Item 18 - Appeal Application Nos. 2023-02 and 2023-03 for Cabrillo Town Center project

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development that would substantially alter drainage patterns because these areas are already developed with existing uses and impervious surfaces. However, limited development of land that is currently vacant (i.e., agricultural parcels) and covered with permeable surfaces may occur. Although minimal, increased impervious surfaces would increase stormwater runoff in the Overlay Zone. In addition, it is unknown whether the existing drainage system throughout the Overlay Zone is adequate. Therefore, in order to provide a conservative assessment, it is possible that this increased runoff could exceed the capacity of existing and planned infrastructure and cause downstream flooding impacts. The Certified EIR stated that adherence to Mitigation Measure MM-OZ 4.7-1 would require the preparation of a WQMP and implementation of appropriate BMPs, which could incorporate stormwater detention facilities, and would reduce the volume of runoff generated (and potential for flooding) in the Overlay Zone. However, because the existing capacity of the existing storm drain system in the Overlay Zone is unknown, it was determined that this impact could be potentially significant. Implementation of Mitigation Measure MM-OZ 4.7-2 is required to address these issues. Impede/Redirect Flood Flows The Certified EIR stated the Overlay Zone is not within the 100-year flood hazard area and is outside the 0.2 percent annual chance floodplain. As there would be no risk of flooding in the Overlay Zone, there would be no impact to the placement of structures which would impede or redirect flood flows, and no impacts will occur. Tsunami/Seiche Water Quality Hazards The Certified EIR stated Overlay Zone is located approximately 9 miles from the Pacific Ocean and 130 feet above sea level, which is a sufficient distance so as not to be subject to tsunami impacts. No impact associated with tsunamis is anticipated to occur. The closest enclosed bodies of water that could result in earthquake -induced seiches are the Prado Dam, which is located near the City of Corona to the northwest of the Cleveland National Forest, or the Santiago Dam, which is located approximately 12 miles east of the area in Silverado. The project site is not located within a flood hazard (inundation) area associated with either dam. Therefore, overflow as the result of a seiche would not expose people or structures to a significant risk of loss, injury, or death involving inundation by seiche within the Overlay Zone. The City is located on nearly flat surfaces and there are no areas with slopes significant enough to cause mudflows near the Overlay Zone which would expose people or structures to a significant risk of loss, injury, or death. Therefore, no impact associated with mudflows is anticipated to occur. In summary, it was determined that there will be no impact to the exposure of people or structures at the Overlay Zone to a significant risk of loss, injury, or death involving inundation by a seiche, tsunami, or mudflow. Mitigation Measures MM-OZ 4.7-1 In order to comply with the 2003 DAMP, future development projects in the Cabrillo Town Center City of Santa Ana Technical Memorandum August 2023 City Council 18 — 585 10/3/2023