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these data are presented in Appendix Band statistically summarized <br />• in Table 18. A trilinear plot of the major ions is depicted in <br />Figure 12. <br />Because flow is visually estimated at this site, only seasonal <br />changes in flow can be qualitatively discussed. As one might <br />expect, the use of the Second Park Lateral irrigation ditch <br />directly affects the quantity of flow issuing from the coal and <br />overburden exposed along the highwall. Most of the flow <br />appears to be issuing along the contact between the overburden <br />and the upper Dakota Coal. During the winter when the <br />irrigation ditch is generally dry, there is little if any <br />visible flow along the highwall. During the summer, flow along <br />the highwall is continuous and, when the mine is in operation, <br />the pit must occasionally be pumped out to facilitate the <br />mining operation. Perusal of the data in Table 18 and Figure 12 <br />indicates that the quality of this water can be classified as a <br />Ca-S04 type. The relatively high percentage of 504 reflects the <br />• dramatic difference in quality from that of the proximate <br />undisturbed surface water system as monitored at SW-N7 on the upper <br />West Return Ditch. The mean TDS concentration for the period of <br />record is 1574 mg/1 ranging from 780 to 1912 mg/1. <br />Spoils Spring ~1 is located along the south-facing slope of a <br />west-east flowing reclaimed drainage which enters the <br />main stem of the West Return Ditch a few hundred feet upstream of <br />the NPDES 001 pond inlet as shown on Exhibit 7-8. This particular <br />spring was noted during a MLRD inspection on October 25, 1984 and <br />has been monitored since the fall of 1984 according to the same <br />program detailed in Appendix A for the Highwall Spring. Monitoring <br />of this spring to date (see Appendix 6, field remarks in <br />particular) has indicated that flow is perennial, reflecting the <br />same seasonal patterns previously described for the surface water <br />sites along the West P.eturn Ditch. Because this spring is in <br />essence a series of poorly defined seeps, it is impossible to more <br />accurately quantify flow than to simply qualitatively estimate the <br />changes in flow from month to month. <br />59 <br />