Laserfiche WebLink
Other events have affected the long-term hydrograph at NPDES 003. They <br />include the diversion away from NPDES 003 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 NPDES 003 of runoff contained in the <br />Northwest Diversion Ditch (see the Seneca II Permit Application, Exhibit <br />7-7, Surface Water Hydrology Map and also the 1982 Seneca II AHR) in <br />April 1982. Discharge volumes at the 003 site have also been affected by <br />the reduction in diameter of the discharge culvert (36 inches to 6 <br />inches) that occurred on July 19, 1988. Finally, a smaller volume pump <br />and line from 002 to the truck wash was installed in August 2001. <br />This year's average flow value, 0.068 cfs, is 45R of the historic (1980- <br />2005) average flow value, 0.151 cfs. However, the operation o£ the <br />truck wash system, and the timing of flow measurements, tends to greatly <br />influence the flow values reported. Review of the TDS plot indicates an <br />increasing trend. <br />- Surface Water Site SW-52-3 (SSG3). This site monitors discharges from • <br />pre-SMCRA mining areas before they enter Grassy Creek at a point just <br />below Site SW-52-2. This site was re-established in June 1997. Not <br />enough data has been collected yet to detect any trends. It was dry in <br />June through September the past five years. <br />- Surface Water Site SW-52-2 (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/1 was predicted in June, while a <br />value of 2270 mg/1 was observed. A value of 2341 mg/1 was predicted in <br />September, while a value of 3100 mg/1 was observed. It should be noted • <br />that the PHC predictions were based on long-term average values. <br />18 <br />