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i~ <br />• <br />POWDERHORN COAL COMPANY <br />1999 ANNUAL HYDROLOGIC REPORT <br />AND MINE INFLOWS STUDY <br />OCTOBER 1, 1998 THROUGH SEPTEMBER 30, 1999 <br />Introduction <br />During the 1999WaterYear, the Year, the Roadside South Portal was idle. The Roadside <br />North Portal operated the entire Year. Production at the Roadside North utilized room and <br />pillar mining with a continuous miner and shuttle cars. The general format of this report <br />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-22 and 23 include information supplied by USGS on this <br />site in 1999. The total flow at this site for the Yearwas 2,767,000 acre-feet which is about <br />the normal average flow for the period 1934 -1998 (2,843,000). The estimated TDS load <br />for the Year was 1.4 million tons. This estimate is made using the values for dissolved <br />solids reported on page SQ-23 times the monthly flow in acre feet. The low flow for the <br />Year was recorded as 1400 CFS on December 23, 1998. The river was carrying <br />approximately 0.83 tons of TDS per acre-foot on December 23rd. This flow and TDS load <br />equates to approximately 2,300 tons of Total Dissolved Solids, TDS, being carried by the <br />river past the mine that day. Mine discharges on December 14, 1998 (the closest monthly <br />analysis), were: 001 -120 GPM @ 779 TDS; 002 -190 GPM @ 1558 mg/I TDS; and 004 <br />- 240 GPM @ 1444 mg/I TDS, resulting in approximately 4.42 tons of TDS being <br />discharged. Comparing the calculated TDS load in the River at low flow and the mine <br />discharge near the same date, the maximum increase in the River's TDS as a result of <br />mine discharge would have been 0.19%. <br />This Year's mean daily flow values for the Cottonwood and Rapid Creek flumes are <br />• included on data pages SG-27, SH-25, SI-25 and SK-11. Flowat SWGS-001 is presented <br />graphically on data page SG-28. As usual, the flow in these Creeks is largely controlled <br />by the City of Palisade, depending upon their need for domestic water. Also, irrigation <br />