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Sediment storage = 0.1 ac ft/ac (11.35 ac) = 1.135 ac-ft. Total pond volume = 1.55 ac-ft plus 1.135 ac-ft = 2.685 ac-ft. The Division will approve a sediment storage volume less than 0.1 ac-ft/ac only if soil erosion calculations are submitted to verify value used (for example, use U.S.L.E. or M.U.S.C.L.E.). Peak flow calculations do not include a slope adjustment or basin shape adjustment factor as outlined in Appendix E of "Peak flows in Colorado." However, since the spillway was designed far the 100 yr event, there is more than enough conservatism in the design. The Division will therefore not require any adjustment. Spillway sizing: To verify that the spillway has adequate capacity, the Division requires the calculation of head Zoss through the spillway. the headloss should include entrance Loss, bend Loss, friction Loss, and tailwater, if applicable. The alternative to this procedure is to size the spillway using "Federal Highway Administration Homographs" or nomograph pro- cedures from other references such as the Armco pipe design handbook. Information on dewatering method and detention times must also be sumbitted for this pond. B. Pond 9 Calculations: Pond volume calculations must be revised. T/~e sediment storage capacity must be 0.1 ac-ft (44.77 ac-f t) = 4,97 ac-ft unless a lower value is justified using soil loss calculations. Information on detention time and method of dewatering must be included. Spillway designs: Because the spillway was designed for a 100 yr. •svent the sltlpe adjustment and basin shape correction factor will not be required. However, the culvert spillway design must include information on head loss as previously mentioned in Pon 1 comments. C. Diversion Ditch Calculations: We were unable to determine whether the diversion ditch on Figure 8 is a permanent or temporary diversion. If the ditch is permanent, the peak discharge calculations must include a basin shape and slope adjustment correction factor. The ditch must also incorporate 0.3 ft of design freeboard. And additional capacity for vegetated conditions must be included in the ditch design. Diversion ditch culvert design must include information on head loss due to entrance loss, friction loss, and tail water. Maximum allowable head is a main consideration. The ditch is only 1.0 feet deep yet a 2.5 foot culvert is used. It is obvious that the ditch will overflow before the culvert flows full. This situation must be remedied. (Several small culverts might be appropriate.) (6)