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Mathews <br />Page 4 <br />November 13, 2000 <br />8. Response accepted. <br />9. Response accepted. See Comment lj above regarding the adequacy of the revised SEDCAD <br />demonstrations for the Railroad Loop Area. <br />10. Response accepted. <br />11. Response accepted. <br />12. Response accepted. <br />TR-51 Amendment Adequacy Review Comments <br />1. Response accepted. Please remove the statement from revised page IV-39 indicating that <br />Refuse Area ponds are to be treated as sedimentation treatment facilities. <br />2. Response accepted. <br />3. Response accepted. <br />4. The existing maps in Illustration 44 for Ponds 2-3, and 4, and in Illustration 6A for Pond <br />SA do not provide sufficient detail. There is no scale provided on the maps, watershed areas are <br />not clearly delineated, and some of the ditch segments are difficult to read and not clearly <br />identified. Please revise these maps to show a scale and clear delineation of the watershed and <br />contributing areas for each pond. <br />5. BME has proposed raising the sediment level to within .49 feet, . l l feet, and .13 feet of <br />the primary spillway for Ponds 2-3, 4, and SA, respectively. The SEDCAD 4 Design Manual and <br />User's Guide suggests that a minimum two foot elevation difference exits between the invert of <br />the principal spillway and the top of the sediment storage area. If a slow passive dewatering <br />system is employed, the elevation difference can be reduced to 0.5 to 1.0 ft, depending on the size <br />and flow rate of the dewatering inlet. <br />The Division does not concur with raising the sediment level to within 0.5 feet of the primary <br />spillway. The Division is concerned that sediment laden water out of compliance with the 0.5 ml/I <br />settleable solid limitation may be discharged during a significant storm event as a result of <br />resuspension of previously deposited sediment. To prevent scour of previously deposited <br />sediment from occumng, the ponds should be maintained and cleaned out on a regular basis. The <br />current models estimate that the ponds will need to be cleaned out every three years. <br />