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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. Finally, a smaller volume pump and line <br />from Pond 002 to the truck wash was installed in August 2001. <br />This year's average flow value, 0.072 cfs, is 50% below the historic <br />(1980-2009) average flow value, 0.145 cfs. However, the operation of <br />the truck wash system, and the timing of flow measurements, tends to <br />greatly influence the flow values reported. The truck wash was last <br />used in 2007. Review of the TDS plot (SF = 0.5) indicates a decreasing <br />trend, with the peak value occurring in September 2002. <br />- Surface Water Site SW-S2-3 (SSG3). This site monitors discharges from <br />pre-SMCRA mining areas before they enter Grassy Creek at a point just <br />below Site SW-S2-2. Monitoring at this site was re-established in June <br />1997. This site often dries up in late summer, but was flowing from <br />April through September this year. Review of the TDS plot indicates a <br />decreasing trend. <br />- Surface Water Site SW-S2-2 (SSG2). This site is the furthest <br />downstream surface water site in the Little Grassy and Grassy Creek <br />drainages prior to exiting the permit area. Therefore, it is the most <br />significant monitoring site with respect to showing the cumulative <br />effects of mining in this area. Review of the TDS plot indicates an <br />increasing trend. <br />On page 7-242 of the Seneca II PHC, predictions of TDS values at this <br />site were made. A value of 1233 mg/l was predicted in June, while a <br />value of 2380 mg/1 was observed. A value of 2341 mg/l was predicted in <br />September, while a value of 3730 mg/l was observed. It should be noted <br />16 t