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~~• VII. <br />~• <br />z <br />Alluvial Valley Floors -Rule; =~.:,~.8 and 4.24 <br />The Division is required to make specific ;,•ritten finding's on the existence of <br />and effects upon alluvial valley floors (AVF's) within the permit and adjacent <br />areas. A discussion of this investigation follows. <br />The applicant, in the coal load-out expansion volume, Exhibit D, describes one <br />area that can be considered an alluvial valley floor. This area is the valley <br />of Oak Creek within the permit area for the load-out which includes the first <br />and second terraces only. The Division has determined from this information <br />that Oak Creek meets the criteria for alluvial valley floors, as defined in <br />Rule 2.06.8(3). The area has (1) unconsolidated streamlaid deposits of over <br />30 feet in width and i0 acres in size associated with a stream, and (2) <br />sufficient water to support agricultural activities. <br />Map 2 of the load-out expansion volume delineates the extent of the Oak <br />Creek AVF. The map shows the width of the alluvial terrace being over 100 <br />feet on both sides of Oak Creek adjacent to the proposed load-out. Sufficient <br />water for irrigation was demonstrated for the Oak Creek AYF by the <br />identification of an irrigation diversion structure approximately one mile <br />upstream of the load-out. In addition, a ditch associated with the diversion <br />structure extends along the opposite side of Oak Creek to provide waters to <br />downstream agricultural fields. The topography of the load-out site is <br />varied, making the upper part of the site unsuitable far irrigation use. The <br />Division has determined that only the lower two terraces qualify as Alluvial <br />Valley Floors. Approximately 3 acres of the second terrace are generally <br />flat-lying, which would make them suitable for flood irrigation. The <br />vegetative species present on this lower area do not suggest that <br />subirrigation is occurring. This area is not currently used for flood <br />irrigation or subirrigation agricultura] activities, therefore, a <br />determination of the significance of this area on the farm's agricultural <br />production is not necessary. <br />The operation has been designed to minimize impacts to the Oak Creek A.Y.F. A <br />sedimentation pond has been constructed to protect the Oak Creek A.Y.F. from <br />additional sediment load. Also the coal loading pad has been designed to <br />prevent disturbance of the alluvial materials upon which the pad has been <br />constructed. Therefore, the proposed surface operations will not materially <br />damage the quantity or quality of water in surface and ground water systems <br />that supply the alluvial valley floor. <br />Dorchester Coal Company has proposed to regrade the area of the load-out to a <br />relatively flat surface and replace topsoil which was salvaged prior to <br />disturbing the area. In order to verify that the essential hydrologic <br />function of suitability of flood irrigation has been restored after mining, <br />the operator will need to monitor the infiltration and permeability <br />characteristics of the reclaimed area. The Division therefore imposes the <br />following stipulation: <br />• <br />