2000-03-15_PERMIT FILE - C1981010 (2)

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• SECTION 2.0 Annual Hydrology Report for Trapper Mine (1999) 2.1 Climatological Data The 1999 National Weather Service Cooperative monthly summaries and the historical precipitation sum- mary(1978-1999) are included in Section 2.5. 1999 precipitation totaling 15.64", provided 115 percent of the established historical pre-mining (44-YR) annual precipitation mean (Figure 2-1). The highest monthly precipitation amount was recorded in April (3.44") with the second highest total occurring in May (1.88"). The April precipitation was approximately twice the project-to-date average for the month while May precipitation was approximately normal. In terms of project-to-date monthly average precipitation amounts, August was the second wettest month following May with approximately 1.5 times normal precipitation. The year 1999 ended with drier than usual weather prevailing. September, October, November, and December precipitation values were all well below the project-to-date averages for these months. 2.2 Pit Dewatering and Consumptive Water Use for 1998 During 1999, Trapper dewatered approximately 73 acre-feet of water from two active pits. (Table 1-1 of Section 2.5 shows the pumping volumes for each pit). No additional dewatering from wells in Derringer or Flintlock pit occurred during 1999. The dewatering wells in the Derringer and Flintlock pits were rendered inoperable during 1998 as mining operations progressed beyond their areas of influence. All pit water was routed into the NPDES drainage system with resulting discharges monitored accordingly. Pit dewatering volumes were just slightly lower in 1999 than the 1998. Approximately 72 acre-feet of water were used for dust suppression on haul roads and topsoil handling operations in 1999. This quantity compares well with the 1998 total and remains elevated relative to prior • years due to the continued extension of haulroads into the Flintlock pit area and further movement of the mine to the east in Ashmore East pit. As previously noted, the fall months of 1999 were drier than usual causing higher than normal water demand for dust suppression during these months. Total water volume used by Trapper Mine in 1999 was approximately 146 acre-feet, lower than the 1998 total primarily due to the lack of well dewatering. 2.3 Mining Advancement and Ash Disposal Sites The 1999 Annual Hydrology Report maps depict the following mining activities through year end: a) Project to date utility waste disposal sites. b) Project to date pit advancement(foe of pit). c) Project to date monitoring and dewatering wells; and natural and spoil springs and seeps. In the 1999 report, all spring and seep sites within the permit area are depicted to provide location information for future reference. Sites that exhibited flows exceeding 5 gpm during the reporting year are distinguished from sites exhibiting flows less than 5 gpm. Three maps (Annual Hydrologic Report Map 2, Sheets 1, 2, ✓# 3) are provided to present this information. These maps include the locations of monitoring wells that are proximal to active mining and that could be affected in this permit term. 2.4 Monitoring Points Rather than submitting an additional map series, please refer to current Permit No. 0-81-010, Map M52, for locations of all the operational hydrologic monitoring points. No new ground water monitoring wells were installed during the 1999. • An additional NPDES discharge point (East Middle Flume Gulch) was completed during October of 1999. This pond did not discharge during the year. No new pit dewatering wells were installed during 1999.