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<br />1 <br />1 <br /> <br />1 <br /> <br /> <br /> <br /> <br />1 <br /> <br />1 <br /> <br /> <br />1 <br /> <br /> <br /> <br />Third Party Oversight 7 Water. Waste & Lend, Inc. <br />Seri Luis Mine June 9, 1994 <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 <br />the impoundment system expansion design report (SRK, 1993a1. As a result of the <br />inspection, BMRI ceased construction on the Raise I Embankment until outstanding issues <br />could be resolved (BMRI, 199381. Placement of the liner system continued. <br />During the site inspection and as initial laboratory permeability test data were made <br />available, DMG also became concerned with the following: <br />^ Oversized materials were being utilized during construction of the Raise I <br />Embankment, <br />^ Materials being used for the drainage layer/liner cover material contained <br />significant percentages of fines, <br />^ The moisture content of materials being utilized for construction of the <br />low-permeability layer was lower than specified, and <br />^ Drain pipe spacing was greater than the specified distances at several locations. <br />Each of the three originally specified material types, its application, and its intent are <br />listed in Table 2.1. These three materials were the focus of concerns by DMG during <br />construction of the Raise I Expansion. The technical issues associated with each material type <br />and the original design intent are outlined in Sections 4, 5, and 6 of this report (Raise I <br />Embankment, Drainage Layer, and Liner System, respectively). <br />TABLE 2.1 <br />CONSTRUCTION MATERIAL SUMMARY <br />Material Application Intent (SRK, 1993a) <br />Type' <br />1 Raise I Embankment Loosely placed sandy gravel material which would 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 layer Highly compacted sandy silt material which would impede or <br /> underneath the VLDPE restrict leakage from the impoundment. <br /> liner <br />Materiel types ere shown on Figure 1. <br /> <br />