2008-03-14_REPORT - C1981010 (5)

Home Browse Search

~~~~~~~~ 2007 Annual H~ for Trapper Mine 2.1 Climatological Data pivis-u-nngwand 5afe~n~ The 2007 National Weather Service Cooperative monthly summaries and the historical preciipita~tion summary (1978-2007) are included in Section 2.5. 2007 precipitation totaled 19.82", providing 146 percent of the established historical pre-mining (44-YR) annual precipitation mean and 120 percent of the project-to-date annual precipitation mean (Figure 2-1 ). The highest monthly precipitation amount was recorded in December (4.13") with the second and third highest totals occurring in September and October (3.89" and 2.49", respectively). 2.2 -Pit Dewatering and Consumptive Water Use for 2007 During 2007, Trapper dewatered approximately 34.52 acre-feet of water from four active pits and 44.87 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 2008, or may decline depending on mine progress. All pit water was routed into the NPDES drainage system with resulting discharges monitored accordingly. Pit dewatering volumes were slightly higher in 2007 as compared to 2006 due to several intense precipitation events during the year. Approximately 89 acre-feet of water were used for dust suppression on haul roads and topsoil handling operations in 2007. This value is higher than 2006 values at 74 acre feet, but well within the normal range of water usage on the site. 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 2007 as 2006. However increased activity in the eastern portion of the mine may have accounted for increased water usage. Total water volume used by Trapper Mine in 2007 was '" approximately 168 acre-feet, slightly higher than 2006 consumption at 150 acre feet. 2.3 Mining Advancement and Ash Disposal Sites The 2007 Annual Reclamation maps (see Trapper's 2007 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 2007 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 2007. Well GP-6 was not abandoned as planned in 2007 due to inclement weather, but will be abandoned in 2008. Well 81-03A will need further investigation for proper abandonment in the future as it is a flowing well. Well GF-3 is currently plugged and has not shown any signs of leakage or flow. This well had previously been problematic during abandonment procedures. •