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' / III I II I II I II IIII III Doc Date:12/1112001 _ /I](/// SECTION 2.0 Annual Hydrology Report for Trapper Mine (1994) Trapper Mine is providing the Division with an Annual Hydrology Report required by our approved mining permit (Section 4.8.5). 2.1 Climatological Data The 1994 National Weather Service Cooperative monthly summaries and the historical precipitation summary (1979-1994) are included in Section 2.5. 1994 was 83 percent of the historical precipitation mean and was the second lowest annual precipitation year since 1978 (Figure 2-1). 2.2 Pit Dewatering and Consumptive Water Use for 1994 During 1994, Trapper dewatered approximately 21 acre-feet of water from three active pits and an additional 13 acre-feet from one dewatering well in Derringer pit. Table 1-1 of Section 2.5 shows the pumping volumes for each pit. All pit water was routed into the NPDES drainage system and for the most part was lost to percolation and evaporation. Pit dewatering volumes were considerably lower than the 1993 total. Reasons for the low volume were: 1) only one dewatering well was active ,and 2) the extremely low precipitation year resulted in low pit dewatering activities. • Approximately 81 acre-feet of water were used for dust suppression on haul roads and topsoil handling operations in 1994. The low use of water for dust suppression was due to the aggressive use of mag- nesium chloride (MgCI) on haul roads. Additionally, the dry weather retarded the degradation of the MgCI, which required less road water applications. Total water volume used by Trapper in 1994 was approximately 116 acre feet. 2.3 Mining Advancement and Ash Disposal Sites The 1994 Annual Hydrology Report maps depict the following mining activities through year end a) Project to date (PTD) utility waste disposal sites. b) PTD pit advancement (Toe of pit). c) PTD monitoring and dewatering wells; and all spoils seeps with flows >5 gallons per minute (gPm)~ Two maps are provided, since mining has expanded into the East Panel, to include monitoring wells that are now proximal to alive mining and that wuld be affected in this permit tens. 2.4 Monitoring Points Rather than submitting an additional map series, please refer to the current Map 52 showing all the operational hydrologic monitoring points. No new ground water monitoring wells were installed during the year. An additional NPDES point, Sage Gulch (018), was added during the year. No new pit dewatering wells were constructed in 1994. In 1994, NPDES points 003, 006 and 014 were changed from active to post-mining use by the Water Quality Control Division. As a result, sampling requirements in accordance with NPDES Permit CO- 0032115 were revised. Permit Tables 4.8-11 and 4.8-12a have been revised to reflect these changes. ~T(c-66 ~/s~/qd