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III I II I II I II I'll'll Doc Date:12l11l2001 sss • ~7I~jSECTION 2.0 Annual Hydrology Report for 7Y~apper Mine (1992) Trapper Mine is providing OMLR with an Annual Hydrology Report required by our approved mining permit (Section 4.8.5). 2.1 Climatological Data The 1992 National Weather Service Cooperative monthly summaries and the historical precipitation sum- mary (1979-1992) are included in Section 2.5. 1992 was 123 percent of [he historical mean (13.56") and was the highest annual precipitation year since 1986 (Figure 2-1). 2.2 Pit Dewatering and Consumptive Water Use [or 1992 During calendar 1992, Trapper dewatered approximately 52 acre-feet of water from four active pits and an additional 53 acre-feet from two dewateting wells in Derringer pit and one well in ESrowning pit Table 1-1 of Section 2.5 shows the pumping volumes for each pit All pit water was routed into the NPDFS drainage system and for the most part was lost to percolation and evaporation. • Approximatety SO acre-feet of water were used for 1992 dust suppression on haul roads and topsoil salvage operations. Total water volume used by Trapper during 1992 was approximatety 185 acre-feet Dewatering well volumes from the boxwt toe and spoils in B and D pits totaled approximately 42 acre-feet One new well (No. 6) was installed in D pit B pit also had a well (No. 3) installed in 1992. Installation specifications were the same as those presented in Appendix W (1988) Figures 2.2~ 1 and 2.2~. Table 1.1 presents discharge volumes for the dewatering wells in 1992. 2.3 Mining Advancement and Ash Disposal Sites The 1992 Annual Hydrology Report maps depict the following mining activities through year end: a) Project to date (PTD) utility waste disposal sites. b) PTD pit advancement (Toe of pit). c) PTD monitoring and dewatering wells; and all spoils seeps with flows >5 gallons per minute (gpm). Two maps are provided, since mining has expanded into the Fast Panel, to include monitoring wells that are now proximal to active mining and that could be affected in the next permit term. 2.4 Monitoring Points PTD • Rather than submitting an additional map series, Trapper refers the Division to the current Map 52 showing all the operational hydrologic monitoring points. One new dewatering well was constructed in North Browning pit, and one in Derringer pit during 1992.