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4.0 Poor t'~ Unsuitable Material All overburden of poor to unsuitable quality has been identified in Appendix ii-4, Tables 5 through 13. 'IYre increments identified included lxx~r to unsuitable zones of clay, sodium, m3*+g~*+P~, nickel, zinc, lead„ cadmium, nitrate, pH, and acid-base potential. 4.1 Miticrat:ive Meastses All poor i:o unsuitable quality urrlerbimien will not be disturbed during mining. la.., includes many of the sodic aId acidic strata identified in Tables 4 arri 13. 'these zones will be mitigated by avoidance. All unsuitable zones (clay and sodium) associated with Core Hole 2614E will also be mitigated by avoidance. 'iY1e Wadge Coal seam is 1'll feet deep at this location and will not be mined. However, sodic overbunien may be enoamtered where the Ie~uwx coal seam is intercepted as the final highwall is reduced. Regrade3 spoil frc~ the Lerviox highwall reduction area (in the ~~j~ate vicinity of Drill Hole Site 2614E) will be sampled on a 300-foot grid and tested for sodium. Exposed sodic strata will either be buried in the final pit ar covered with two to three feet of suitable spoil. Many of the poor to unsuitable zones represent less than 15 percent of the overkx¢den core volume. 4Yrese zones will be mitigated by mix' This includes all unsuitable clay (except at Core 2034E), nickel, zinc, lead and cachnium zones, aryl many of the pH aryl acid-base potential zones. Manganese levels in the Wolf Creek area near Core Holes 2438E and 2334E will be monitored when the regraded spoil is sampled for pH and ABP levels. These zones will be mitigated by samplirw, chemical amendments aryl/or selective handling. Selective dragline hardlirrg techniques (mixing, segregating/burying acid strata, and/or segregating/topdressirg with suitable material) will be monitored by spoil sampling prior to soil redistribution to evaluate their effectiveness in eliminating unsuitable pH and ABP levels at C~ 6-153 Revised 12/10/92