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only the furthest downslope highwall portions of the spoil exhibit <br />significant amounts of saturation. <br />Ground Water Quality. Ground water samples were collected from sixteen <br />wells on an annual or biannual basis. The parameter list used for all <br />wells sampled this year is given on Table 4. Analyses have been <br />performed by ACZ Laboratory in Steamboat Springs, Colorado since May 31, <br />1983. ACZ Laboratory performs all analyses by EPA or equivalent methods. <br />Samples are delivered the day of collection to the lab in an iced <br />cooler. A complete description of the ground water monitoring program <br />may be found on pages 7-336 to 7-355 of the Seneca II PAP, and is <br />summarized on pages 7-341/342. <br />The following discussion of the analytical data collected during the <br />reporting period is arranged by strata being monitored and coincides <br />with the format (by aquifer type) in which the analytical data are <br />presented in Appendix C. The discussion of water quality will be <br />limited to a description of total dissolved solids (TDS) concentrations. • <br />A separate section, Comparison of Ground Water Quality to Water Use <br />Standards, will discuss any samples that exceed water use standards. <br />Data for each well in this appendix begins with a listing of the water <br />quality data collected during the past three years, followed by remarks <br />explaining the sampling procedure. This is followed by a plot of TDS <br />versus time for the entire period of record. The regression line on <br />this plot is generated by a method known as LOWESS (LOcally WEighted <br />Scatterplot Smoothing). Unless otherwise noted, a smoothness factor <br />(SF) of 1.0 (on a scale of 0 to 1) was used, which results in maximum <br />"smoothing". Finally, this plot is followed by a table listing historic <br />TDS values and percent milliequivalents for major ions. <br />- Alluvium. Two wells are sampled in the Grassy Creek alluvium. Well <br />71 monitors the alluvium upstream of mining at Seneca II. It displays <br />an increasing TDS trend. Well 70 monitors the alluvium below Seneca II <br />and also downstream of the confluence with Scotchmans Gulch. It <br />displays an increasing TDS trend. <br />4