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description of the material suggests that the top of bedrock behaves as an aquitard (low <br />permeable barrier) for the overlying alluvial aquifer. <br />Table 1 <br />Summary of May 2006 Bore Hole Data <br />2.3 Alluvial Aquifer Characterization <br />The exploration borings and other available information were used to construct a conceptual <br />hydrogeologic model of the site prior to the current mining operation. For the purpose of <br />characterizing the hydrogeologic conditions for the site, the subsurface materials can be <br />subdivided into three units: a silty /sandy clay overburden, permeable unconsolidated sand and <br />gravel deposits, and low permeability bedrock. Bedrock is covered by alluvium throughout the <br />property. In general, the thickness of the alluvium ranges from approximately 30 to 35 feet <br />across the project site. Local fine- grained clay or silty clay zones occur as lenses or <br />discontinuous beds within the alluvium, but none of the layers appear to be laterally continuous <br />(Deere and Ault 2007). Therefore, the subsurface information suggests that the alluvium can <br />conceptually be considered one aquifer. <br />Bore log data collected at the time of drilling was used to estimate alluvial aquifer characteristics <br />such as groundwater elevations and saturated thickness (Table 1). Since Parcels 1 and 2 of the <br />Evans #2 Pit (see Figure 1) were being mined and dewatered at the time of the May 2006 <br />"blue ea, ' 1 h Page 3 of 11 <br />SOLUTIONS <br />Ground <br />Groundwater <br />Bedrock <br />Saturated <br />Surface <br />Elevation(') <br />Elevation <br />Thickness <br />Bore Hole <br />Elevation <br />(feet amsl) <br />(feet amsl) <br />(feet amsl) <br />(feet) <br />THM -1 <br />4536.7 <br />4517 <br />4499 <br />18 <br />THM -2 <br />4538.8 <br />4516 <br />4501 <br />15 <br />THM -5 <br />4528.3 <br />4514 <br />4493 <br />21 <br />THM -8(21 <br />4529.0 <br />4512 <br />4499 <br />13 <br />THM -9 <br />4527.8 <br />4517 <br />4494 <br />23 <br />THM -12 <br />4523.6 <br />--- <br />4488 <br />- - - <br />THM -14 <br />4525.8 <br />4517 <br />4492 <br />25 <br />T14M -16 <br />4521.5 <br />4514 <br />4487 <br />27 <br />(l) Groundwater elevation encountered during bore hole drilling <br />(2) Groundwater elevation apparently influenced by 2006 Evans #2 Pit <br />dewatering operation <br />(3) --- data not available <br />(4) amsl = above mean sea level <br />2.3 Alluvial Aquifer Characterization <br />The exploration borings and other available information were used to construct a conceptual <br />hydrogeologic model of the site prior to the current mining operation. For the purpose of <br />characterizing the hydrogeologic conditions for the site, the subsurface materials can be <br />subdivided into three units: a silty /sandy clay overburden, permeable unconsolidated sand and <br />gravel deposits, and low permeability bedrock. Bedrock is covered by alluvium throughout the <br />property. In general, the thickness of the alluvium ranges from approximately 30 to 35 feet <br />across the project site. Local fine- grained clay or silty clay zones occur as lenses or <br />discontinuous beds within the alluvium, but none of the layers appear to be laterally continuous <br />(Deere and Ault 2007). Therefore, the subsurface information suggests that the alluvium can <br />conceptually be considered one aquifer. <br />Bore log data collected at the time of drilling was used to estimate alluvial aquifer characteristics <br />such as groundwater elevations and saturated thickness (Table 1). Since Parcels 1 and 2 of the <br />Evans #2 Pit (see Figure 1) were being mined and dewatered at the time of the May 2006 <br />"blue ea, ' 1 h Page 3 of 11 <br />SOLUTIONS <br />