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Ms. Sandy Emrich • -2- ~ November 26, 1982 6. Problems were identified with Table B, Exhibit 6 with regards to culvert sizing. The manning open channel equation is only applicable to a depth of flow of 94Y of capacity, after which closed conduit hydraulics apply. Culvert designs should be rechecked using an appropriate closed conduit design procedure. 7. Page 4.05-19 of Volume 1 and page 3 Exhibit 6 of Volume 2 state that the Division approved a sediment storage criterion of 0.02 ac-ft/ac of disturbance. On January 29, 1982 for the CYCC mines. This statement is incorrect and should be deleted from the applications. When this criteria was proposed in the winter of 1981-1982 the Division responded with a letter of concerns that needed to be addressed prior to our approval of the criteria. That letter was dated December 10, 1981 from Sandy Emrich of MLRD to Kent Watson of CYCC. Instead of taking the time to respond to this letter CYCC instead chose to pursue a quick solution to the issue by developing a sediment yield criteria for a specific sub-watershed. The response was contained in a letter dated December 11, 1982, from Michael McCarthy to Sandy Emrich (hand deliveral) The Division reviewed this criteria and found it to be acceptable for that particular watershed. However, approval was never granted to allow its use over the entire basin. Topographic (LS) factors vary too much to allow such a site specific criteria over a wide region. It should be noted that the Division reviewed the sediment ponds considering the old sediment storage criteria (o.l ac-ft/ac disturbance). The Division found that the structures will still be capable of storing the required sediment, runoff, and mine water. Therefore no actual design modifications will be needed. The Division however, encourages CYCC to pursue a uniform sediment storage criteria either now or in the future.