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recorded for sites WC-138, WC-157, and WC-158. Spoil mixing by standard dragline and dozer <br />techniques at these shallow overburden sites has not been sufficient to blend and dilute or <br />bury unsuitable acidic overburden strata. <br />The Wolf Creek spoil generally contained about 40 to 60 percent (by volume) slightly hard <br />sandy shale and moderately hart fine-grained siltstone and sandstone rock fragments. the <br />selectively placed subsoil topdressing generally contained about 30 [0 40 percent (by <br />volume) moderately hard fine-grained sandstone rock fragments. These rock fragments are <br />beneficial for root growth, water and air movement, water and nutrient availability, and <br />overall minesoil productivity (Ashby et al ., 1984)- <br />A compaction evaluation was completed for the upper four feet of spoil in each backhoe pit. <br />Non-compact loose spoil was identified at 23 (80 percent) of the sample sites. Slightly <br />compact spoil occurred beneath the subsoil-spoil interface at sites WC-136, W[-137, WC-138, <br />WC-153, WC-154, and WC-156. Root penetration will not be restricted significantly by the <br />slight degree of compaction. <br />In summary, suitable levels of EC occurred in the upper four feet of spoil at every backhoe <br />• pit site. Suitable levels of pN and ABP were identified wherever a spoil topdressing of <br />subsoil has been replaced or where deeper overburden was encountered and sufficient spoil <br />mixing occurred prior [o final grading. Sites WC-138, WC-157, and WC-158, all lot ated in <br />shallow overburden areas (cropline or drainage) had an unsuitable ABP value. An additional <br />one to three feet of suitable topdressing will be spread in the vicinity of these three <br />sites to adequately bury the acid spoil. one site, WC-135, had a soil reaction value of <br />3.9; however, normal root growth was evident to a depth of 2.5 feet. Additional cover soil <br />will not be required at this site. The topdressing medium has suitable chemical and <br />physical properties. All suitable spoil topdressing replacement areas for the 1991 field <br />season are shown on Exhibit 91.2. <br />Quality Control and Duplicate Samples, duality control is an important part of the Seneca <br />II Mine soil and spoil monitoring program. One aspect of this quality control program is <br />to have the primary laboratory facility complete duplicate analyses on 5 [0 10 percent of <br />the total samples and on field-split blind samples. The duplicate analyses, presented on <br />the enclosed laboratory reports in Attachments 91.1 and 91.2 were very comparable with the <br />original samples. <br />8 <br />