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<br />SWELL FACTOR STUDY <br />Johns to Johnson <br />January 30, 1984, Page 2 <br />Upon examining the location of area A-2 in Ashmore Pit, it becomes obvious <br />why this area produced such a low factor (7.9Y.). As can be seen on the plan map <br />(Exhibit 1), the northern ends of these pits receded to the south as Ashmore Pit <br />moved eastward across a ridge top and the overburden deepened. <br />When this happened, spoiling room was increased at the north ends of the <br />pits as each successive cut shortened and the spoil was cast into the preceding <br />longer cut. This 'final cut phenomena' at the north ends, where overburden is <br />deepest and swell would normally produce Its greatest effect, resulted in a <br />lowered regrade profile. In examining Exhibit 3 (profiles 1-20) this situation <br />is clearly illustrated by comparing profiles 6-10 of the A-2 area with those of <br />the other pit areas. (Ashmore A-1 --- I-5, Derringer --- I1-16, and Enfield --- <br />17-20) <br />As Ashmore Pit moved eastward beyond the A-2 study area, approaching the <br />next drainage and shallowing overburden, the cuts again lengthened to the north. <br />Here the opposite scenario is encountered where box cutting is required and <br />spoiling room is decreased, resulting in a higher regrade profile. This is <br />verified upon examination of the postmining contour map. A larger A-2 study <br />area encompassing more cuts to the east would more than likely have produced an <br />average swell factor similar to the other three study locations. <br />In summary, I believe this study has verified, most clearly, our assumed <br />25Y, overburden swell factor. Although some profiles varied markedly from <br />others, representing site specific operational and regrading procedures, drain- <br />age requirements, overburden depths, etc., it appears that a number of profiles <br />or cross sections over a large area will give reliable results. Each pit area <br />produced a swell factor equal to the overall mine average. An oversight in lay- <br />ing out the A-2 study area, as explained above, resulted in the only discrep- <br />ancy. In conclusion, I feel our assumed 25% swell factor can now be considered <br />actual. <br />LJ/js <br />