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State Reg. <br />material for reclamation by the dilution phenomena. The inimical <br />composition of each core is determined and compared to the mixing <br />phenomena developed by Dollhopf et al., 1978. Lastly, other mitigation <br />measures are discussed where necessary. <br />Statistical Variability <br />Summary statistics for physiochemical analysis of overburden and <br />underburden are presented in Tables 6-4 and 6-5. This data includes <br />range (maximum and minimum), mean standard deviation, and sample <br />frequency. The majority of mean values plus one standard deviation all <br />fall within an acceptable range as outlined by the overburden assessment <br />criterion listed in Table 6-3. Exceptions include the acid-base potential <br />for both overburden and underburden and the sodium adsorption ratio for <br />underburden. The overburden and underburden variability is generally <br />quite low. However, significantly high variability was evident among the <br />• following parameters and can be attributed to the following factors. The <br />sand, silt, and boron variability of underburden exceeded that for <br />overburden because several coal stringers were identified in the <br />underburden. Coal strata often cause extremely high sand percentages <br />due to its particle density. The sodium concentration and sodium <br />adsorption ratios of the underburden were extremely variable ranging <br />from 0.4 to 22.7. This is caused by a highly sodic strata existing in select <br />region of the permit area, namely near Cores 1900 and 2306 (also see <br />Groundwater Chemistry Section, Tab 7). Concentrations of calcium, <br />magnesium, and acid-base potential were more variable in the <br />overburden than underburden. This is due to difference between <br />calcareous sandstones and carbonaceous shales directly above coal <br />seams. Larger manganese, nickel, and zinc variances in overburden is <br />probably due to drilling greases and/or uneven drill bit wear. Iron is <br />highly varible in both overburden. and underburden and is due to <br />differences in strata and possibly uneven bit wear. <br />• In general, sandstone and shale overburden associated with the Wolf <br />Creek coal beds have' higher conductivities, more acidic pH levels, and <br />lower acid-base potentials than Wadge coal overburden. The Wadge coal <br />6-25 <br />