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• POWDERHORN COAL COMPANY 1996 ANNUAL HYDROLOGIC REPORT AND MINE INFLOWS STUDY OCTOBER 1,1995 THROUGH SEPTEMBER 30,1996 Introduction During the 1996 Water Yeaz, the Yeaz, the Roadside South Portal and the Roadside North Portal were both being operated. Production at the Roadside North continued to be done using room and pillar mining with•a continuous miner and shuttle cazs. Production at the Roadside South continued with development only using a continuous miner and continuous haulage. Both mines had difficult geologic, hydrologic and gas problems. The Peabody Western's hydrologic reporting system again was used as a tool for compiling and reporting part of the information for this Yeaz's report. The general format of this report is the same as in previous years. This reporting period includes monitoring requirements which were added to our Mining and Reclamation Permit to cover springs and creeks on the Roadside North portions of the permit area. • Surface Water Water flow and quality on the Colorado River is monitored by the U.S. Geologic Survey (USGS) at various locations. The closest location is Station No. 09095500 which is located upstream approximately 7 miles north east of the mine site. Water quality and flow from this site aze used as a general representation of the Colorado River up gradient of our mining operation. There is a diversion to the Government Highline Canal, the addition of Plateau Creek and the addition of other minor drainages between the monitoring site and the mine site. Data Pages SQ-13 thru 17 include information supplied by USGS on this site in 1996. The total flow at this site for the Yeaz was 3,464,000 acre-feet which amounts to 123% of the 1934-1996 average flow. The estimated TDS load for the yeaz was 1.666 million tons. This estimate is made using the sum of the monthly average conductivity times monthly flow times a calculated conductivity -tons/a.f. ratio. A conductivity - tonsla.f. ratio of 0.000829 was calculated from information on data pages SQ-14 thru -17. The low flow for the year was recorded as 1880 CFS on February 4, 1996. As can be seen on data page SQ-16, the conductivity recorded this day was 992 umhos/cm. This flow and conductivity equates to approximately 3067 tons of Total Dissolved Solids, TDS, being carried by the river past the mine that day. Mine discharges on January 24, 1996 (the closest monthly analysis), were: 001 - O GPM; 002 - 181 GPM @ 1660 mg/I TDS; and 004 - 99 GPM @ 2170 mg/1 TDS, resulting in approximately 3.079 tons of TDS being dischazged. Comparing the calculated TDS load in the • River at low flow and the mine dischazge neaz the same date, the maximum increase in the River's TDS as a result of mine dischazge would have been 0.10%.