is $10.00 per cubic <br />Yazd of intact rock." This unit cost does not include the cost for removal and disposal of the shot rock. <br />This potentially large cost item can be eliminated from the bond to be required if the Applicant <br />commits to operating the quarry such that final reclamation benching for each aspect of the highwalls <br />is maintained from beginning to end of the "ten year" mine plan. This commitment is further <br />necessary to assure that dangerous and costly highwall failures do not occur during the conduct of the <br />operation. <br />4. Waste Rock Storaee <br />The waste rock storage that is proposed under the "ten year" mine plan will cover two minor drainage <br />ways that combine at a fork within the waste rock storage area. Even after the fork, the drainage <br />remains minor and ephemeral. The application proposes diversion of these drainages around the waste <br />rock pile. The drainage diversions and associated culverts and ponds aze outside the scope of this <br />review as they aze being handled by other DMG staff. However, the stability of the waste rock pile is <br />within the scope of this review. It is likely that some of the best soil for reclamation to be found at this <br />site will be located in the drainages. The Applicant should commit to salvaging and stockpiling all <br />usable soi! from the footprint of the waste mck storage azea. In addition, woody vegetation and any <br />azeas of concentrated herbaceous vegetation, as wel- as any other soil or materials that would be <br />deleterious to the stability of the pile, including substantial snow or frozen soil accumulations, must be <br />removed. Preparation of the footprint of the pile should be done in stages as the pile expands. In <br />addition, the Applicant must provide a plan to assure under drainage of the pile through the thalweg of <br />the ephemeral drainages. Given that the pile is to be located neaz the head of these drainages, the dry <br />nature of the location, and the plan to divert flows azound the pile, elaborate underdrains will not be <br />required. A plan that specifies placement of well graded, free draining shot rock, devoid of fines, into <br />the drainages as the pile is built will be sufficient. The required thickness for the wedge of free <br />draining rock to be placed into the drainages should be determined based on the amount of flow that <br />would be anticipated to enter the underdrains during the probable maximum precipitation (PMP) event, <br />assuming that the diversion ditches were non-functioning. Design for the PMP is appropriate because <br />to waste rock pile could be a permanent feature if the bond were to ever go to forfeiture. Ponding of <br />water at the upper end of the pile during the PMP or other large events, with subsequent dissipation of <br />the ponds through the underdrains, is acceptable to the DMG if it can be demonstrated that ponding <br />will not destabilize the pile and that the pond will dissipate within 72 hours. <br />cc: Cazl Mount, DMG (via email) <br />' U.S. Bureau of Mines (1953), Information Circular IC-8925, "Explosives and Blasting Procedures Manual." <br />d AI Amundson, DMG Inactive Mine Program, personal communication. <br />c:~acs\IAANER MACHINEUIy Documen6U1MRR Quarry Eng Review.doc <br />