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SSG1, NPDES Discharge Point 003, (also known as the Shop Reservoir or <br />the Northwest Impoundment, located just north of the mine shop area), <br />SSG2 (located approximately 0.1 mile downstream of where NPDES3 <br />discharges into Grassy Creek) and, finally, YSG5 (the furthest <br />downstream site). <br />- Surface Water Site YSGF5. This site was initially part of the <br />monitoring program for Seneca Coal Company's Yoast Mine, and is now also <br />part of the PSCM program. It is in the upper part of Grassy Creek, just <br />below the confluence of the Yoast NPDES Pond 011 discharges. Review of <br />the TDS plot indicates a slightly increasing trend, with the peak value <br />occurring in September 2010. <br />- Surface Water Site SW-S2-1 (SSG1). This site monitors Grassy Creek <br />upstream of mining at the Seneca II Mine. Review of the TDS plot <br />indicates a stable trend (SF 0.5). <br />- NPDES Discharge Point 003 (NPDES3). Hydrographs presented in Appendix <br />D show that flow has increased at this site since September 18, 1984, <br />when operation of the truck wash system began. Water is siphoned from <br />the Wedge Impoundment (NPDES2) into a holding pond. Overflow from the <br />holding pond is diverted into the shop ditch, which flows into NPDES3. <br />Water is pumped from the holding pond to the wash rack, drains into a <br />settling pond, and then into the same shop ditch. This operation has <br />increased the flow at NPDES3 while decreasing the flow at NPDES2. <br />Other events have affected the long -term hydrograph at NPDES3. They <br />include the diversion away from NPDES3 of the runoff from an inactive <br />fly ash pit (operated by the Hayden Station power plant) in October 1980 <br />and the diversion away from NPDES3 of runoff contained in the Northwest <br />Diversion Ditch (see the Seneca II Permit Application, Exhibit 7 -7, <br />Surface Water Hydrology Map and also the 1982 Seneca II AHR) in April <br />1982. Discharge volumes at the this site have also been affected by the <br />reduction in diameter of the discharge culvert (36 inches to 6 inches) <br />that occurred on July 19, 1988. A smaller volume pump and line from Pond <br />002 to the truck wash was installed in August 2001. The truck wash was <br />13 <br />