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3. Temporary culverts, ditches, catch basins, dams and settling ponds will <br />be installed in the street construction areas to maintain existing <br />lir- ainaRP flnlm. nnd to collect excess water and sediments flowing out of <br />the construction sites. Sediments collected will be disposed of at a <br />Class II or Class III disposal site. <br />D. FLOODPLAIN,IFLOODWAY ENCROACH <br />As identified in Section III.A.4 and Figure 12, two portions of the project area <br />are subject to flooding from a 100 -year episode storm (designated as Zone "A" <br />by the Federal Emergency Management Agency's (FEMA) Flood Insurance <br />Rate Maps (FIRM). <br />The risks associated with the Santa Ana River floodplain at the southerly <br />periphery of the project area and the Santiago Creek' are minimal. Please <br />refer to Sections III.A.5 and IV.G for further information on biological „ <br />resources. The widening of the Santiago Creek Bridge would entail very <br />minor encroachments into the creek, which will not affect the floodway as long <br />as the existing bridge elevation is maintained. Please refer to the discussion of <br />the bridge improvements in the following section concerning streambed <br />modification. The proposed Santiago Creek Bridge improvements will be <br />designed so that those portions encroaching into the regulatory floodway will <br />be consistent with the standards established in FEMA's Flood Insurance Study <br />(September 15, 1989) and administered by the City of Santa Ana. <br />MP <br />The project is not a longitudinal encroachment into either of the two flood <br />plains and the project will not affect probable incompatible floodplain <br />development. There are no significant impacts on natural and beneficial ., <br />floodplain values, including biological resources. The proposed action does <br />not constitute a significant floodplain encroachment, nor a significant effect on <br />a regulatory floodway. .., <br />Mitigation Measures <br />Routine construction procedures will be implemented to minimize impacts to <br />the floodplains. With regard to the bridge over Santiago Creek, the design <br />will consider the possibility of the Creek overtopping its banks and will be ... <br />designed to withstand such an episode. <br />There are no special mitigation measures necessary to minimize impacts or �- <br />restore and preserve natural beneficial floodplain values. <br />IV -4 <br />w <br />