Draft Environmental Impact Report - East Bay Municipal Utility District

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Estates Reservoir Replacement Draft Environmental Impact ReportGeology, Soils and Seismicitysteep slopes that are susceptible to strong ground motion during an earthquake. The1989 Loma Prieta earthquake triggered thousands of landslides over an epicentral areaof 770 square miles. The Oakland-Berkeley Hills could experience some earthquakeinducedrockfalls, slumps, and debris flows during an event on the Hayward Fault orother active Bay Area fault capable of generating strong ground motion. There is nomapped or known active landslide in the Project area; therefore the likelihood ofexperiencing a secondary earthquake hazard at the Estates site is very low.3.3.3 Impacts and Mitigation MeasuresSignificance CriteriaIn accordance with Appendix G of the CEQA Guidelines, a geologic or seismic impact isconsidered significant if it would:Expose people or structures to potential substantial adverse effects, including therisk of loss, injury, or death involving:- Rupture of a known earthquake fault, as delineated on the most recent Alquist-Priolo Earthquake Fault Zoning Map issued by the State Geologist for the areaor based on other substantial evidence of a known fault- Strong seismic ground shaking- Seismic-related ground failure, including liquefaction- LandslidesResult in substantial soil erosion or the loss of topsoil;Be located on a geologic unit or soil that is unstable or that would become unstableas a result of the Project, and potentially result in on-site or off-site landslide, lateralspreading, subsidence (i.e., settlement), liquefaction, or collapse;Be located on expansive soil, as defined in Table 18-1 -B of the Uniform BuildingCode (1994), creating substantial risks to life or property;Have soils incapable of adequately supporting the use of septic tanks or alternativewastewater disposal systems where sewers are not available for the disposal ofwastewater;Result in the loss of availability of a known mineral resource that would be of valueto the region and the residents of the state; orResult in the loss of availability of a locally important mineral resource recoverysite delineated on a local General Plan, Specific Plan, or other land use plan.Based on the geologic environment in the Project area, the proposed Project would not beimpacted by fault rupture, ground shaking, liquefaction, expansive soil, wastewaterdisposal, or mineral resources. No impact discussion is provided for these topics for thefollowing reasons:Fault Rupture - The faults most susceptible to earthquake rupture are active faults,which are faults that have experienced surface displacement within the last 11,000years. There is no known active fault crossing the Project site. The nearest activesb09_001.doc 3-3.12 7/22/2009
Estates Reservoir Replacement Draft Environmental Impact ReportGeology, Soils and Seismicityfault (Hayward-Rodgers Creek) is approximately 900 feet to the east of the site,based on maps produced (Figure 3.3-1). Therefore, the potential for fault ruptureto affect the proposed Project is very low.Ground Shaking - One purpose of the Project is to eliminate any seismic instability ofthe existing dam. Therefore, the Project itself would significantly reduce the potentialfor injury and damage from ground shaking and is considered a beneficial impact.Liquefaction - Existing materials beneath the dam and the reservoir basin are notsusceptible to liquefaction (URS, 2006).Expansive Soil - The new concrete tanks will either be supported by pier foundationsor engineering fill embedded in bedrock. Any expansive soil at the site would notaffect the structural performance or cause potential risk to life or property.Wastewater Disposal - None of the Project elements require the use of septic orother alternative disposal wastewater systems; therefore, no impact associated withthis hazard would result.Mineral Resources - None of the Project elements would alter, destroy, or limitaccess to any existing mineral resources.Impacts and Mitigation MeasuresImpact 3.3-1: New slopes associated with reservoir construction may be potentiallyunstable.The proposed Project will entail excavation of the existing ground and dam embankmentand will create temporary cut slopes and new fill slopes around the tanks. Withoutadequate design, the new slopes may be unstable, a significant impact.Measure 3.3-1: During the design phase, EBMUD will perform a geotechnicalevaluation and, if required, conduct site-specific geotechnical investigations to reduce oreliminate potential slope hazards. Design and construction specifications will incorporatethe recommendations from the geotechnical evaluation for any slope stabilization, whichmay include some of the following measures, although this list is not exclusive:Appropriate slope inclinationSlope terracingFill compactionSoil reinforcementSurface and subsurface drainage facilitiesRetaining wallsButtressesErosion control measures- Soil nails or anchors- Sub drain systemSignificance after Mitigation: Less than Significant.sb09_001.doc 3-3.13 7/22/2009
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Estates Reservoir ReplacementDraft
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TABLE OF CONTENTSEstates Reservoir
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Estates Reservoir Replacement Draft
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ACRONYMS AND ABBREVIATIONSABABAGAPC
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SUMMARYS.1 IntroductionThis Draft E
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Estates Reservoir Improvements Draf
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CHAPTER 5Cumulative Impacts, Growth
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CHAPTER 6Report Preparers6.1 Lead A
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APPENDIX APublic InvolvementPublic
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APPENDIX BNotice of PreparationAUGU
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Dingee Pressure Zone Improvement Pr
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FIGURESDingee Pressure Zone Improve
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Draft Environmental Impact Report - East Bay Municipal Utility District

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