2012-03-15_REPORT - C1981010 (8)

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2011 Annual Hydrology Report for Trapper Mine 2.1 Climatological Data RECE MAR 15 2012 k The 2011 National Weather Service Cooperative monthly summaries and the historical precipitation summary (1978 -2011) are included in Section 2.5. 2011 precipitation totaled 18.81 ", providing 139 percent of the established historical pre- mining (44 -YR) annual precipitation mean and 113 percent of the project -to -date annual precipitation mean (Figure 2 -1). The highest monthly precipitation amount was recorded in April (3.64 ") with the second and third highest totals occurring in May and March (3.37" and 1.78 ", respectively). 2.2 Pit Dewatering and Consumptive Water Use for 2011 During 2011, Trapper dewatered approximately 48.38 acre -feet of water from four active pits and 50.92 acre -feet of water from G -Pit dewatering wells. (Table 1 -1 of Section 2.5 sub - section 1.0 shows the pumping volumes for each activity). The dewatering wells are expected to produce at approximately the same rates for 2012. All pit water was routed into the NPDES drainage system with resulting discharges monitored accordingly. Pit dewatering volumes were slightly higher due to a heavy snow year, yet comparable to previous years. Approximately 234 acre -feet of water was used for dust suppression on haul roads and topsoil handling operations in 2011. This value appears to continue to rise during the past few years. Part of this consumption was the disposal of water from A -Pit. As A -Pit has filled with water the past few years, it could not all be pumped off -site. Water was utilized from the pit for dust suppression or was dumped from water trucks in the road ditches. Dust suppression water demands continue to be somewhat offset by the successful application of dust suppression chemical treatments on haulroads. Haul routes were similar in 2011 to 2010 routes. Life -of -mine Haulroad is still the primary route for coal delivery to the Craig Station. Continued activity in the eastern portion of the mine accounts for increased water usage also. This is due to heavy activity in the active stripping of the east panel with a truck and wheeled loader fleet. Total water volume used by Trapper Mine in 2011 was approximately 333 acre -feet, a significant increase over 2010 consumption at 239 acre feet. 2.3 Mining Advancement and Ash Disposal Sites The 2011 Annual Reclamation maps (see Trapper's 2011 annual report), the Water -Level Elevation maps 2 -1, 2 -2 and 2 -3 (included in this report) , and permit Map M52 (see mine permit) depict the following mining activities through year -end: a) Project to date utility waste disposal sites. b) Project to date pit advancement (toe of pit). c) Project to date monitoring wells, and natural and spoil springs and seeps. In the 2011 report, all spring and seep sites within the permit area are depicted to provide location information for future reference. 2.4 Monitoring Points Refer to Map M52 in the mine permit for locations of all the operational hydrologic monitoring points. No new ground water monitoring wells were installed during 2011.