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H'r'DF•i ik I NET I C' I NC. <br />• <br />12975 W. 24th Pl. <br />Gulden, ~Applewood) Colorado, 80401 <br />(303) 237-8865 <br />August 1R, 1992 <br />Dr. .lames A. Pendleton <br />Technical and Scientific Coordinator <br />Colorado Mined Land Reclamation Division <br />1313 Sherman Street, Room 215 <br />Denver, Colorado 89203 <br />9._.~__•__ ~ <br />• <br />RE: Review of "Modifications to Existing Ground Water <br />Monitoring System, Battle Mountain Gold Mine, August, 1992." <br />Dear Mr. Pendleton: <br />As we discussed by phone, we have some concerns with the <br />recently released study concerning "Modifications to the Existing <br />Ground Water Monitoring System" at Battle Mountains San Luis Mine. <br />The drilling and well testing achieved a number of the goals <br />initially established, but some unanswered questions remain. <br />Additional information on the geology of the site was collected, <br />the direction of ground water flow was established as the gradient <br />was defined, and information on the hydraulic conductiv~.ty of the <br />material in the upper portion of the aquifer was developed. This <br />has all been accomplished in a professional and well documented <br />manner. However, specific information on the porosity, or more <br />importantly the effective porosity, of the aquifer maternal was not <br />collected. Additionally, the aquifer tests were not conducted for <br />a long enough duration to allow drawdown to occur in the other test <br />wells, and no monitor wells were installed. Consequently, no <br />values for the storage coefficient of the aquifet can be <br />calculated. The report suggests this deficiency was caused by the <br />time restraints imposed by MLRB, though we anticipate such <br />restraints could have been resolved if needed to collects accurate <br />data. <br />The report utilizes the data collected to project ground water <br />flow velocities. The assumption is made that the effective <br />porosity is 25$. Since porosity is inversely proportional to <br />groundwater flow velocity, an accurate value for this parameter is <br />important. The 25$ value may be appropriate, but there is no <br />supporting data to confirm this to be true. <br />F.92 <br />Grvu::d Ll'ater Hydruing~~ Eneineerin_ Gml~7ec Genphv5~C5 C;int~;d:ni~;J C„n~~.ulcanr. <br />