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6. The following comments relate to the sediment pond design: <br />a. How were curve numbers derived? <br />Response: Curve numbers of 90 for disturbed areas and 72 for <br />undisturbed areas have been determined based on the soil type and <br />vegetation type and cover of the undisturbed area and the <br />configuration of the disturbed area. <br />b. The accepted standard for sediment volume is 0.1 acres of <br />disturbed area. Unless Peerless can justify the use of 0.05 <br />acre-ft/acres, the pond design must be revised. <br />Response: Given the configuration of the disturbed area, the <br />design criteria of 0.05 Ac-Ft per acre for determining sediment <br />volume is adequate. No continuous surface mining or surface <br />disturbance is planned or necessary at the Coal Gulch Mine. <br />Surfaces shown as disturbed are primarily covered with gravel or <br />other material with contributing little or no sediment during <br />runoff. Only the coal stockpiles will contribute sediment to the <br />sediment pond. Management of the sediment pond will occur in such <br />a manner as to remove accumulations of sediment on a regular basis. <br />Annual or semi-annual cleaning may be required to maintain adequate <br />sediment storage volume in the system. <br />c. The pond needs a dewaterina device. <br />Response: The sediment pond has a dewatering device in that the <br />principal spillway is located at the design sediment level. <br />d. Based upon site inspections, the Division feels that the pond <br />is losing water faster than water is entering the pond. <br />Peerless should investigate this to determine where this water <br />is going. Remedial measures may be necessary to prevent pond <br />. leaks e. <br />-10- <br />