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OS/lIS/98 TU8 1d:2S FAI ~1S 897 5019 <br />- ~ • <br />DIVISION OF MINERALS AND GEOLOGY <br />Uewnment of Natural Rcaources <br />1313 Shaman 51., Room 215 <br />Denver, Colorado e02D3 <br />Plwne: 13U31 NE.5-3567 <br />fn%: IlDll R32-PIU6 <br />February 20, 1998 <br />Mr. Alan Cox <br />Manager • Envirorvnerttal Affairs <br />Homestake Mining Company <br />650 California Street <br />San Francisco, California 94108 <br />901lESTAIOr MINING ®002 <br />• <br />STATE OF COLORADO <br />E.~ ~;` lCeJ <br />~ys~~ v~Wrr <br />RE: Bulldog Mme, Fde M•77.215, Technical Revision No. 7 Adequacy Rsview <br />Dear Mr. Cox: <br />Roy Raner <br />Governor <br />)ernes s. l«nhexl <br />Eaxulive Dinctw <br />Michael B. Eorr~ <br />Di.i.io,. Dinmr <br />The Division has completed the adequacy review of Homestake Mining Company's IHMC) application far <br />Technical Revision No. 7 to Permit No. M-77-215 which addresses sealing the 9360 level edit and <br />implementing a monitoring plan to verify the seal's effectiveness at hydraulically plugging that edit. <br />The folbwing cor-cems were identified during the review. Please address these concerns as soon as possible. <br />so the decision due date of March 13, 1998 cart be met. <br />HMC must provide, for Division approval, all specifications on the concrete chosen for plugging the <br />edit prior to construction of the seal, e.g. type of cement, gradation of aggregate, etc. <br />Z. Please provide all specifications on the water drain pipe which will be installed in the plug, e.g, type <br />of steel, weight per foot, etc. <br />3. The plan to monitor for seeps is inadequate and would probably be inconclusive. Please propose a <br />plan to inota>rate the edit, behind the plug, with a tracer that can be wed to identify groundwater that <br />may seep from the mine pod behind the plug. The monitoring plan will need io include provisions for <br />testing for tfte tracer substance, including a proposal for tracer sampling locations in Windy Gulch. <br />4. The last inspection report for the Bulldog Mies indicated that roving, in the vicinity of daylight curve, <br />had left the edit roof approximately 30 feet high, as far as could be seen in both directions. Please <br />verify how tar towaM tl+e portal, this high roof extends. indicate the amount of cover between the <br />outermost point of this Caved area, and the ground surface. Provide a demonstration that possible <br />saturation of the ground in the vicinity of the edit, at maximum proposed mine pool, will not create <br />a stability problem that could manifest itself in surface slumps or subsidence features. Also that <br />repeated saturation and draining of this area will not contribute to wch instability problems. <br />It you have questions or need additional information, please contact me at our Durango Field Office, 484 <br />Turner Drive, Building F, Room 101, Durango, Colorado 81301, phone no. (9701 247-5062. <br />Sincerely, <br />~~ <br />Steve S. Shuey <br />Environmental Prote on Specialist <br />cc: Allen Sorenson <br />