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required. The results of the subsidence to roads will, <br />therefore, be no more than a temporary inconvenience and will not <br />result in any kind of lasting impact. <br />2.6.3 ggfuse Disgosal Area <br />The refuse disposal area is underlain primarily by the main <br />access entries, however, some portions of the refuse area is <br />Underlain by sub-mains (see Mine Plan Map in Appendix A). <br />The mining under the main access entries, as discussed, will <br />be accomplished in two phases. The first phase, which has been <br />completed, in many areas consists of development mining. No <br />evidence of subsidence has been observed by Dorchester in areas <br />where the development phase of mining has been completed. The <br />second phase consists of pillar extraction or retreat mining <br />which will approximate extraction conditions of long-wall mining. <br />• This phase is expected to experience subsidence, the impacts of <br />which are discussed below. <br />The impacts to the refuse pile are expected to be, for the <br />most part, minimal. The worst condition for the main entry <br />extraction that could occur would be differential settlement over <br />the length of the rock drain caused by the retreating face. The <br />differential settlement would be gradual and will allow <br />communication along the rock drain to continue. The condition <br />could produce accumulation of the water within the interior of <br />the refuse pile up to the level of the subsidence (maximum 5.7 <br />feet, as shown in Table 1.0). Once the seepage reaches this <br />level, the water will then be carried through and away from the <br />refuse area within the drain. Since this accumulation would <br />occur in the interior portion of the pile, the piezometric <br />19 <br />