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I I , ., I I I I I I I I I I I I I I I I I ____ ___n_ KISSOURI RIVER KITIGATIOR CALIFORIUA BElID PROJECT RESPONSE TO DRAFT DPR COKKENTS Response to numbered comments 32 through 43 32. The HEC-2 models will be extended downstream by approximately 1 mile using government provided cross-section information as requested. 33. HEC-2 models for the floodplain analyses were calibrated to 100-year water surface elevations shown on the government provided floodplain maps. The CRP could not be reproduced using the existing conditions model calibrated to lOO-year water surface profiles. However, the CRP was closely reproduced throughout the reach by adjusting the starting energy slope. Original calibration of the models was based on information and direction provided to us by the Corps. Some high water mark information was later transmitted to our office just prior to completion of the draft DPR. The HEC-2 model calibrations, split-flow analyses, and floodplain analyses were already completed based upon the information originally provided. Recalibrating the models based on new information would constitute a change in scope. 34. The chute outlet elevation was set slightly more than 5 feet below the CRP so that the chute channel slope would be similar to the average river slope. The chute channel has a slightly longer flow path due to the fact that it is on the outside of the bend. During lower flows, the chute channel flow is hydraulically disconnected from the main channel. The intent of the chute channel slope was to help prevent excessive sediment deposition. 35. See previous comments for Number 32. 36. The conveyance change may cause some problems in the model. however the means for modeling the chute channel should produce reasonable results. 37. The energy grade in the Missouri River decreases very slightly for flows taken out for the chute. The HEC-2 split flow models did account for discharge lost to the chute channel, and flow was reduced in the main channel between the chute inlet and outlet. This is hard to distinguish on the graph since the energy grade is so flat. 38. The EM-1110-2-1601 manual was provided to our office for use on this contract. We were unaware of any updated version. 39. The riprap size will be checked and documented based upon your recommendation. 40. The rip rap size was based on the manual provided to us for use on this contract. 41. The frequency ml.Xl.ng information was originally developed by the Corps of Engineers as a general guideline. The Texas Department of Highways reprinted the information developed by the Corps. In essence. this is the Corps procedure.