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<br /> <br /> <br /> <br />1 <br />1 <br /> <br />1 <br /> <br /> <br />1 <br /> <br /> <br />t <br /> <br /> <br />1 <br /> <br />Third Party Oversight 7 Water, Waste & Land, Inc, <br />San Luis Mine January 10, 1993 <br />initiate a monitoring program to observe the quantity and rate of tailings consolidation which was <br />occurring as construction of the Raise I Embankment continued (DMG, 7993c). <br />DMG inspected the site on October 1, 1993 (DMG, 1993f), and observed that materials <br />being used for construction of the embankment were not within the original specifications of the <br />Phase II, Raise I impoundment system expansion design repott (SRK, 1993a). As a result of the <br />inspection, BMRI ceased construction on the Raise I Embankment until outstanding issues could <br />be resolved (BMRI, 19938). Placement of the liner system continued. <br />During the site inspection and as initial laboratory permeability test dots were made <br />available, DMG also became concerned with the following: <br />• oversized materials being utilized for the construction of the Raise I Embankment, <br />• gradation of materials being used for the drainage layer/liner cover material, <br />• the lower than specified moisture content of materials being utilized for construction <br />of the low permeability layer, and <br />• drain pipe spacing greater than the specified distances at several locations. <br />Each originally specified material type, its application, and its intent are listed in the Table 2.1. <br />Table 2.1 Construction Material Summery <br />Material Application Intent ISRK, 1993a) <br />Type <br />1 Raise I Embankment Loosely placed sandy gravel material which woul] allow for <br /> enhanced drainage and consolidation of the tailings. <br />2 Drainage blanket/liner Sand material which would protect the VLDPE liner and allow <br /> cover over the VLDPE liner for enhanced drainage of the tailings, thereby reducing the <br /> head on and leakage through the VLDPE liner. <br />3 Low permeability liner Highly compacted sandy silt material which would impede or <br /> underneath the VLDPE restrict leakage from the impoundment. <br /> liner <br />These three materials were the focus of concerns by DMG in the Raise I Expansion. <br />The technical issues associated with the original design intent and actual materials used for <br />Raise I Expansion are outlined in subsequent sections off this report. <br /> <br />