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9. Anti-Seep Collars. The commitment to provide an an ani:i-seep coTTar on u ver No. HR-3 as noted in the response and as shown in the Appendix satisfies this adequacy concern. 10-11. Culvert HR-6. The operator has proposed to install a 24-inch cu ver al-phis location and allow overflow to pass down the ditch to the 54 inch culvert. This was the original proposal submitted October 6, 1989. The other option presented by the Division to install a 36-inch culvert was rejected unless all parties relieve the operator of liability for damage which may occur to Cedar Heights Drive. The Division requested that a demonstration be provided that the ditch segment between HR-6 and the 54-inch culvert is non-erodible at the design conditions specified. The Appendix identifies that 39 cfs will be bypassed and flow down the ditch during the 25-year storm. This is a considerable amount of runoff to be carried by a roadside ditch. The information to demonstrate the ditch is to be constructed with sufficient size and that it is non-erodible has not been provided. Ditch dimensions and size of riprap should be specified. This adequacy concern remains unresolved. The Division also requested a demonstration that the 54-inch culvert could handle this additional flow. The operator has stated this is the responsibility of others. This statement appears to be consistent with our previous interpretation of local drainage law. Although some uncertainty remains ~xhether the 54-inch culvert can handle the flow under the proposed drainage and culvert system, the response as far as the Division is concerned has been addressed. 12. Inundation Area. The operator has proposed two (2) alternatives ot• `r`~"li Ting tie inundation area without discharging sediment-laden water downstream: (1) backfilling the pond during ice cover followed by finish grading during the spring; and, (2) building a temporary silt fence. Both of these were offered as ,~n alternative to pumping water from the inundation area t~~ the proposed silt pond. Both offer the advantage that they can occur prior to construction of the silt pond which is n~~t likely to occur till next spring if approved. The operator has apparently misunderstood my recommendation to install a 6 to 9 inch granular filter layer on the sediment in the pond prior to placement of channel riprap. The reference to "filter layer" was as a bedding for riprap--not as a sand filter for trapping sediment. The silt fence would not trap very fine particles, only coarser sediment, and may not serve the intended function. The proposal to work during frozen conditions has merit as was explained and would be acceptable.