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n NVIRGNMENY'AL IMPAU'IREYURT' ADDENDUM ARMSTRONG RANUII REVISBD YRGJEU'r <br />'SEPTNM BEN ]1f} SANTA ANA. DALIFDRVIA <br />design geotechnical report and compliance with tecoinniendations'of the final'desiam <br />guotechnical.report: Mitigation MeasureGEO-2 requiiescompliance with the: Californih <br />Building Cade, which stipulates appropriate seismic iesign provisions that. shall be <br />implemented with design and construction of the Revised Project. Mitigation Measure <br />GF,O.4 requires that a registered geologist ensure that that project adheres to the <br />recommendations of die final design guolechniaal report.' Implementation of Mitigation <br />Measures GEO-1, GE6-2, and 6EO.4 would reduce.any, potential impacts related to strong <br />seismic ground shaking to a less"than significant level. The Certified EIR.also,concluded that <br />Mitigation Measures GEO-1, GEO-2, and GEO.4 would reduce impacts related to strong <br />scismic'shaking to a less than significant luvel. Therefore; the Revised Project would not <br />result in new significant impacts beyond those identified in the Certified EIR. No new <br />mitigation measures are'requirm . <br />(iii) According. to the State of California Seismic Hazard Zones map, the Project site is loaded in <br />a liquefacrion zones In addition,_acctirding to the City of Santa" An General Plan, Seismic <br />Safety Element (1982; reformatted 2Q10), the Prgiect site is loctated in a potential liduefction <br />arca'. However, the Geotechnical Investigation Report prepared for the Certified EIR <br />concluded, that the Project siie ha' s a low potential for liquefaction' and that liquefaction is <br />unlikely to occur..Thurcfore; impaets of the Revisud Project related to, liquefaction during a <br />seismic event would.bc less than "signiricant.and no mitigation is required. <br />Strong ground shanking can cause soil settlement by allowing sediment particles to become <br />more tightly,packed, thereby reducing pore space: The Geotechnical Investigation Report <br />prepared for the Certified EIR (concluded that diene is a very low to non-existent potential for <br />ground settlement on the Project site during a scisntic'eventTherefore, impa'ct's of the <br />Revised Project related to seismic -related ground failure, during a seismic event would be less <br />than significant and no mitigation is required. <br />Lateral 'displacetiient of surticial blocks of sediment can occur as a'result of liquifaction in a. <br />-subsurface layer. -The Preliminary Geotechaical Investigation Report prel6ad for the <br />Certified EIR concluded that there is a low probability of` lateral spreading to occur on the <br />Project site during it seismic event. Therefore, impactrelated to lateral spreading during a <br />seismic event would be less than significant and no mitigation is required, <br />If near surface soils Vary in composition, strong earthquake shaking carr cause non-uniform <br />compaction of the soil, resulting in movement of the near -surface soils which can result in <br />differential compaction. The Preliminary Geotechnical Investigation Report prepared for the <br />Certified EIR concluded that there is a ld%v probability of differential compaction to occur on <br />the Project site. However, the Certified EIR also concluded that strong earthquake shaking <br />could cause non-uniforn compaction of the soil which could result in damage to on-site <br />structures. Therefore, there is a potential for the Revised Project to be impacted by <br />differential compaction -during a seismic event. <br />The Revised Project would be"required to comply with Mitigation Measures GEO=1, GE -O-2, <br />and GEO-4 trout the Certified EIR. Mitigation Measure GEO-1 requires preparation of a final <br />State of California, lltvision or Mines and Geology. 1998, Seismic Hazard Zones. <br />I'^.$n0160441Jdmdmn',.gddeNJum.Jm:x caY1ar l7u <br />75B-79 <br />2-30 <br />