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Introduction <br />The information assembled in this 2017 Annual Hydrology Report (AHR) <br />includes data collected from approved monitoring sites established at <br />Seneca Coal Company's (SCC) Yoast Mine (State Permit No. C-94-082). <br />Locations of monitoring sites discussed in this report can be found by <br />referring to Exhibit 7-1, Hydrology Monitoring Map, provided in the Yoast <br />Mine Permit Application Package (PAP). In addition, NPDES ponds and <br />surface water sites are depicted on Figures 1 and 2, Appendix A. A map of <br />ground water monitor wells is provided as Figure 3. <br />All references to 2017 (or to "this year") will be for Water Year 2017 <br />(October 1, 2016 through September 30, 2017) unless otherwise noted. All <br />tables referred to in the following text can be found in Appendix A. In <br />addition, a table of contents for Appendix A is given at the beginning of <br />that appendix. <br />The Yoast Mine permit went into effect on August 8, 1995. Overburden <br />removal began in October 1996 in the Grassy Creek basin and in 2000 in <br />the Sage Creek basin. The last of the coal at the Yoast Mine was removed <br />in February 2006. <br />Field conductivity and pH meters were calibrated prior to each day's use. <br />The conductivity meter is calibrated using a potassium chloride solution <br />with an electrical conductivity in the 1000 to 4000 umhos/cm range. The <br />pH meter is calibrated using NBS traceable buffers with pH values of 7 <br />and 10. Lab analyses have been performed by ACZ Laboratory in Steamboat <br />Springs, Colorado since May 31, 1983. ACZ Laboratory performs all analyses <br />by EPA or equivalent methods. Samples are delivered the day of collection <br />to the lab in an iced cooler. <br />SCC instituted in 1995 a new monitoring site numbering system for its new <br />ParadoxTM water quality database. This revised system is detailed in Table <br />A. For convenience sake, this table has been placed at the end of the <br />Table of Contents (see previous page). <br />1 <br />