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-32- <br />A discussion of the drainage and sediment control system, as well as detailed <br />designs, can be found in Volume II, Section 2.05, page 174-175; Response <br />Volume I, Section 2.05.3(3), and 2.05.3(4); and REsponse Volume II, Attachment <br />A, page 1-15, and Appendix A, B, C, D, E. <br />The operation utilizes upland diversion ditches that divert undisturbed <br />drainage away from the active, disturbed mine areas. This practice reduces <br />the volume of water that comes in contact with disturbed areas and, therefore, <br />reduces the amount of water needing treatment prior to discharge. <br />Runoff from disturbed areas, such as the coal waste pile, is routed to <br />sedimentation ponds through the use of collection ditches. These <br />sedimentation ponds reduce the levels of settleable and suspended solids to <br />levels that meet State and Federal discharge standards. After treatment, the <br />water is discharged back to the natural stream course downstream of the <br />disturbed areas. <br />Water from underground mine inflows and coal preparation plant operations is <br />also treated in tanks and temporary impoundments prior to reuse or discharge. <br />If the chemical quality of mine water becomes unacceptable, a chemical <br />treatment system (utilizing sodium hydroxide and flocculents) is available to <br />treat the water prior to discharge. <br />Three small areas of the mine that are disturbed are not treated by the mine <br />sediment control system. The operator has requested a small area exemption <br />from these areas based on the rationale that these areas are so small or of <br />such a condition that treatment of runoff is not needed. The areas include 1) <br />the roadside topsoil stockpile, 2) the substation powerline, and 3) the mine <br />dewatering system. Figure No. 2, Dorchester Drainage and Sediment Control <br />Plan, shows the location of these sites. <br />The roadside topsoil stockpile is within a 1.22-acre disturbance. The topsoil <br />pile is revegetated to reduce sediment yields; the adjacent area and road <br />flows into a small stilling basin to remove sediment prior to discharge. The <br />substation and powerline areas disturb only a few thousand square feet (0.07 <br />acre) and do not contribute significant sediment. The area around the mine <br />dewatering system is also very small and is being stabilized with a vegetative <br />cover. <br />These areas, because of their location, small size, and insignificant sediment <br />contribution, have been granted small area exemptions by the Division. <br />The Division's review of the drainage and sediment control system, mine water <br />treatment system, temporary water impoundment structures, and alternative <br />sediment control system shows the operation to be in compliance with the <br />design and performance standards of the Regulations. <br />Magpie Creek is a large ephemeral drainage that crosses both the Dorchester <br />and the GEC Mine permit areas. The Magpie Creek stream diversion was approved <br />as a temporary stream diversion during the interim program. It was <br />constructed to divert flow around the surface facilities for the Dorchester <br />No. 1 mine into an unnamed tributary to Magpie Creek to the east of the main <br />drainage. Following the cessation of mining, Magpie Creek would be <br />reconstructed approximately along its original course. <br />