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L INTRODUCTION <br />The purpose of this report is to provide updated information pertaining to the on-going hydrologic monitoring <br />program developed for the Edna Mine and discuss trends in surface and ground water quality which have become evident <br />' over the past decade. The previous report, dated February 2004, reported monitoring activities up through the end of 2003. <br />This report discusses data for parameters which have been collected on an on-going basis for the period 1995 through 2004. <br />The report is divided into several sections including: Hydrologic Monitoring Network; Surface Water; Ground <br />Water; Surface Water-Ground Water Interactions; Quality Assurance; Annual Spring and Seep Survey; Moffat Stability; and <br />_ Trout Creek Sandstone. A compilation of [he raw data is provided in the Appendices. <br />IL HYDROLOGIC MONITORING NETWORK <br />The present monitoring network is a modification of the network used during baseline monitoring. Continuous <br />streamflow records are made For Trout Creek above the mine (TR-a) from May through October (periods of freezing <br />sometimes necessitate the records to be of shorter duration). Instantaneous streamflow was recorded on Trout Creek below <br />' the Moffat mining area at TR-b prior to July ] 994. During June 1994, a continuous streamflow recorder was installed a[ TR- <br />b. Therefore, monitoring data after June 1994 has been collected on the same schedule as at TR-a. Surface water samples are <br />collected above and below the mine at TR-A and TR-D, respectively. Additional surface water sampling sites along Trout <br />' Creek are TR-B (located adjacent to the East Ridge area) and TR-C (located adjacent to the Moffat area). Ground water <br />levels and samples are collected from three wells completed in the alluvium along Trout Creek (TR-1.5, TR-3 and TR-4) and <br />from a spoils well (WR-1) located at the base of the West Ridge azea. Additional ground water levels are collected from six <br />wells (215W, 215L, 218W, 218L, 8925 and 892L) located in the Moffat area. Finally, the Trout Creek Sandstone water <br />' quality is monitored downdip of mining activity via samples taken from Well TCS-1. All of the monitoring sites are shown <br />on Exhibit 4.6-26 of the permit document. <br />WATER QUALITY ANALYSES AND SAMPLING FREQUE]vCY <br />The samples are analyzed for the parameters listed in Table 4.6-54, Section 4.6.8.4 of [he permit. Sampling <br />frequency at the various sites is also listed in Table 4.6-54. Parameters measured in [he field include: pH, temperature, and <br />specific conductivity. All other parameters measured are analytically derived at an independent laboratory. Surface water <br />data are contained in Appendix A and ground water data are contained in Appendix B. <br />' III. SURFACE WATER <br />' GAUGING STATIONS <br />Figure 1 shows the continuous streamflow records for Trout Creek at TR-a and TR-b. The graphs showing the <br />