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Mountain Coa! Company 1997 Annual Hydrology Report West E!k Mine <br />• Groundwater Impacts <br />The groundwater monitoring system at the West Elk Mine is shown on Map 2 and summarized <br />in Table 4. Table 5 shows the completion information for the thirty-two wells [hat aze currently <br />monitored at the West Elk Mine by the formation in which they were completed. These <br />formations include: the alluvium and colluvium (unconsolidated materials), the Barren Member <br />of the Mesa Verde, the F-Seam, the E-Seam, the B-Seam and the Rollins Sandstone. <br />Graphical representations of the historic water levels observed at these monitoring wells can be <br />found in Appendix F. Water level and quality data obtained in WY97 for each of the monitoring <br />wells can be found in tabular form in Appendix G. Water quality values for total dissolved <br />solids (TDS), iron (Fe) and manganese (Mn) are discussed because they are the most likely <br />constituents to be affected by mining activities. However, concentration changes for these <br />parameters may be of a natural consequence and not the result of mining. <br />Of the thirty-two wells that are currently part of the groundwater monitoring program, valid data <br />could not be collected from nine wells during WY97. Of these, five wells were blocked or had <br />pinched casings (SOM-38-H-], SOM C-72-H, JMB-12, So.W-3, LP-1), two were destroyed <br />(GB-] and GP-]), and two had interference of water from sources outside the formation of <br />interest (SOM-23-H-1 and SOM-23-H-2). In addition, nine wells were dry or had insufficient <br />water for water quality samples (GP-3, GP-4, GP-5, B-32, SW-1, SW-2, SW-4, SW-5 and SW- <br />6). These statistics (nine of thirty-two wells having insufficient water for sampling) are <br />• consistent with the general lack of groundwater within the Mesa Verde Formation. <br />The remaining fourteen wells had an adequate amount of water for sampling and little or no <br />casing damage. In general, the groundwater monitoring program data show the continuation of <br />trends (i.e., dry observations when previously dry, insufficient water for sampling as reported <br />previously, continued increases or decreases as previously observed, etc.) that originated prior to <br />WY97. <br />Alluvial and colluvial Wells <br />There aze currently five monitoring wells which are completed in alluvial or colluvial (i.e., <br />unconsolidated) materials. These include: GB-1 and GP-1 in the Sylvester Gulch alluvium and <br />GP-3, GP-4 and GP-5 in the colluvium underlying the lower refuse pile. <br />Both GB-1 (a replacement of well SG-1 described in previous reports) and GP-1 aze completed <br />to a depth of greater than 50 feet and show seasonal fluctuations which pazallel the surface water <br />hydrographs of the ephemeral streams which aze tributary to the North Fork in this area. Neither <br />of these wells provided data during WY97 because they had been destroyed by construction of <br />the lower refuse pile. Wells GP-6 and GP-7 were installed in October 1997 as replacements and <br />will continue monitoring of the alluvium in WY98. <br />Wells GP-3, GP-4 and GP-5 were completed in the colluvial material underlying the Lower <br />• Refuse Pile to monitor the potential migration of groundwater that could develop in and move <br />through the waste material. While water level observations within these wells have been <br />83l- 3 .450 Page Wrig t aver Engineers <br />