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Site Descriptions <br />Surface Water Table 15-2, Summary of Surface Water Monitoring Sites, Yoast Mine, provides a description <br />of all historic and current surface water and spring monitoring sites. <br />Ground Water Table 15-3, Summary of Ground Water Monitoring Sites, Yoast Mine, provides a summary <br />of all historic and current ground water monitoring sites. Wells with USGS numbers on Table 15-3, <br />Summary of Ground Water Monitoring Sites, Yoast Mine, were drilled and completed in the summer of 1980 <br />by the USGS. All remaining wells were drilled and completed in the summer of 1990 by PWCC. Well <br />construction summaries and lithologic logs are found in Appendix 7-1, Well Completion Summaries, Well <br />Construction Diagrams, and Lithologic logs. <br />Development procedures for the 1980 USGS wells were not documented. However, the act of purging <br />water for water quality sampling will have developed these wells by the removal of sediment in the well <br />casing, screen, and gravel pack. Development procedures for the 1990 PWCC wells consisted of air <br />surging, bailing, and/or pumping. <br />Aquifer tests were performed on most wells completed in 1990 and also for selected USGS wells (see <br />Table 7-9, Site Specific Aquifer Characteristics for Yoast Mine). Aquifer tests were not performed on Wells <br />YOV29 and YWCU31 due to a lack of water. Aquifertest data is discussed in Tab 7, Hydrologic Description <br />and is presented in Appendix 73, Aquifer Test Data. <br />Monitoring Frequencies <br />The current monitoring program was established after a review of the hydrologic data presented in the <br />Hydrologic Description (Tab 7, Hydrologic Description) and [he Probable Hydrologic Consequences (Tab <br />17, Probable Hydrologic Consequences). Data in those lwo tabs indicated that mining will have little impact <br />on water-bearing bedrock strata (i.e., Wadge coal, overburden, and underburden) downdip of mining. <br />These bedrock strata typically have poor water quality and yields. Also, better aquifers (i.e., the Twentymile <br />and Trout Creek Sandstones) exist both above and below the Wadge coal (see Geologic Description in Tab <br />6, Geology and Overburden Assessment), and will remain undisturbed for potential future use. More <br />significant will be the impacts on the alluvial aquifers and streams, and therefore, monitoring of those <br />systems will be emphasized. <br />I• <br />20 Revised 2/99 <br />