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D. T. Mathews - 2 - November 2, 2000 b. The contributing areas for the SEDCAD demonstrations for the east and ~,,,tl~~r west sections of the permanent diversion ditch are presented on page CRDA2-12b. ~c. The riprap size for the east and west sections of the upper diversion ditches was reevaluated utilizing the Simons/OSM method. Revised pages CRDA2- 13d & 13j are enclosed. This also changed the design flow depth. Energy dissipaters have been designed for the transition of flows from the permanent diversion ditch to the natural drainages. The dissipaters will be 10-feet wide by 30-feet long and will be constructed utilizing the riprap size presented on pages CRDA2-131 & 13m. e. Page 14-11 was revised to explain how the cover material obtained from the ~~ -~ ditch excavation will be tested for pH, EC and SAR. Unsuitable material will be covered with additional material obtained from CBA-2. 7. No response required. 8. No response required. 9. Exhibit 60 presents the plan to remove the Coal Creek diversion rock check dams. The rock and sediment will be utilized for reclamation. Exhibits 53 and 60 present the alignment of Coal Creek and the section of its embankment that will be fortified na`'~ with riprap. Based on meetings with the DMG and BLM, the upper dip section will remain with the installation of cut-off walls (requested by the BLM) as shown on Exhibit 19 & 60. The cut-off walls are 10-feet long and as tall as the concrete which encases the culverts. The walls will be constructed on the downstream end of the dip section so they will retain material. They are designed structurally as retaining walls. 10. Item 9 above references the installation ofcut-off walls at the upper dip section. No ~~ other modifications should be necessary for the BLM to accept responsibility for 1) the two 81 " X 59" culverts; 2) the dip section comprised of six 36" culverts encased in concrete with cut-off walls added and; 3) the 72" culvert, all located along/under haul road number 4. 11. No response required. 12. The SEDCAD demonstration submitted for the UTL Silt Fence #2 was opened and I also obtained the result of 0.58 ml/I of settleable solids. Enclosed is a revised ~ SEDCAD demonstration which results in 0.05 ml/I of settleable solids. The length of the silt fence must be increased to 130-feet to meet this settleable solids limitation. Exhibit 11 C was revised accordingly. I have no idea why the program gave me incorrect information.