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ENVIRON MEATAL IXPACT REP O nT AHQP.NII QX AQXSTµ ONO-µAF011 AGYf JE➢ PROJECT <br />SHPTPMIlCA 9419 SANTA -ANA, CALIPOQKIA <br />c) During construction activities„soil would be compacted -and drainage patterns would he <br />temporarily altereH during grading and other construction'acngitics, and therewduJd bean <br />increased potential for flooding compared to existing conditions. As discussed in Response 2.8.a <br />and specified in Mitigation Measures GE0-5 and GP.6-6 from the Ccriificd EIR,,the Revised <br />Project would comply with the requirements of the Construction General Permit,' Vhich includes <br />preparation of a SWPPP to implementation of Constructioth BNIPs to reduce impacts to water <br />quality during construction, including those impacts associated with flooding. lmplementation of <br />the Mitigation Measures GEC -S and GEC -6 would reduce construction impacts related to on- or <br />off-site flooding to less than significant. <br />The Revised Project would increase impervious surface on the Project site which would increase <br />the volume of runoff train the Projectsite compared to existing conditions. The Revised Project <br />would be required to comply with t1ie County MS4 Pennit and hydromodification requirements, <br />which require jhat post-constnietion runoff be reduced to less than or equal to existing conditions. <br />in addition; the Revised Project would comply with Mitigation Measures HYD -I through HYD -3' <br />of the Certified EIR, which require drainage improvutnents to address' increases imstormwater <br />runoff, Compliance with the County MS4 Pennit and hydromodification requirements and <br />implementation of Mitigation Measures HYD =I through HYD -3 would reduce impacts related to <br />stortndrain capacity and downstrearn flood nto a less than,significa' level. In'addition, any <br />proposed RMPs and on-site storm drain. facilities include in the design of the Revised Proj= <br />would be sized to accommodat stonn water runoff from the Project site so that on-site flooding <br />would not occur. Finally, the Rev'ised'Pmject would not alter the course of a stream or river- in <br />summary, inhpleinentalion of Miligaiion Measures GE0-5, GE6-6 and HYD113hroughliYD-3 <br />would reduce construction operational impacts related to on-site or off-site flooding to a less than <br />significant level. The Certified EiR also concluded that with implementation of mitigation, <br />impacts related to alternation of drainagcpatters and flooding would be reduced to a less than <br />signifcantlevel. Therefore, the Revised Project would not result in new signi.ftcant impacts <br />beyond those identified in the Certified EiR. No hew thtitigation measures are required. <br />(1) Thu Revised Project would increase impervious surface areas on the Project Si(a, which would <br />ifurcaw the volume of stoim water runoff generated from the. Project site. Increased volume and <br />peak flow of runoff fromthe Projectsiie has the potential to exceed the capacity ofdow'nsfream <br />slotmdrain systems. lleRevised Project would be required to comply with the County, MS4 <br />Permit and hydromodification requirements, which require that post-conslruccioa.runoff be <br />reduced Lo fess than or equal to existing conditions. In addition, the Revised Project would <br />comply with 41htigntion Measures HYD -I through IIYD-3 of the Certified EIR, which require <br />drainage improvements to address increases in stonnwater runoff. Compliance with the County <br />1094 Permit and hydromodification requirements and implementation of Mitigation Measures <br />HYD -I lhniugh HYD -3 would reduce impacts related to stormdrain capacity to a less than <br />significant level. The Certified EIR also concluded that the Approved Project wouldhave a less <br />than significant impact related to the capacity of downstream stormdrains with implanentation of <br />Mitigation HYD -1 through HYD-3.1lterefore, the Revised Project would not result in new <br />significant impacts beyond these identified in the Certified EIR. No new mitigation measures are <br />required. <br />e) The Project site is not located in a 100 -year special flood hazard area. According to the City of <br />Santa Ana General Plan, Public.Satety Element (1982, reformatted 2010), the Prgiccl site is. <br />P.%SI IU 16414-Addendum'.Addendum.doex 0,7. l7„ <br />75B-94 <br />2-45 <br />