2020-03-19_REPORT - C1981010 (7)

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2019 Annual Hydrology Report for Trapper Mine 2.1 Climatological Data The 2019 National Weather Service Cooperative monthly summaries and the historical precipitation summary(1978-2019)are included in Section 2.5. For the year of 2019 precipitation totaled 17.83", providing 131 percent of the established historical pre-mining (44-YR)annual precipitation mean and 108 percent of the project-to-date annual precipitation mean (Figure 2-1). The highest monthly precipitation amount was recorded in March (2.70")with the second and third highest totals occurring in June and December(2.66" and 2.09", respectively). Conversely the lowest monthly precipitations occurred in July, August and September at 0.38", 0.45" and 0.58". 2.2 Pit Dewatering and Consumptive Water Use for 2019 During 2019, Trapper dewatered approximately 26.69 acre-feet of water from L-Pit and 34.68 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 2020. All pit water was routed into the NPDES drainage system with resulting discharges monitored accordingly when pumped off site. In 2019, all of the pumped water was utilized on haulroads for dust suppression. Approximately 185.91 acre-feet of water was used for dust suppression on haul roads and topsoil handling operations in 2019. This value decreased 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 2019 to 2018 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. Total water volume used by Trapper Mine in 2019 was approximately 247 acre-feet, a slight decrease over 2018 consumption at 269 acre feet. 2.3 Mining Advancement and Ash Disposal Sites The 2019 Annual Reclamation maps (see Trapper's 2019 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 2019 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.