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The following is an additional response under Section 2.05.3(2) as found in <br />Appendix E dated October, 1981. <br />The calculation for peak flow at culvert No. 8, as shown, is very conserva- <br />tive. For the calculation, a CN of 90 was used. In fact, from Table 5,2 <br />in Reference No. 2 and assuming 5% cover and a B soil type, a CN of 82 can <br />be used. The calculation then will become as shown below: <br />T = 0.34 hours <br />c <br />Drainage = 93.4 acres = 0.15 square mile <br />Runoff = 0.52 inches (1.8 inches rainfall CN82) <br />Peak Flow (from Figure 5,2, Reference No. 2) = 650 csm/in <br />650 cfs/sq.mi. x 0.15 sq. mi. x 0.52 = 50.7 cfs <br />inches <br />= 22.700 gpm <br />• From the upstream invert elevation to the edge of the road 5.2 feet of head <br />is available. Therefore, 4.2 feet head is available for the culvert <br />assuming a minimum of one foot freeboard. The capacity calculation is <br />shown below: <br />Assume C = 60 <br />Head = 160 x 4.2 = 7 ft/100' pipe <br />Capacity of 30" pipe = 31,000 gpm <br />31,000 gpm > 22,700 gpm <br />.: existing pipe is sufficient <br /> <br />M133 <br /> <br />