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iiiiiiiiiiiuiuiii ~ <br />DIVISION OF MINERALS AND GEOLOGY <br />Deparimenl of tJamral Resources <br />1 31 3 Sherman SL, Raom 215 <br />Dcnve~, Colorado 80203 <br />Phone. 13071 abn-3567 <br />r.ax:~la31a32-aeon <br />STATE ~ COLORADO <br />RECEIVED <br />February 20, 1998 <br />Division of Minerals & Geology <br />Mr. Alan Cox <br />Manager -Environmental Affairs <br />Homestake Mining Company <br />650 California Street <br />San Francisco, California 94108 <br />DENIER OFFICE <br />PUBLIC FILE COPY <br />FILE: /j'I-77-2 ~S <br />SITE: <br />7 - 07 <br />RE: Bulldog Mine, File M-77-215, Technical Revision No. 7 Adequacy Review <br />Dear Mr. Cox: <br />~~ <br />DEPARTMEI~IT OF <br />NATURAL <br />~souRCEs <br />Roy Romer <br />Gus e~~or <br />lames 5 Lorhhead <br />E.ec ulne Direcmr <br />nvchael d Lune <br />Dn isiun Di~e<ior <br />The Division has completed the adequacy review of Homestake Mining Company's (HMC) application for <br />Technical Revision No. 7 to Permit No. M-77-215 which addresses sealing the 9360 level adit and <br />implementing a monitoring plan to verify the seal's effectiveness at hydraulically plugging that adit. <br />The following concerns were identified during the review. Please address these concerns as soon as possible, <br />so the decision due date of March 13, 1998 can be met. <br />HMC must provide, for Division approval, all specifications on the concrete chosen for plugging the <br />adit prior to construction of the seal, e.g. type of cement, gradation of aggregate, etc. <br />2. 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 inoculate the adit, behind the plug, with a tracer that can be used to identify groundwater that <br />may seep from the mine pool behind the plug. The monitoring plan will need to include provisions for <br />testing for the tracer substance, including a proposal for tracer sampling locations in Windy Gulch. <br />4. The last inspection reporc for the Bulldog Mine indicated that caving, in the vicinity of daylight curve, <br />had left the adit roof approximately 30 feet high, as far as could be seen in both directions. Please <br />verify how far toward the 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 adit, 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 such instability problems. <br />If 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 Protec on Specialist <br />cc: Allen Sorenson <br />