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shown on Exhibit 6-6, Overburden Core Hole Location Map, to identity final graded areas • <br />having unsuitable clay, pH, and acid base potential levels. Prior to topsoil ~~ <br />replacement, final graded areas will be sampled with a hydraulic soil sampler, backhoe, <br />bucket auger, or other suitable equipment. One representative sample from a vertical <br />increment of 0.0 to 3.0 feet will be collected by or under the supervision of a soil <br />scientist from a 60 degree slant grid system with 500 foot centers. The soil scientist <br />will also inspect the surface between grid points. If a significant change in root growth <br />medium characteristics is observed between grid points, additional sample points will be <br />located. Regraded spoil will also be visually inspected for compaction, possible root <br />growth problems, end the potential for slippage et the topsoil/spoil interface. <br />Shallow postmine soil pits will be excavated near revegetation monitoring sites to <br />evaluate plant rooting characteristics and compare topsoil/spoil data with site-specific <br />revegetation data. Sample sites will typically be placed in three-year-old revegetation <br />areas at a frequency of about 1 site per 25 acres. Pits will be excavated and topsoil and <br />spoil will be sampled to a minimum depth of four feet. <br />Rt a minimum, final graded spoil samples will be analyzed for the following parameters to • <br />determine suitability; pH, particle size, acid base potential, end saturation percent. <br />The parameter list is based upon the baseline information acquired during the premine <br />overburden (Tab 6) end soil survey (Tab 9) sampling programs. <br />The parameter list will be more elosely eve Luated once sufficient samples ere collected to <br />determine the degree of sample variability. This approach Mill help to eliminate <br />unnecessary end unwarrantable analyses cost end date duplication. This parameter list <br />represents those characteriatita of the Seneca II-W topsoil and overburden which may <br />hinder plant growth on regraded spoil. Laboratory procedures and suitability criteria <br />will be identical to [hose described in Tab 6, Tables 6-2 and 6-13, and Tab 9, Tables 9-1 <br />and 4-2. <br />Unsuitable Sooil Mitigation Plan. If one or more parameters fall within the unsuitable <br />range at a given grid point, a four-part mitigation plan will be implemented. <br />1. The area around a suspect hole will he sampled on a closer spacing interval in order <br />to better define the lateral extent and variability of the unsuitable materiel. <br />4 Revised 04/24/91 • <br />