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<br /> <br />1 <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />~) <br />u <br /> <br />1 <br />r <br />1 <br /> <br />Thvd Party Oversight 15 Water, Waste & Land, Inc. <br />San Luis Mine January 10, 1993 <br />A final opinion on the actual in-place permeability of the drainage layer/liner cover <br />material has not been reached as all laboratory data has not been received. Figure 3 contains <br />all laboratory and field data provided to date concerning tailings permeability and laboratory <br />and field permeabilities for the drainage layer/liner cover material. A good correlation exists <br />between dry density and laboratory permeability for the drainage layer/liner cover material, <br />This correlation can be expected from granular materials. Although results obtained with the <br />BAT (field test) system did not provide accurate permeability values (SRK, 1993c), the <br />accompanying dry density values and field notes concerning the compactive effort observed <br />at each test location were valid. <br />Using laboratory permeability test values, the drainage layer/liner cover material at the <br />anticipated placed density is approximately an order of magnitude more permeleble than the <br />mean tailings permeability.? The BAT permeability test results show drainage layer <br />permeabilities slightly lower than the mean tailings permeability. <br />4.4 FINAL CONSTRUCTION AND TESTING <br />The specified frequency for QA tests was outlined in the original 1 12 Fermit (BMRI, <br />1989). An update or change to these specifications was not found in subsegl,lent designs, <br />amendments, or technical submittals (SRK, 1989, 1993a, 1993b, or BMRI, 1993s1. Although <br />density tests appear to have been required for the drainage layer/liner cover material, no <br />density value was specified in the Design Report (SRK, 1993a) or Construction Status Report <br />(SRK, 1993c). WWL's opinion is that density testing of the drainage layer/finer cover material <br />is useful only for correlation with permeability test results. <br />The DMG requested laboratory permeability testing frequency of 1 test per acre on the <br />low permeability material and the drainage layer/liner cover material (DMG, 1993k). The low- <br />permeability material was entirely placed and covered by VLDPE liner by the t me the DMG <br />request vas made. Laboratory tests were also requested by DMG to confirm tf a in-situ BAT <br />permeability test results. Final laboratory results from the drainage layer/liner c over material <br />are required by DMG to verify the preliminary results ISRK, 1993c and 1993d, BMRI, 1993s1. <br />As seen from the Figure 3, material placed with dozers only and not exposed to <br />construction traffic exhibited a dry density of 1 12.6 pounds per cubic foot Ipcfl. Material that <br />had been exposed to both heavy haul traffic and light construction traffic exhibited a dry <br />density of 125.3 pcf. WWL's opinion is that during actual construction a significant portion <br />of the expansion area with flatter slopes (approximately 50 percent of acres 7 through 23, <br /> <br />