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site SW-N1. However. because there is no water quality data • <br />predating mining activities, it is impossible to know what <br />premising baseline conditions were. The quality oi' the water <br />at site Sk'-N3 can be classified as. a Ca-Mg-S(i4 type as <br />indicated from Figure 2. From Figure 5, the ef•Fects of mining are <br />clear. As depicted by the stiff diagrams, the estimated quality of <br />the Second Park irrigation water (estimated from samples collected <br />in 1986 from the West Lateral irrigation dit~:h) changes <br />substantially in TDS load and water type as the irrigation return <br />water flows through the mine area. As the Ca-H~~03 type irrigation <br />water infiltrates into the undisturbed and disturbed (by mining) <br />near surface ground water system, water type sharply changes to a <br />Ca-S04 type as indicated by the stiff diagrams for the Highwall <br />Spring and the Spoils Spring ill, respectively. These waters <br />strongly influence the type of water discharging from the mine area <br />as reflected by the similarity of these waters to the water <br />discharging from the NPDES 001 discharge point located immediately- <br />upstream of SW-N3. As a result of the above-described process, TDS • <br />concentrations also increase approximately two times that of <br />background concentration (observed at site SW-N7) as surface water <br />flows through the mine area and is fed by spoils. grounA water. The <br />resultant impact of the quality of the West Return Ditch on the <br />quality of Tuttle Draw is reflected by the similarity in TDS <br />concentration of SW-N3 to that of NPDES DO1. <br />As was similarly described for site SW-N1, water quality data <br />collected at site SW'-N3 reflect dramatic seasonal changes in <br />quality with respect to TDS. As is evident from the chemograph <br />depicted on Figure 6, 7DS concentration averages 2139 mg/1 and <br />fluctuates between a low of approximately 1000 mg/1 during the <br />summer and a high of approximately 3300 mg/1 during the winter. <br />This flux is directly related to irrigation return flow. Figure 7 <br />is a plot of TDS concentration versus flow ai; SW-N3; the direct <br />relationship of increasing TDS concentration with decreasing flow <br />is apparent. • <br />26 <br />