914-918 N Bewley St - REV 1 - Plan

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Illumination Foundation Santa Ana, California Hydrology Report by TAIT & Associates TAIT JOB # SP9104 Page 6 Orange County Local Drainage Manual as discussed in Section 2.1.2 in this report. The finished floors are at 82.62’ in the 3 westerly structures and 81.60’ for the existing building to remain towards the frontage of the property. To address ponding related concerns a hydrograph was developed for the 100-yr storm event in the proposed condition to evaluate runoff volumes. The AES Hydrograph output can be found in Appendix E. The total volume of the 100-yr storm in the proposed condition resulted in 0.34 AC-FT or 14,810 CF of stormwater runoff. The average flowrate for the 100-yr event prior to peak is roughly at 0.5 CFS and thus the 0.5 CFS pump was specified on the storm drainage plan. With a storm drainage pump operating at 0.5 CFS or 1800 CF-HR the pump would drawdown the entire 100-yr volume in roughly 8.23 HRs well below the required 48-hr drawdown due to vector concerns. During the storm peak there is expected to be some pondi ng during short periods but will not inundate any surrounding structures before existing the site at the south easterly corner. Outfall 2 sees a reduction in peak flows of 30% and 32% in the 25 -year and 100-year storm events. Based on the results of this study, the project development will not create an increase in runoff. Therefore, the proposed project improvements will not have an adverse effect on the downstream storm drain system. 914-918 N Bewley St5/8/2025