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III IIIIIIIIIIIII III Doc Date:1 211 1 /2 0 01 <br />sss <br />`Jl~ SECTION 2.0 Annual Hydrology Report for Trapper Mine (1991) <br />Trapper Mine is providing CMLRD with an Annual Hydrology Report (AHR) required by our approved <br />mining permit (Section 4.8.5). <br />2.1 Climatological Data <br />The 1991 National Weather Service (NWS) Cooperative monthly summaries and the historical precipitation <br />summary (1979-1992) are included in Section 2.5. Trapper has been the official NOAH station near Craig, <br />Colorado since 1979. The yearly precipitation totals for the past Crve years have been near average or below <br />average for this vicinity. 1991 was only 95 percent of the historical mean (13.56") and the thud year in the <br />last four with below-average annual precipitation (see Figure 2-1). <br />2.2 Pit Dewatering and Consumptive Weter Use for 1991 <br />During calendar 1991, Trapper conventionally pumped (dewatered) approximately 146 acre-feet of water <br />from four active pits and an additiona160 acre-feet from the two active mine dewatering weLLs in Derringer <br />(D) and Browning (B) pits. Table 1-1 (Section 2.5, page 1-3) shows the annual pumping volumes for each <br />pit. All pit water was routed into the NPDES drainage systems and for the most part was lost to percolation <br />• and evaporation. Limited amounts continued downsveam to the Yampa River. <br />As previously mentioned, dewatering well volumes from the boxcut toe and spoils in B and D pits totaled <br />approximately 60 acre-feet. There were no additional wells installed in D pit during 1991. Two wells were <br />installed in B pit but onty one (B2) was active during 1991. See Table 1.1 for discharge volumes. Installation <br />specifications were the same as those submitted in Appendix W (1988) figures 2.2-1 to 2.2-0). <br />Approximately 59 acre-feet of water were used during 1991 for dust suppression on the haul roads and top- <br />soil salvage operations. The total water volume utilized by Trapper Mine during 1991 was approximately <br />264 aae-feet. <br />2.3 Mining Advancement and Ash Disposal Sites <br />The 1991 Annual Hydrology Report (AHR) maps depict the following mining activities through year end: <br />a) Project to date (PTD) utility waste disposal sites. <br />b) PTD pit advancement (Toe of pit). <br />c) PTD monitoring and dewatering wells; and all spoils seeps with flows >5 gallons per minute (gpm). <br />Two maps are provided, since mining has expanded into the Fast Panel, to include monitoring wells that are <br />now proximal to active mining and that could be effected in the next permit term. <br /> <br />