EX Flow 2240719_JC_JF_Memo

Project No. 24006174A July 19, 2024 Page 6 | 9 Pre-Existing 12” Pipes Existing 36” Elliptical Pipe Proposed OCS 2 Year 11.20 cfs / 14.15 fps 11.20 cfs / 16.06 fps 11.20 cfs / 13.94 fps 10 Year 22.77 cfs / 16.07 fps 22.79 cfs / 20.10 fps 13.62 cfs / 14.23 fps 25 Year 24.13 cfs / 16.07 fps 31.05 cfs / 22.13 fps 13.62 cfs / 14.23 fps 100 Year 22.14 cfs / 16.07 fps 43.54 cfs / 25.01 fps 15.30 cfs / 14.23 fps Figure 6: Outfall Flow Chart Another item of concern that we feel requires immediate attention is the completion of the stone retaining wall. Based on correspondence and conversations with the owner it is our understanding that the top layers of stone are temporary and intended to be removed with the restoration of the adjacent grades. We learned that the site contractor overcompensated to contain the site drainage to assure that there was no stormwater runoff from the area under construction. Once the construction was completed, the temporary part of the wall was to be removed and the grades restored. The below site photo shows that the top 4-6 feet of the wall is not mortared. When the temporary top courses are removed the grading on both sides will be restored and compacted in accordance with industry standards. The foundation of the wall will be buried, and the final wall from foundation to top will have a maximum height of 6’ in limited areas and the height sloped off as intended. Figure 7: Current Wall Conditions per Omland and Osterkorn Interim As-Built