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iii iiiiiiiuiiu iii 999___ ~--- FJ I ~j Doc Date:1211112001 SECTION 2.0 Annual Hydrology Report for Trapper Mine (1995) Trapper Mine is providing the Division with an Annual Hydrology Report required by our approved mining permit (Section 4.8.5). 2.1 Climatological Data The 1995 National Weather Service Cooperative monthly summaries and the historical precipitation summary (1976-1995) are included in Section 2.5. 1995 was 148 percent of the historical precipitation mean and was the third highest annual precipitation year since 1978 (Figure 2-1). 2.2 Pit Dewatering and Consumptive Water Use for 1995 During 1995, Trapper dewatered approximately 59 acre-feet of water from three active pits and an addi- tional 11 acre-feet from one dewatering well in Denrnger pit. Table 1-1 of Section 2.5 shows the pump- ing volumes for each pit. All pit water was routed into the NPDES drainage system and for the most part was lost to percolation and evaporation. Pit dewatering volumes were considerably higher than the 1994 total. Reasons for the high volume is attributed to the high precipitation year resulting in higher pit dewatering activities. Well dewatering in Deninger pit was less than the 1994 level due to the dewatering well being disconnected in early May and relocation was not complete till late September. This also contributed to higher pit dewatering levels. • Approximately 111 acre-feet of water were used for dust suppression on haul roads and topsoil handling operations in 1995. This higher use of water for dust suppression was in response to the low precipitation amounts received in July, August, and to the mid-part of September, which resulted in a more active dust suppression program. Total water volume used by Trapper Mine in 1995 was approximately 180 acre-feet. 2.3 Mining Advancement and Ash Disposal Sites The 1995 Annual Hydrology Report maps depict the following mining activities through year end a) Project to date (PTD) utility waste disposal sites. b) PTD pii advancement (roe of pit): c) PTD monitoring and dewatering wells; and all spoils seeps with flows that may exceed 5 gallons per minute (gpm). Two maps are provided, since mining has expanded into the East Panel, to include monitoring wells that are now proximal to active mining and that could be affected in this permit term. 2.4 Monitoring Points Rather than submitting an additional map series, please refer to the current Map 52 showing all the operational hydrologic monitoring points. No new ground water monitoring wells were installed during the year. An additional NPDES point, Oak Gulch (NPDES 017) was initiated during the year. The installation was not completed due to weather conditions but will be finished in 1996. One new dewatering well was drilled in the Derringer pit area and was operational late September (Well No. 7). Another dewatering well, (No. 8) was drilled in Derringer Pit in December but did not become