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NININfi PLAN <br />seam on the south end of the site appears to also be underlain by shale. It <br />• appears there must have been an erosion cycle after the higher elevation <br />gravel was deposited and before the lower elevation gravel was laid down. <br />Faulting could also account for this pattern, but no evidence of faults is <br />present. If there was an erosion cycle then sore variations in the thickness <br />and extent of the lower elevatim gravel would be expected. That gravel may <br />have been laid on tap of an eroded shale surface that was partially dissected <br />by tributary streams and drainages that existed prior to the depositional <br />cycle that produced the lower elevation gravel seam. There is no way to <br />definitely determine whether this variation actually exists until the gravel <br />is removed. <br />The overburden consists of soil and subsoil. In most areas the soil <br />developed from the gravel deposit itself. But in the west central portion of <br />the site Csee Exhibit C1) a moderately deep Stoneham loam soil exists to a <br />maximum depth of about 4 to 5 feet on tap of the gravel layer. Thus all <br />overburden is soil or soil like material and no bedrock of any kind exists on <br />tap of the gravel deposit. Figure 1 shows cross-section A-A' through the site <br />with a 33:1 vertical exaggeration. <br />DI.RATIQV ~ (1PERATIOIV: This operation will last a considerable amount of <br />time. Although the gravel is only about 10 feet thick, the size of the area <br />to be mined contains a large volume. Current projections are that average <br />annual production will be about 250,000 tons. However, because gravel mining <br />is totally dependent upon activity in many other industries, all of which have <br />their variations from year to year, stating an average annual tannage is <br />somewhat misleading. <br />Past experience has shown that in one year demand can be almost zero and <br />the next year production can swell to a million tans and the third year can <br />once again see virtually no demand. Therefore, the statement of an average <br />annual tannage of 250,000 tans is not intended to be a corm~itment that this <br />amount will be produced every year or that this amount is the maximum amount <br />that will be produced in any one year. The production rate and therefore the <br />life of this operation is totally dependent upon demand. However, based upon <br />this speculative, long term, average annual productim rate, the life of the <br />mine would be around 30 years. <br />• <br />Page 4 <br />