Laserfiche WebLink
62 Groundwater <br />In general, groundwater elevations in the bedrock wells did not vary more than 10 ft after <br />the initial post - development equilibration period. The exceptions were: <br />• PC- 04 -25FG (screened in the Fab seam), which has dropped 16 ft since <br />it was installed; <br />MWC -04 -29FS and PC -04 -29FS, both of which have dropped 12 ft; <br />MWC- 04 -29H, which has dropped 17 ft; <br />PC -04 -081, which has risen 17 ft; and <br />PC -04 -281, has been dry since shortly after it was installed. <br />Given that most of the wells were installed relatively recently in a complex hydrogeologic <br />environment, the causes.and significance of these water level changes cannot be easily <br />determined. Water levels in these wells will be evaluated at a later date to determine <br />whether the observed changes are attributable to installation of the wells or reflect some <br />normal component of hydraulic behavior. <br />The absence of water in upgradient well PC -04 -281 indicates that the I sandstone is not <br />saturated at this location. The observation that the other two I sandstone piezometers <br />(81 and 381) both display a rising water level, with increases of 17 and 5 ft, respectively, <br />( may be indicative of a very low permeability unit with limited recharge. <br />As shown on Figures 5.11 through 5.14, groundwater flows down dip towards the north. <br />Relatively steep gradients occur on the south portion of the mine footprint (approximately 0.3 <br />in the F sandstone and 0.18 in the F/G sequence). The gradients flatten considerably in the <br />central and southern parts of the proposed Collom Mine to approximately 0.04 in the F, H, <br />and I sandstones and F/G sequence. <br />Valley fill levels <br />Valley fill groundwater elevations appear to be controlled by a combination of the nearby <br />streams and seasonal variations in flux through the valley fill. For the period of record <br />(August 2004 through May 2005), alluvial water levels generally increased. <br />Hydrographs for the alluvial wells are provided in Appendix 5.J. <br />5.2.11 Groundwater quality monitoring <br />Water quality samples were collected for baseline monitoring of the pre- mining <br />environment. The data will be used to help evaluate the potential hydrologic impacts <br />that may occur as a result of result of coal mining. Until development of the mine starts, <br />the purpose of the groundwater quality monitoring programs is to collect representative <br />data that reflect both the temporal and spatial variations across the site. Currently, the <br />baseline groundwater sampling program has met the sampling frequency and parameter <br />requirements established in the Work Plan, which was reviewed and approved by the <br />CDMG (Section 1.1). <br />2572 -R2 Colowyo Coal Company <br />Water Management Consultants <br />