AgdaPkt 2010-01-25 clsd and regular

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6.2A Page 53 imported water supply. Pipeline failure could come in the form of a pipe bursting or as a result of a major seismic event. The u.s. Geological Survey has estimated a 62 percent probability of at least one magnitude 6.7 or greater earthquake between 2003 and 2032. The failure of one or more pipelines would result in the loss of potable water supply to both residential and commercial customers, resulting in major water shortages. Such shortages could require water rationing and the importing of water until the repairs are completed. The Commission rejects this alternative as infeasible because it fails to meet the SFPUC's Project objectives for the reasons discussed below: The No Project Variant would not be consistent with SFPUC) s mission of serving San Francisco and its Bay Area customers with reliable, high quality, and affordable water. Existing facilities were constructed as early as the 1920s and at the time were not sized t.o meet water supply needs through the year 2018, which is the SFPUC's planning horizon for the WSIP. While planned repairs and improvements could help extend BDPL Nos. 1 and 2, these existing facilities do not and would not reliably or adequately serve current and future populations, based on current per- capita levels of use and the potential for a prolonged drought. For instance, jurisdictions served by the SFPUC, specifically the cities of Foster City and San Mateo, have adopted Statements of Overriding Considerations for their general plans because water supply constraints were considered to be significant and unavoidable impacts in approving new development. Additionally, the No Project Variant would not provide sufficient redundancy to ensure uninterrupted water delivery ifboth planned and unplanned outages occur simultaneously. Thus, one Project objective is to contribute to meeting the estimated average annual demand of up to 300 mgd by 2030 under the conditions of one planned shutdown of a major facility for maintenance concurrent with one unplanned facility outage caused by a natural disaster, emergency, or facility failure or upset. Similar to the No Project Alternative, the No Project Variant would not address the need to ensure continuation of service by providing seismic reliability, flexibility, capacity, and redundancy. These system attributes are needed to address required shutdowns for inspection, repair, rehabilitation, or replacement of pipeline sections, as well as reliable replenishment of local reservoirs. Alternative 3: Northern Alignment Alternative This alternative would cross San Francisco Bay by utilizing the existing Dumbarton and Ravenswood piers on either side of the Bay. It would not include the Bay Tunnel associated with the proposed Project. The Northern Alignment Alternative would follow the existing right of way ofBDPL Nos. 1 and 2, but would then follow local streets to reach the Dumbarton and Ravenswood Piers. The pipeline would rest on top of the former road surfaces of the piers. The pipeline's middle segment would extend between the piers by placing the pipeline within a trench on the Bay's bottom or by constructing shafts and a tunnel. Tunnel construction between the piers could require constructing large earthen cofferdams at the ends of the piers in San Francisco Bay to create a work area. The construction contractor would use either barges and/or the piers as staging areas. Because the Northern Alignment Alternative would rely on the continued use of BDPL Nos. 1 and 2 across San Francisco Bay, these facilities would not be decommissioned under this alternative because the new pipeline partially supported by the piers would not have adequate capacity to convey all of the water from BDPL Nos. 1 and 2. The SFPUC determined, through engineering studies completed by G&E Engineering Systems and OPAC Consulting Engineers, that BDPL Nos. 1 and 2, the two oldest pipelines, would require several repairs and seismic upgrades. In addition, photographic investigations show that the interior pipeline walls in several areas of BDPL No. 1 have suffered advanced pitting, or narrowing of the walls, resulting in structural 43