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~I ~' III IIIIIIIIIIIIIIII 999 Doc Date:12/11/2001 ;: SECTION 2.0 Annuaf Hydrology Report for Trapper Mine (1997) 2.1 Climatological Data The 1997 National Weather Service Cooperative monthly summaries and the historical precipitation sum- mary (1978-1997) are included in Section 2.5. 1997 was 161 percent of the historical precipitation mean (Figure 2-1). A significant portion of this total occurred in September in association with a storm pattern which resuRed in over five inches of rainfall for the month. 2.2 Pit Dewatering and Consumptive Water Use for 1997 During 1997, Trapper dewatered approximately 72 acre-feet of water from three active pits and an addi- tional 46 acre-feet from two dewatering wells in Derringer 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 with resuRing discharges monitored accordingly. Pit dewatering volumes were slightly lower in 1997 than the 1996 totals and would likely have been significantly lower but for the September rainfall event discussed previously. Well dewatering overall in 1997 was higher than in 1996 due to the added contributions from the Flintlock pit wells. Derringer pit well dewatering totals for 1997 were comparable to those recorded in 1996. Approximately 53 acre-feet of water were used for dust suppression on haul roads and topsoil handling operations in 1997. This lower use of water for dust suppression is partially attributed to the use of magnesium chloride treatments on haulage routes in 1997, although numerous other variables affect the • total volume of water used for dust suppression. Total water volume used by Trapper Mine in 1997 was approximately 170 acre-feet, slightly lower than the 1996 total. 2.3 Mining Advancement and Ash Disposal Sites The 1997 Annual Hydrology Report maps depict the folbwing mining activities through year end: a) Project to date utildy waste disposal sites. b) Project to date pit advancement (Toe of pit). c) Project to date monitoring and dewatering wells; and natural and spoil springs and seeps with Oows. Two maps are provided to present this information, including the monitoring wells that are proximal to active mining and that could be affected in this pennfl tens. 2.4 Monitoring Points Rather than submitting an additional map series, please refer to the current Map M52 showing all the operational hydrologic monitoring points. No new ground water monitoring wells were installed during the year. NPDES discharge point 019 (West Flume Gulch) was completed during the fall of 1997 year. However, the pond did not discharge during the year. • As mentioned previously, two new wells drilled in the Flintlock pit area in 1996 were operational during the last half of 1997.