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Adequacy Letter - TR 65 <br />September 17, 1993 <br />Page 2 <br />5. Why was D2R-3 at slopes less than 3.5 percent modeled using <br />clear water when this ditch is a sediment ditch? When it is <br />modeled with sediment laden water, the channel is incapable of <br />passing the flow. The design for this ditch should be <br />reviewed again. <br />6. D2R-2 was previously sized according to an upper reach with a <br />steep slope and lower reach with a flat slope. This sizing is <br />noted in revised Table 44 but included with the SEDCAD runs as <br />only a flat slope. Should the Exhibit include both sizings? <br />7. D2R-lA should be sized for 3.45 cfs as it collects flow from <br />watershed 18D. The size of the ditch does not change <br />drastically with the increased flow. This flow was obtained <br />from the model currently provided in Exhibit 66 for watershed <br />18D. (See also question 1 under ponds.) <br />8. Discharge for D2-1 needs to be increased as the ditch carries <br />water from D2-2, C2-2 and WS14A. <br />Culverts• <br />1. Flow into C2R-2 should be increased as this culvert carries <br />water from D2-1 and D2R-2. It appears that the size of the <br />culvert will not change with the increased flow. <br />Pond: <br />1. With this revision, MCC provided the Division with a model for <br />watershed 18E, but this watershed is not on Map 54. Watershed <br />18E is currently in Exhibit 66 modeled with watershed 18D for <br />a 10-year event. As this area is within the refuse pile <br />drainage area, which is sized for a 100-year event, does this <br />model need to remain? In addition, watershed 18D was modeled <br />for the 100-year event. Please clarify as to whether i8D or <br />18E should remain in Exhibit 66. <br />2. Why has another watershed 31 has been added in the vicinity of <br />watershed 21? What area does this watershed include? This <br />new watershed has not been included on Table 42, nor is there <br />an output for this watershed. MCC should provide the Division <br />with information on this watershed. <br />3. The Division does not have watershed runs for watersheds 5C, <br />5D, and 13 F. Please provide to the Division. <br />4. From review of the watershed runs for watershed 13, it appears <br />that the acreage and curve numbers need to be increased in the <br />~- <br />