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• For Site 1, 7DS and sulfate values have been plotted on one graph, chlorides on a second <br />and manganese (total and dissolved) on a third (Appendix H). TDS and sulfates show a <br />slight increase with time (see previous paragraph). Chlorides and manganese show seasonal <br />variability but no discernible long-term trend. <br />NPDES Discharge Point 003. Hydrographs presented in Appendix E show that flow has <br />increased et this site since September 18, 1984, when operation of the truck wash <br />facilities began. Water is siphoned from the Yadge Impoundment (NPDES 002) into a holding <br />pond. Overflow from the holding pond is diverted into the shop ditch which flows into <br />NPDES 003. Water is pumped from the holding pond to the wash rack, drains into a settling <br />pond, and then into the same shop ditch. This operation has increased the flow at NPDES <br />003 while decreasing the flow et NPDES 002. Two other events that affected the long-term <br />hydrograph include the diversion away from NPDES 003 of runoff from a fly ash pit operated <br />by Colorado-Ute Electric Association in October, 1980, end the diversion away from NPDES <br />003 of runoff contained in the Northwest Diversion Ditch (see the Seneca 11 Permit <br />Application, Exhibit 7-7, Surface Water Hydrology Map and also the 1982 Seneca II AHR) in <br />April, 1982. Finally, discharge volumes et the 003 site have been affected by the <br />• reduction in diameter of the discharge culvert (36 inches to b inches) which occurred on <br />July 19, 1988. No comparison of this years' flows to prior years is presented since the <br />operation of the truck wash system tends to greatly influence the flow conditions et Pond <br />003. <br />Review of Table 15 (Appendix A) shows a dramatic shift in water quality after 1984, Prior <br />to the truck wash operation, the average annual TDS of the flows at NPDES 003 ranged from <br />1,225 to 1,578 mg/l. After the truck wash operation, the TDS range increased to 2,491 to <br />3,028 mg/l, The water remains generally a MgC a-S04 type, although the percentage of <br />sulfates have increased approximately 14 percent, and bicarbonates have decreased since <br />the beginning of the truck wash operation. This water is of similar quality to that found <br />et NPDES 002. <br />For NPDES 003, TDS and sulfate values have been plotted on one graph, manganese {total end <br />dissolved), sulfides and zinc on a second end ammonia on a third (Appendix H). Review of <br />the TDS/sulfate graph reinforces the data discussed in the previous paragraph. The <br />manganese plot exhibits seasonal variability with no distinct long-term trend. Sulfide <br />• show a possible decrease el th ough this observation may be biased by improved lab technique <br />(i.e., decreased detection limit). Zinc values show a slight increase. Ammonia <br />19 <br />