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Station #E20 is on Coal Creek, downstream from the outfall from the sediment retention ponds, the <br /> so-called 001 discharge. Data from all other stations will be discussed in general terms. <br /> For the parameters TDS, TSS, and conductivity, there are no apparent differences between the data <br /> presented earlier (Posey, 1993) and this study. These parameters will be covered only in the context <br /> of their relations to those discussed in the present report. <br /> OBSERVATIONS <br /> General _ <br /> All of the data discussed in this report are given in the accompanying table. These were collected <br /> from the Annual Hydrology Reports provided by Mid-Continent Inc. and from a few discrete <br /> sampling events conducted by the Division of Minerals and Geology or others. <br /> The concentrations of several parameters vary consistently with time of year and usually are higher <br /> in winter than in spring months. Also, several components of the data set have an obvious shift in <br /> concentrations beginning in 1987. Possible causes for the shifts are discussed in Posey (1993). <br /> Seasonal Variations in Alkalinity, TDS and Conductivity <br /> Alkalinity, TDS and Conductivity report strong seasonal variations; these parameters are elevated <br /> in the winter (low flow) months relative to spring. Elements that control this characteristic, at least <br /> in part, include Na, Mg, Cl, and to a smaller extent, Fe. Also, the concentrations are also affected <br /> by the dilution effects of snowmelt during March through June. <br /> pH <br /> Between 1976 and 1986, pH varied generally between about 7.6 and 8.5. Afterwards, the median <br /> value shifted to about 8.6 within a range of 8.4 to 8.8. <br /> The overall shift in pH accompanied the decrease in TSS, and the increases in Alkalinity, TDS and <br /> Conductivity. However, the seasonal variations shown for TSS, TDS and Conductivity vary <br /> independently of pH. Thus,the pH variations are related to activities at the site in a manner similar <br /> to the other parameters, but pH is affected by other or additional components. <br /> Na and SAR <br /> Sodium concentrations demonstrate a strong seasonal control, with higher measures in winter than <br /> in spring. The sources of sodium in this area are not well known to me, but the geochemical <br /> information indicate several possible minerals including Na-clays or some Na-sulfate mineral. <br /> The sodium adsorption ratio follows mostly the trends of sodium concentration,and the relationship <br /> is linear. <br /> Both Na and SAR increased, on average, in 1987. However, the lower range remained essentially <br /> the same. The discharge of higher Na contents beginning in 1987 and the characteristic increase in <br /> 2 <br />