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48 Groundwater <br />The valley fill monitoring well network was designed to collect groundwater level and <br />water quality data in the stream channels. Wells were installed upstream of potential <br />mine operations in Straight and Collom gulches (MS -04 -01 and MC- 04 -01, respectively). <br />Downstream wells were located to evaluate predevelopment conditions and potential <br />changes in water quality after the start of mine operations in Little Collom Gulch <br />(MLC- 04 -01), lower Collom Gulch (MC- 04 -02), and lower Straight Gulch (MS- 04 -02). <br />Data downgradient of the Collom Mine in Jubb Creek was provided by preexisting wells <br />MJ- 95 -01, MJ- 95 -02, and MJ- 95 -03. The location of Little Collom Gulch valley fill well <br />MLC -04 -01 was based on the proposed use of Little Collom Gulch as a spoils stockpile <br />under the Option 1 mine plan. <br />The new valley fill monitoring wells were installed in 4 -inch diameter holes drilled using a <br />wireline coring rig with air /foam or water as the circulation fluid. The wells were <br />completed with 2 -inch diameter Schedule 40 PVC casing and screen. Wells were <br />developed by bailing and with a submersible pump in accordance with the WMC SAP <br />(Appendix 1.13). Details of the well completions are provided in Table 5.3. Well <br />completion logs are provided in Appendix S.B. <br />5.2.4 Collom area piezometers <br />Fifteen standpipe piezometers and three vibrating wire piezometers (VWP) were <br />installed in November and December 2004 to evaluate the distribution of water levels <br />C across the proposed Collom Mine as a function of location, geologic unit, and time. The <br />piezometers were completed in discrete units of the Williams Fork Formation, including <br />the F sandstone, F/G coal, Fab coal, H coal, H sandstone, and I sandstone. The <br />locations of the bedrock'piezometers are shown on Figure 5.7. All bedrock piezometers <br />were installed in 6 -inch diameter holes drilled using standard rotary methods with <br />air /foam or water as the circulation fluid. The piezometers were completed with <br />1.25 -inch diameter Schedule 40 PVC casing and screen. Standpipe piezometers were <br />developed with a surge block in accordance with the WMC SAP (Appendix 1.13). <br />Piezometer completion details are provided in Table 5.4, and completion diagrams are <br />provided in Appendix 5.C. <br />A VWP differs from a standpipe or screened piezometer in its use of an electrical <br />transducer that converts pore pressure into an electrical signal. Each location consists <br />of a single 5.625 -inch borehole with three vibrating wire piezometers installed to monitor <br />water pressures in specific units of the Williams Fork Formation. Installation and <br />completion details for the VWPs are described in Section 5.2.5. <br />2572 -R2 <br />Colowyo Coal Company <br />Water Management Consultants <br />