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-, • <br />• ~II'I~~II~II~~~~ ~II <br />sss <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Deparlmenl w Nawral Re>ourccs <br />I3 U Shcrm.m 51.. Ruum ? I S <br />Denver, Colorado 8(L'0 f <br />Phone: 13071 866- 4567 <br />FAX: 13031 832-81 U(r <br />DATE: January 24, 1996 <br />TO: Berhan Keffelew <br />FROM: Allen Sorenson ~ = <br />RE: Procedures aad~ Materials <br />Project, Cripple Creek sad <br />No. M-SO-244 <br />I~~~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />Roy Romer <br />Go~ernrn <br />lames 5 Lo~hhead <br />EsecuLVe DueClor <br />Mic hacl B. Long <br />D rvmm~ Dvcrlrn <br />for 1996 Construction, Cresson <br />Victor Gold Miniag Compaay, Permit <br />The operator has proposed a change in the approved specification for <br />thickness of the Drain Cover Fill from 3 feet to 2 feet. The <br />operator has supported this proposal by stipulating pressure <br />limitations for equipment used to place the Drain Cover Fill, and by <br />stipulating uphill placement of Drain Cover Fill on steep slopes and <br />disallowing abrupt turns by equipment used to place Drain Cover <br />Fill. It is my opinion that a 2 foot thick layer of Drain Cover <br />Fill is insufficient to protect the soil liner in the ore storage <br />area from freeze-thaw cycling. Exposure to only a few freeze-thaw <br />cycles could increase the permeability of the soil liner, thus <br />reducing its leak attenuation properties. Also, if any non- <br />specification maneuvering of equipment were to occur on a 2 foot <br />Drain Cover Fill layer, particularly pivoting of a bull dozer, <br />damage to the primary liner could be severe. This being the case, <br />by approving a reduction in Drain Cover Fill thickness, the Division <br />would be eliminating a degree of conservatism directly related to <br />environmental protection that is currently a binding component of <br />the existing permit. <br />The operator has proposed a change in the approved specification for <br />thickness of the Low Volume Solution Collection System Fill (LVSCF) <br />from 3 feet to 2 feet, supporting the proposal with the same <br />equipment pressure and placement methodology limitations as for the <br />drain cover fill. Once again, any non-specification maneuvering of <br />equipment were to occur on a 2 foot LVSCF layer, particularly <br />pivoting of a bull dozer, damage to the secondary liner could be <br />severe. This being the case, by approving a reduction in LVSCF <br />thickness, the Division would be eliminating a degree of <br />conservatism directly related to environmental protection that is <br />currently a binding component of the existing permit. Also, the <br />operator's proposal does not address the ability of the Low Volume <br />Solution Collection System to maintain a 2 foot thick LVSCF matrix <br />in a dewatered state. If any of the 2 foot thick layer were to <br />