2012-07-30_REVISION - C1981012 (2)

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Zach Truiillo - 2 - July 25, 2012 DRMS: Per Table 20, the peak discharge in Ditch 49 (12 %) is 72.33 cfs. If this flows into culvert C85, why is the flow for C85 in Table 21 only 33.51 cfs? NECC needs to submit a copy of the signed (not the draft) temporary use agreement, for insertion into the Right of Entry (Rule 2.03.6) section of the New Elk PAP. Preferably, this will be done before the Division decision on this technical revision. NECC: The design for C85 is based on the 10 -year event because the culvert is off the fill, and therefore not required to be designed for the 100 year event. In addition, please see attached Temporary Use agreement between NECC and CPW, Exhibit 34- (1). The Temporary Use Agreement is also discussed on revised page 2.0.3 -6d. 6. DRMS: The ditch D49 SEDCAD printout is unclear. In the time of concentration details (page EXH19(22) -49), there are two times listed for SWS #2 for Structure #2: 0.055 hour and 0.377 hour. Please explain. It would be very useful (but not necessary) to provide a schematic and /or map showing structures, sub - watersheds, and flow paths for D49 and other ditches. NECC: There are two subwatersheds for Structure #2. One subwatershed is associated with the upland area, the other is associated with the disturbed area that is contributing flow to the channel. The large majority of the runoff in ditch D49 is from the upland area, however, there is a small portion of runoff that will be generated from the berm that will be constructed between D49 and the various portions of the collection ditch on the outslope of the waste pile. DRMS: This portion of the model is still unclear. The NECC explanation does not address why there are two times listed for SWS #2. Furthermore, the Subwatershed Hydrology Detail table lists three SWS's, not two. NECC: Two values were listed for Structure #2. The problem has been corrected, and now only one time of concentration is shown for Structure #2 (Ditch 49- (2 %)). As a result of the change in time of concentration for Structure #2, the peak flow for D 49 -2% has changed as well as all downstream ditch segments. Therefore, please see revised pages EXH. 19(22) -50, 52 to 58, and Table 20 and Table 21. 7. DRMS: The location where ditch D49 would originate was inspected. Please provide more details on the design of the upper end of this ditch to determine if it is sufficient to prevent flow down the drainage from impacting the proposed DWDA. Additionally, it appears that the proposed location of ditch D49 pre - disturbance goes up- gradient at the upper section. Does NECC plan on cutting the slope back or cutting the ditch deep enough to allow flow down the drainage and into ditch D49? NECC: Please see new D49 Typical section on Map 14. A 10' wide by 4' high berm (minimum) will be constructed between D49 and the DWDA diversion ditch. At the