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Discharge values collected from surface water monitoring sites at the Nucla Mine during <br />the 1991 water year are presented in Appendix A. This appendix also contains select <br />hydrographs constructed from the discharge data. Water quality data collected at Nucla <br />Mine surface water monitoring sites can be found in Appendix C. <br />Monitoring activities conducted at the Nucla Mine during the 1991 water year included <br />compliance monitoring as outlined in Peabody's amended NPDES Permit No. C0- 0000213 at <br />outfalls 001, 002, 003, 004, 005 and 006. Appendix B contains Discharge Monitoring <br />Reports (DMR's) for each outfall for the fourth quarter of 1990, and the first, second, <br />and third quarters of 1991. Discharge measurements collected at NPDES Site 006 <br />(instantaneous) and NPDES Site 001 (continuous and instantaneous) during the 1991 water <br />year are presented in Appendix A. <br />During the 1991 water year, spoil spring surveys were conducted within and adjacent to the <br />Nucla permit boundary. The first survey was conducted during April, 1991, and the second <br />during September, 1991. Both surveys involved visual observations for seeps and springs, <br />and resulted in no discovery of any additional spoil seeps or springs within the surveyed <br />area. <br />The field equipment used for sampling conductivity and temperature at the Nucla Mine (YSI <br />conductivity meter) was tested for accuracy on April 11, 1991. The Nucla conductivity <br />meter was calibrated by measuring the conductivity of a 1000 umhos /cm potassium chloride <br />(KCI) calibration standard solution at 4 degrees C. Based on the conductivity for this <br />solution at 4 degrees C (American Public Health Assoc., 1985, Pages 76 -80), the <br />conductivity of the solution should theoretically be 580 umhos /cm. The Nucla meter <br />registers a conductivity of 550 mhos /cm, or a 5.2 percent calibration error. A second <br />calibration was performed using a 1990 umhos /cm calibration standard and at 4 °C. The <br />Nucla meter registers a conductivity of 1100 umhos /cm against a theoretical conductivity <br />of 1154 umhos /cm, or a 4.7 percent calibration error. <br />The meter used to measure field - determined pH values at the Nucla Mine is calibrated by <br />performing two -point calibrations prior to each daily round of monitoring activities and <br />one -point calibrations prior to each measurement using buffer solutions of known pH values <br />obtained from outside laboratories. Three buffer solutions are used for calibration: 1) <br />pH 10; 2) pH 7 and 3) pH 4. The buffer solutions are replaced monthly to ensure accurate <br />calibration of the meter. Most of the two point calibrations are performed by using the <br />6 <br />