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<br /> <br /> <br />Ponds F and G do not need baffles, according to <br />calculations based on the method suggested in the <br />EPA publication Erosion and Sediment Control, <br />Surface Mining <br />sign, pp. 65 to <br />the Eastern U.S., Vol. <br />In this method, the ratio of length to equivalent <br />width (L/We) is kept above 2.0 by proper design of <br />the pond, or by installation of a baffle between <br />the inlet and outlet. Equivalent width, We, is <br />defined as the surface area of the pond at normal <br />pool elevation (elevation of lowest set of holes <br />in the outlet) divided by flow length, L, or We = <br />A/L. (Calculations and Figure 1 in Appendix C, <br />Exhibit 13) show that these ponds have kept L/We <br />above 2.0, and should not need baffles. Perhaps <br />these ponds appear inefficient due to the way they <br />were drawn on EFC Map 13, where the ditches and <br />embankments were shown schematically and not <br />exactly as designed. LRCWE Map 1, which shows the <br />pond configurations as designed by LRCWE has been <br />added to the backup calculations in Appendix B of <br />Exhibit 13. <br />Baffles will be required for ponds D, N, P, Q and <br />R according to our calculations. The proposed <br />baffle design is shown on LRCWE Figure 1, along <br />with a schedule listing appropriate dimensions. <br />LRCWE Figure 1 and the calculations have been <br />added to Appendix C of Exhibit 13. <br />See, also, p. 816-46(a) <br />12/20/79 Memo, p. 1, 1k4 <br />"4. Sediment calculations for Pond A were based upon <br />the year 1980. Why was this year selected? Pond <br />sizing should be based on the worst case during the <br />life of the pond. Do the calculations for the year <br />1980 meet worst case conditions?" <br />