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Unsuitable materiel was identified in the overburden et ten of eleven sample locet~ions •
<br />within the proposed disturbance area (Tab b, Exhibit 6-4). The unsuitable parameters, pH,
<br />saturation percentage, particle site, boron, molybdenum, acid-base potential, manganese,
<br />zinc, and iron comprise 1.1 to 41..8 percent of the overburden section (Tab 6, Appendix
<br />b-3) et the sample sites. Only one sample had an unsuitable sodium adsorption ratio; the
<br />Madge interburden at Site 2309E. these parameters ere discussed in greater detail in the
<br />following section.
<br />Acid- and Toxic-Forming Materiels. Acid- and toxic-forming materials were identified) it
<br />the Yoest study area es discussed in Tab 6 and listed in Tab 6, Appendices 6-2 and i5-3.
<br />Appropriate mitigation measures such as avoidance, extraction by mining, laboratory error,
<br />ameliorating reclamation techniques, sample contamination, selective handling, or
<br />blending, dilution, end/or burial by normal overburden handling, will be used to replace a
<br />suitable four-foot root growth medium, including soil, and to prevent leachetes end rwioff
<br />from entering the ground water system or di st harping into the surface water system. No
<br />roads will be surfaced with acid-forming materi alc.
<br />Mitigation of all unsuitable zones within the underburden materiel (19 percent of all 106 •
<br />unsuitable zones which were identified) will be by avoidance, i.e., these zones will not
<br />be disturbed by mining activities. Certain areas of overburden (Sites 2310E, 2311E, and
<br />2312E) will also be avoided due to the projected disturbance area boundary described
<br />within this PAP (Tab 6, Exhibit 6-4) or excessive Wedge coal seam depths. These
<br />additional avoided areas comprise 33 pereent of all 106 unsuitable zones which were
<br />identified. Wedge and Wolf Creek coal seem unsuitable zones Ceight percent) will be
<br />mitigated by extraction. The unsuitable pH, sodium adsorption ratio, molybdenum, sand,
<br />iron, zinc, manganese, boron, 50 percent of the acid-base potential, end 22 percent of the
<br />clay zones (30 percent of ell 106 unsuitable zones) will be mi tigeted by overburden
<br />blending, dilution, and/or burial by normal overburden handling techniques. All of these
<br />zones comprise 16 percent or less of the overburden section (Tab 6, Appendix 6~4).
<br />According to Dollhopf et al. (1978), overburden zones of unsuitable quality materiel will,
<br />with mathematical reasoning, be acceptable materiel for reclamation by the spoil mixing
<br />ph enomene. The degree of mixing can be ascertained by comparing the emouni of unsuitable
<br />overburden to the amount present in the resultant spoils. These results generally showed
<br />that when critical parameter percentages comprise 0 is 15 percent of the overburden cure,
<br />the parameter is blended end completely diluted during the course of mining. Therefore,
<br />based on [he above discussion, about 90 percent of ell unsuitable zones will be mitigated
<br />by avoidance, extraction, end mixing.
<br />2 Revised 03/01/95
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