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i~ <br />• <br />POWDERHORN COAL COMPANY <br />2000 ANNUAL HYDROLOGIC REPORT <br />OCTOBER 1, 1999 THROUGH SEPTEMBER 30, 2000 <br />Introduction <br />During the 2000WaterYear, the Year, the Roadside South Portal was idle. Mining ceased <br />at the Roadside Portals on December 2, 1999. The North Mine was sealed on February <br />10, 2000. The Roadside South Mine was sealed on April 12, 2000. The South Fan was <br />sealed May 22, 2000. The 2 West Portals were sealed on April 24, 2000. Production at <br />the Roadside North utilized room and pillar mining with a continuous miner and shuttle <br />cars. The general format of this report is the same as in previous years. <br />Surface Water <br />Water flow and quality on the Colorado River is monitored by the U.S. Geologic Survey <br />(USGS) at various locations. The closest location is Station No. 09095500 which is located <br />upstream approximately 7 miles north east of the mine site. Water quality and flow from <br />this site are used as a general representation of the Colorado River up gradient of the <br />mining operation. There is a diversion to the Government Highline Canal, the addition of <br />Plateau Creek and the addition of other minor drainages between the monitoring site and <br />the mine site. Data Pages SQ-24 and 25 include information supplied by USGS on this <br />site in 2000. The total flow at this site for the Year was 2,332,000 acre-feet which is 82% <br />of the normal average flow for the period 1934 -2000 (2,835,000). The estimated TDS <br />load for the Year was 1.2 million tons. This estimate is made using the values for dissolved <br />solids reported on page SQ-25 times the monthly flow in acre feet. The low flow for the <br />Year was recorded as 1,470 CFS on December 16, 1999 and again on January 08,2000. <br />The river was carrying approximately 0.84 tons of TDS per acre-foot on December 16`h. <br />This flow and TDS load equates to approximately 2,450 tons of Total Dissolved Solids, <br />TDS, being carried by the river past the mine that day. Worst case mine discharges <br />occurring on December 01, 1999 (the closest monthly analysis), were: 001 - 300 GPM @ <br />729 mg/I TDS; 002 - 210 GPM @ 1576 mg/I TDS; and 004 - 170 GPM @ 1585 mg/I TDS, <br />resulting in approximately 4.92 tons of TDS being discharged. Comparing the calculated <br />TDS load in the River at low flow and the mine discharge near the same date, the <br />maximum increase in the River's TDS as a result of mine discharge would have been <br />0.21 %. <br />