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• suitable levels for site 873E and therefore were not determined on <br />samples collected from sites 874E, 875E and 816E. <br />The following parameters occasionally exceeded suitability levels and <br />showed considerable variability across most lithologic units. <br />Saturation percentage values ranged from 27 to 110 percent and, except <br />for Unit 2 (upper Dakota Coal seam and surrounding very dark gray <br />carbonaceous shale), were suitable for all lithologic units. The mean <br />saturation percentage of 72 percent recorded for Unit 2 was <br />significantly higher than all other lithole9ic units (Table 6-15). <br />Salinity values were all suitable ranging from 0.6 to 8.3 minhos/cm. <br />Salinity values were slightly higher in Unit 2. Active acidity (pH) <br />values ranged from 3.5 to 7.8. As shown in Table 6-10, the reaction <br />values are neutral (7.2) for Unit 1, strongly acid (5.5) for Unit 3 and <br />extremely acid (4.0, 3.9 and 4.3) for Units 2, 4 and 5. Similar <br />potential acidity values were recorded for acid base potential (ABP). <br />• TFie ABP values ranged from an excess of 192 to a deficiency of 40 tuns <br />of calcium carbonate per acre furrow slice. ABP values were highast in <br />the overburden (Unit 1) and lowest in the upper Dakota Coal seam (Unit <br />2). t4ean ABP values were unsuitable for Units 2 (-11.9) and 4 (-5.6). <br />Except for one underburden sample from site 873E, all manganese <br />concentrations were suitable ranging from 0.1 to 14.3 ppm. These <br />manganese levels are considered to be typical and adequate for normal <br />plant growth (Barth et al., 1981). The underburden sample which had an <br />unsuitable manganese concentration of 103 ppni, will not be disturbed by <br />mining. Extractable iron concentrations were highly variable ranging <br />from 1 to 636 ppm. Excessive levels (i.e. 300 ppm) were associated with <br />the upper Dakota Coal seam (Unit ~), lower inderburden shale (Unit 4) <br />and the underburden (Unit 5). Although these levels niay not necessarily <br />be toxic, they may be high enough to cause appreciable nutrient <br />imbalances (Barth, et al., 1981). <br />. Mitigative Measures for Unsuitable Material. Zones of. unsuitable <br />material were identified at each of the four Phase II sample locations <br />and are documented by parameter, lithologic unit, location and sample <br />6-52 Revised 3/6/81 <br />