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<br />(3) 'f.he rocl: subdrain must be installed as detailed within the report. <br />The durable rock drain is to he a minimum of 4 feet tliick',ahd 10 feet wide <br />and is to slope at least 2% axially, in order to facilitate drainage. <br />The rock drain should be arcapped in a filter fabric (TYPAR type 3401 <br />was specified within the consultant's report). <br />x NOTE: <br />'Che consultant's report does not address whether or not the subdrain has <br />been installed as originally designed beneath the e:<isting portion of <br />the coal processing waste pile at the Dorchester No. 1. The report <br />only concludes that such a drain will have to exist for the final pile <br />to be sufficiently stable. <br />(4) The refuse material should be placed in horizontal lifts not to <br />exceed 3 feet in uncompacted thickness and then properly compacted as <br />described above. <br />(5) Runoff from adjacent slopes must be diverted above the waste pile in <br />order to prevent runoff from saturating the processing waste. In addition, <br />the final top surface of the waste pile must be graded to no less than a <br />O. Si slope, in order to Facilitate drainage of precipitation from the pile. <br />(6) No impoundments of water' should be allowed.to occur on the waste pile. <br />Several deficiencies remain to be resolved prior to approval of the plan f.or <br />reconstruction. No discussion or consideration of the consequences of <br />subsidence of underground mine workings beneath the pile was contained within <br />the consultants report. Geotesting laboratories, Inc., in a report <br />prepared in January of 1981, observed that the maximum 30 feet Fill height, <br />which was proposed aC that time, would not significant].}' effect subsidence <br />occurrance. In light of the proposed increase to a maximum thickness of <br />75 Eeet of processing waste,the consultant should address the projected <br />consequences of the construction of a larger coal processing waste pile on <br />the site. Differential settlement, if it were to occur, might disrupt the <br />subdrains or tender the surface drainage facilities ineffectual. As the <br />consultant observes, if the subdrain were to fail the result would be <br />detrimental to the pile's stability. <br />Secondly, the report does not address the indirect consequences of the <br />proposed pile construction. The exisCing topsoil stockpiles will be <br />displaced by the pile's f.i.nal configuration. Phasing of the pile <br />construction is not proposed within the report. The operator should <br />describe how the need for topsoil stockpile capacity will be resolved <br />with thcp].annod~uonr..truction oP.tho cond. proccasinr wnsto pile. <br /> <br />