Draft Environmental Impact Report - East Bay Municipal Utility District

Estates Reservoir Replacement Draft Environmental Impact ReportGeology, Soils and Seismicity3.3 Geology, Soils and Seismicity3.3.1 Approach to AnalysisThis section evaluates whether construction and operation of the proposed EstatesReservoir Replacement Project would result in potential adverse impacts related to localgeology, existing soil conditions, or seismicity. The analysis is based, in part, on reviewof various geologic maps and reports (note references at end of section) and otherliterature.3.3.2 Setting/Regulatory FrameworkRegulatory JurisdictionSince 1929, the State of California has supervised the construction and operation of damsto prevent failure and to safeguard life and property. The California Division of Safety ofDam (DSOD) supervises the construction, enlargement, alteration, repair, maintenance,operation, and removal of dams and reservoirs. DSOD has jurisdiction over all dams inthe state that are not federally owned, that are 25 feet or higher, and that have a storagecapacity of 50 acre-feet of water or greater, with the exclusion of the dams that are 6 feetor less in height (regardless of storage) and the dams with a storage capacity of 15 acrefeetor less (regardless of height). DSOD conducts annual inspections of dams under itsjurisdiction and periodically requires that they are evaluated with respect to safety andseismic stability (Wahler Associates 1980; Fraser and Howard, 2002; URS, 2006).DSOD also mandates corrective measures, if required, to ensure the safe operation of thefacility. Based on the URS 2006 report, the estimated crest vertical settlement for theHayward Fault maximum credible earthquake is between 3-4 feet. This crest settlementis not judged to provide an adequate margin against potential overtopping of theembankment if the reservoir was full during the earthquake.DSOD has regulatory jurisdiction over the existing Estates Dam. As a requirement forthe continued operation of the Estates Dam, EBMUD submits an annual instrumentationperformance report to DSOD for review and approval. In 2006, EBMUD proposed toDSOD that the elevation of the Estates Reservoir would be lowered seven feet below theEstates Dam crest, to increase safety from excessive settlement of the crest. In early2007, DSOD accepted EBMUD’s proposal as an interim measure, with the understandingthat EBMUD would continue to aggressively pursue a schedule for permanentremediation. EBMUD subsequently notified DSOD that the Estates Dam would beremoved from service by 2013, and would continue to operate seven feet below the damcrest in the interim. DSOD accepted this proposal. The Estates Dam will be removedfrom the regulatory oversight and jurisdiction of DSOD, once the existing EstatesReservoir is demolished and storage is converted to two smaller replacement tanks.sb09_001.doc 3-3.1 7/22/2009