2007-03-16_REPORT - C1981010 (5)

Home Browse Search

2006 Annual Hydrology Report for Trapper Mine 2.1 Climatological Data The 2006 National Weather Service Cooperative monthly summaries and the historical precipitation summary (1978 -2006) are included in Section 2.5. 2006 precipitation totaling 17.18 ", provided 127 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 September (3.49 ") with the second and third highest totals occurring in October and March (3.18" and 2.44" respectively). 2.2 Pit Dewatering and Consumptive Water Use for 2006 During 2006, Trapper dewatered approximately 28.65 acre -feet of water from four active pits and 47.23 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 2007, 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 2006 as compared to 2005 due to several intense precipitation events during the year. Approximately 74 acre -feet of water were used for dust suppression on haul roads and topsoil handling operations in 2006. This value is higher than 2005 values at 69 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 2006 as 2005. 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 2006 was approximately 150 acre -feet, similar to 2005 consumption of 140 acre feet. 2.3 Mining Advancement and Ash Disposal Sites The 2006 Annual Reclamation maps (see Trapper's 2006 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 2006 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 2006. Six ground water monitoring sites will no longer be monitored after 2006. Wells 81 -03A, GE -1, GE -2, GE -3, GLUX -1, and GP -6 are abandoned and or will be abandoned. Due to Phase III bond released lands up gradient of the sites and inactivity in their proximities they will no longer be monitored. Wells GE -1 thru 3 and GLUX -1 were completely abandoned in 2006. Well GP -6 will be abandoned in 2007. Well 81 -03A will need further investigation for proper abandonment in the future as it is a flowing well. Well GF -3 is still experiencing surface flow from the top of the casing and was not abandoned in 2006 as planned. Attempts at abandonment failed and new methods will be tried in 2007 to fully abandon the well. It is a flowing well and has proven difficult to seal, due to this, we are investigating the best course of abandonment for 81 -03A.