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The following discussion of the analytical data collected during the reporting period is <br />arranged by strata being monitored and coincides with the format (hy aquifer type) in <br />which the analytical data are presented in Appendix C. The discussion of water quality <br />will be li.mi ted to a description of total dissolved solids (TDS) concentrations. A <br />separate section, Comparison of Ground Watet Quality to Water Use Standards, will dascuss <br />any samples that exceed water use standards. <br />Data for each well in this appendix begins with a listing of the water quality data <br />collected during this year, followed by remarks explaining the sampling procedure. This <br />is followed by a plot of TDS versus time for the entire period of record. The regression <br />lino on this plot is generated by a method known as LOWESS (LOCally WEighted Scatterplot <br />Smoothing). A smoothness factor of 1.0 (on a scale of 0 to 1) was used, which results in <br />maximum "smoothing". Finally, this plot is followed by a table listing historic TDS <br />values and percent milliequivalents for major ions. <br />Alluvium. Well 32 is located furthest upstream on Little Creasy Creek. Review of the TDS <br />plot indicates-an increasing trend. This is due to the contribution of waters from Spoil <br />Springs 3, 4, and 5. Further downstream, Well' 6 also displays an increasing TDS trend for <br />similar reasons. Furthest downstream on Little Grassy Creek and belor NPDES 002, ie Well ~ • <br />31A. It also displays an increasing TDS trend. <br />Three wells are sampled in the Grassy Creek alluvium. Well 71 monitors the alluvium <br />upstream of mining at Seneca II. It displays an increasing TDS trend. Well 33 monitors <br />the Grassy Cteek alluvium at the Little Creasy Creek confluence. It displays an <br />increasing TDS trend. well 70 monitors the alluvium below Seneca II and also downstream <br />of the confluence with Scotchmana Gulch. It interestingly displays a slightly decreasing <br />TDS trend. <br />In the Cow Camp Creek alluvium (below NPDES 004), water quality is measured at two wells. <br />Well 46 displayed an increasing TDS trend until 1956/1987, then a decrease until 1991, and <br />finally an increase since 1991. The reason for this TDS "dip^ is unknown, Well 69, <br />located below 46, interestingly displays a decreasing TDS plot. <br />Well 68, completed in the Bond Creek alluvium (below NFDES 008), was drilled along with <br />Well 69 (see above) rn 1988. It likewise displays a decreasing TDS plot recently. <br />• <br />6 <br />