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shown on Exhibit 6-6, Overburden Core Hole Location Map, to identify final graded areas having <br />unsuitable clay, pH, and acid base potential levels. Prior to topsoil replacement, final graded areas ' <br />will be sampled with a hydraulic soil sampler, backhoe, bucket auger, or other suitable equipment. One <br />representative sample from a vertical increment of 0.0 to 3.0 feet will be collected by or under the <br />supervision of a soil scientist from a 60 degree slant grid system with 500 foot centers. The soil <br />scientist will also inspect the surtace between grid points. If a significant change in root growth <br />medium characteristics is observed between grid points, additional sample points will be located. <br />Regraded spoil will also be visually inspected for compaction, possible root growth problems, and the <br />potential for slippage at the topsoil/spoil interface. <br />Shallow postmine soil pits will be excavated near revegetation monitoring sites to evaluate plant rooting <br />characteristics and compare topsoil/spoil data with site-specific revegetation data. Sample sites will <br />typically be placed in three-year-old revegetation areas at a frequency of about 1 site per 25 acres. Pits <br />will be excavated and topsoil and spoil will be sampled to a minimum depth of four feet. <br />At a minimum, final graded spoil samples will be analyzed for the following parameters to determine <br />suitability: pH, particle size, acid base potential, and saturation percent. The parameter list is based <br />upon the baseline information acquired during the premine overburden (Tab 61 and soil survey (Tab 91 <br />sampling programs. <br />The parameter list will be more closely evaluated once sufficient samples are collected to determine the <br />degree of sample variability. This approach will help to eliminate unnecessary and unwarrantable <br />analyses cost and data duplication. This parameter list represents those characteristics of the Seneca <br />II-W topsoil and overburden which may hinder plant growth on regraded spoil. Laboratory procedures <br />and suitability criteria will be identical to those tlescribed in Tab 6, Tables 6-2 and 6-13, and Tab 9, <br />Tables 9-1 and 9-2. <br />Unsuitable Spoil Mitigation Plan. If one or more parameters fall within the unsuitable range at a given <br />grid point, afour-part mitigation plan will be implemented. <br />The area around a suspect hole will be sampled on a closer spacing interval in order to better <br />define the lateral extent and variability of the unsuitable material. <br />4 Revised 4/24/91 <br />