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POWDERHORN COAL COMPANY <br />1998 ANNUAL HYDROLOGIC REPORT <br />AND MINE INFLOWS STUDY <br />OCTOBER 1, 1997 THROUGH SEPTEMBER 30, 1998 <br /> <br />'• <br />1 <br />1 <br />1 <br />1 <br />1~ <br />Q <br />4 <br />Introduction <br />During the 1998 Water Year, the Year, the Roadside South Portal did not operate. The <br />Roadside North Portal operated the entire Year. Production at the Roadside North utilized <br />room and pillar mining with a continuous miner and shuttle cars. <br />The Peabody Western's hydrologic reporting system was not available for use. Data and <br />diagrams from system for the 1997 report are presented in this report for a comparison of <br />trends. 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 <br />located upstream approximately 7 miles north east of the mine site. Water quality and flow <br />from this site i~~ 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-20 and 21 include information supplied by USGS on this <br />site in 1998. The total flow at this site for the Year was 3,062,000 acre-feet which amounts <br />to 108% of the 1934-1998 average flow. The estimated TDS load for the Year was 1.809 <br />million tons. This estimate is made using the value for dissolved solids reported on page <br />SQ-21 times the monthly flow in acre feet. The low flow for the Year was recorded as 2010 <br />CFS on December 13, 1997. As can be seen on data page SQ-21, the river was carrying <br />0.73 tons of TDS per acre-foot on December 10, 1997. This flow and TDS load equates <br />to approximately 1,467 tons of Total Dissolved Solids, TDS, being carried by the river past <br />the mine that day. Mine discharges on December 15, 1997 (the closest monthly analysis), <br />were: 001 - No Discharge in December; 002 - 70 GPM @ 1396 mg/l TDS; and 004 - 290 <br />GPM @ 1381 mg/I TDS, resulting in approximately 2.99 tons of TDS being discharged. <br />Comparing the calculated TDS load in the River at low flow and the mine discharge near <br />the same date, the maximum increase in the River's TDS as a result of mine discharge <br />would have been 0.20°h. <br />AHR 98 Page 1 5-1-99 <br />