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<br />7 <br />38. Appendix 5 Table 6-2. Only four of the 10 cross sections analyzed have an acceptable <br />FOS for global stability. The response is not adequate. CC&V must commit in <br />writing to modify and implement the angles and bench configurations listed in Table <br />1-1 of the CNI report. <br /> <br />RESPONSE: Using updated drilling information, CC&V will modify and implement <br />recommended slope angles based on updated slope stability analyses as seen in Table 1- <br />1 of the Appendix 5. <br /> <br />Volume IV – Appendices 9 through 14 <br />53. Appendix 10, Chicago Tunnel Site Detention Pond (p. 6). Please re-evaluate and re- <br />design as appropriate all AM-11 ponds and their spillways. The response is not <br />adequate. The SEDCAD model input (p. 7) in Attachment 13 indicates the sediment <br />pond is empty at the onset of the design storm. The Division’s engineer is all too familiar <br />with the CC&V pond design criteria as he designed several of them in the 1990’s. <br />Regardless of the design volume of the pond, the pond must be designed to pass the <br />100-year design flow assuming the pond is full to the lowest, non-gated, gravity flow <br />outlet structure, unless it can be demonstrated the pond will be empty at the onset of <br />the 100-year, 24-hour design storm. Pursuant to Rule 7.3.1(3), please confirm the <br />proposed 8-foot wide armored spillway at the one-foot freeboard depth cut is designed <br />to safely convey the full design peak flow to a point past the toe of the embankment. <br /> <br />RESPONSE: CC&V is in the process of running calculations to address the Division’s <br />comment and plans to provide a more detailed response to the Division by December 27, <br />2016. CC&V will submit a TR to re-evaluate AM-11 ponds and spillways during 2017. <br /> <br />57. Appendix 10, Drawing CCVSA11-6. There are some discrepancies in the channel <br />details: <br />a. Details 2, 3 and 4 show channel and swale freeboard designs. The response is <br />not adequate. Pursuant to Rule 7.3.1(3), “Design capacities shall be sufficient to <br />handle the design storm event for the area”. A sufficient design includes <br />freeboard to compensate for the many unknown factors that could contribute <br />to errors in the predicted peak flow and/or deficiencies in construction of the <br />conveyance structure. If the stated traffic area is graded to drain to the swale, <br />is wide enough and has sufficient fall to prevent local ponding from pushing <br />flows outside the “ChiTunPond Basin” into the “ChiTunBypass Basin” channel, <br />then that needs to be explained and shown in Details 2, 3 and 4. Otherwise, <br />freeboard must be included in the design. <br /> <br />RESPONSE: CC&V is in the process of running calculations to address the Division’s <br />comment and plans to provide a more detailed response to the Division by December 27, <br />2016.