2016-03-11_REPORT - C1981010 - Laserfiche WebLink

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2015 Annual Hydrology Report for Trapper Mine 2.1 Climatological Data The 2015 National Weather Service Cooperative monthly summaries and the historical precipitation summary (1978-2015) are included in Section 2.5. For the year of 2015 precipitation totaled 17.30", providing 128 percent of the established historical pre -mining (44 -YR) annual precipitation mean and 105 percent of the project -to -date annual precipitation mean (Figure 2-1). The highest monthly precipitation amount was recorded in May (3.93") with the second and third highest totals occurring in December and July (2.60" and 1.89", respectively). 2.2 Pit Dewatering and Consumptive Water Use for 2015 During 2015, Trapper dewatered approximately 32.41 acre-feet of water from two active pits and 50.74 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 2015. All pit water was routed into the NPDES drainage system with resulting discharges monitored accordingly when pumped off site. The majority of pumped water was utilized on haulroads for dust suppression. Approximately 215.30 acre-feet of water was used for dust suppression on haul roads and topsoil handling operations in 2015. This value increased slightly this year compared to last year but is around the average from the past few years. The majority of this water was utilized from A -Pit where water has been stored in the inactive pit. Dust suppression water demands continue to be offset by the successful application of dust suppression chemical treatments on haulroads. Haul routes were similar in 2015 to 2014 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 the majority of dust suppression water usage. Reduction in temporary haul routes through the slide has helped reduce some water consumption on dust suppression. However, a dry June accounted for highest use during the year and the increase over last year. Total water volume used by Trapper Mine in 2015 was approximately 298 acre-feet, a slight decrease over 2014 consumption at 302 acre feet. 2.3 Mining Advancement and Ash Disposal Sites The 2015 Annual Reclamation maps (see Trapper's 2015 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 2015 report, all applicable 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. Three new ground watering wells were initiated during the 1s' quarter of 2015. GLEV1, 2 and 3 are located in the northeastern corner of the permit area in the recently expanded PR -07 area. They will be used to monitor ground water quality for the eastern area of the mine in the Alluvium (GLEV-2), HI interval (GLEV-3) and the QR interval (GLEV-2).