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2016 Annual Hydrology Report for Trapper Mine <br />2.1 Climatological Data <br />The 2016 National Weather Service Cooperative monthly summaries and the historical precipitation <br />summary (1978-2016) are included in Section 2.5. For the year of 2016 precipitation totaled 14.95", <br />providing 110 percent of the established historical pre -mining (44 -YR) annual precipitation mean and 91 <br />percent of the project -to -date annual precipitation mean (Figure 2-1). The highest monthly precipitation <br />amount was recorded in April (2.42") with the second and third highest totals occurring in May and <br />December (1.75" and 1.58", respectively). <br />2.2 Pit Dewatering and Consumptive Water Use for 2016 <br />During 2016, Trapper dewatered approximately 7.85 acre-feet of water from two active pits and 53.46 <br />acre-feet of water from G -Pit dewatering wells. (Table 1-1 of Section 2.5 sub -section 1.0 shows the <br />pumping volumes for each activity). The dewatering wells are expected to produce at approximately the <br />same rates for 2017. All pit water was routed into the NPDES drainage system with resulting discharges <br />monitored accordingly when pumped off site. The majority of pumped water was utilized on haulroads for <br />dust suppression. <br />Approximately 205.20 acre-feet of water was used for dust suppression on haul roads and topsoil <br />handling operations in 2016. This value decreased slightly this year compared to last year but is around <br />the average from the past few years. The majority of this water was utilized from A -Pit where water has <br />been stored in the inactive pit. Dust suppression water demands continue to be offset by the successful <br />application of dust suppression chemical treatments on haulroads. Haul routes were similar in 2016 to <br />2015 routes. Life -of -mine Haulroad is still the primary route for coal delivery to the Craig Station. <br />Continued activity in the eastern portion of the mine accounts for the majority of dust suppression water <br />usage. Reduction in temporary haul routes through the slide has helped reduce some water consumption <br />on dust suppression. Total water volume used by Trapper Mine in 2016 was approximately 267 acre- <br />feet, a slight decrease over 2015 consumption at 298 acre feet. <br />2.3 Mining Advancement and Ash Disposal Sites <br />The 2016 Annual Reclamation maps (see Trapper's 2016 annual report), the Water -Level Elevation maps <br />2-1, 2-2 and 2-3 (included in this report) , and permit Map M52 (see mine permit) depict the following <br />mining activities through year-end: <br />a) Project to date utility waste disposal sites. <br />b) Project to date pit advancement (toe of pit). <br />C) Project to date monitoring wells, and natural and spoil springs and seeps. In the 2016 report, all <br />applicable spring and seep sites within the permit area are depicted to provide location <br />information for future reference. <br />2.4 Monitoring Points <br />Refer to Map M52 in the mine permit for locations of all the operational hydrologic monitoring points. <br />Monitoring of groundwater well P-3 was discontinued during the third quarter of 2016 through Technical <br />Revision 115. An unknown failure of the casing had made the well unusable. The well was also <br />completed in the Lewis shale, a strata not typically disturbed at Trapper and far removed from any pit <br />limits. <br />