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I <br />Third Party Oversight 18 Water, Westa & Land, Inc. <br />' Sen Luis Mine June 9, 1994 <br />' WWL was informed that the following corrective actions were being considered by <br />BMRI: <br />^ Remove and replace out-of-specification material with in-specification material. <br />' ^ Import and blend in-specification material with the out-of-specification material. <br />' ^ Place in-specification material to cover the out-of-specification material (to a <br />sufficient depth) to provide for acceptable drainage around these aneas. <br />' WWL considered each of these actions to be acceptable as they retained the original <br />intent of the design, but preferred the placement of additional material on top of the <br />out-of-specification material to avoid possible disturbance of the synthetic liner. WWL's <br />opinion is that this area was small in comparison to the overall expansion and would not <br /> <br /> <br />1 <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br /> <br />significantly affect the overall performance of the drainage blanket/liner cover. <br />5.3 PERMEABILITIES <br />The Design Report ISRK, 1993a) did not specify a permeability for the drainage <br />layer/liner cover material; however, results of field C.A permeability tests conducted with the <br />BAT in-situ permeability testing system indicated that permeability of the pldced Type 2 <br />material ranged from 1.6 x 10-0 cm/sec to 3.6 x 10'° cm/sec (SRK, 1993c1. Results from four <br />of the BAT tests are shown on Figure 3 (with corresponding density testsl. These <br />permeabilities appear to be significantly lower than would be expected from materials with <br />the Type 2 gradation specification and the compactive effort apparently applied (based on <br />density test resultsl. As stated in the Construction Status Report (SRK, 1993c1, the BAT <br />system is well suited for testing clayey type soils possessing permeabilities less than 1 x 10° <br />cm/sec; however, the BAT system was not well suited for material with permeabilities greater <br />than 1 x104 cm/sec. The BAT permeability values were slightly lower than the mean tailings <br />permeability (shown in Table 5.1l. Table 5.1 summarizes available laboratory and field <br />permeability test results from the tailings. <br />TABLE 5.1 <br />SUMMARY OF MEASURED TAILINGS PERMEABILITY VALUES <br />Information Source High (cm/sec) Low (cm/sec) Average(cm/sec) <br />Permit Application Amendment 2.5 x 10"5 5.0 x 10~° 1.8 x 10'fi <br />ISRK, 19891 <br />Design Report, Piezocone Data 7.2 x 10"° 4.2 x 10'' 2.4 x 10'° <br />ISRK, 1993a1 <br />Construction Status Report, CPT' Data 1.9 x 10'5 5.9 x 10"B 4.0 x 10'° <br />ISRK, 1993c1 <br />~ CPT -Cone Penetrometer Test <br /> <br />