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KLEINFELDER Bright People.Right Solutions. j. Contribute to inundation by seiche, tsunami, or mudflow? 1NARRATIVE DISCUSSION Environmental Setting There are no surface water features on or near the project site. The nearest existing surface water feature is the Stockton Diverting Canal, approximately one mile to the northeast of the project site. The Stockton General Plan 2035 Background Report indicates that the project site is within the Stockton Channel watershed. The Stockton Channel is a manmade channel approximately 1.5 miles west of the project site which eventually discharges into the San Joaquin River. Drainage in the project vicinity is collected by existing City storm drainage systems; see Section C(16), Utilities and Service Systems, for more information. The project site is located within the San Joaquin Valley Groundwater Basin (California Department of Water Resources, 2003). The groundwater basin is characterized by relatively thick aquifers composed of unconsolidated alluvium with both unconfined and confined groundwater conditions. According to the San Joaquin County Public Works groundwater map, groundwater at the project site is from 20 to 30 feet below ground surface. Over the last 20 to 30 years, pumping for municipal and industrial uses in eastern San Joaquin County has exceeded the basin's sustainable yield and caused groundwater elevations to decline by 40 to 60 feet. The decline in groundwater elevations has created a cone of depression, allowing saltwater from the Delta region to intrude into the basin underlying the western portion of the COSMA, diminishing groundwater quality (City of Stockton, 2007). The Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map, effective October 2009, locates the proposed project in Zone X. Zone X is considered an "Other Flood Area" that includes areas of 500-year flooding; areas of 100-year flood with average depths of less than one foot or with drainage areas less than one square mile; and areas protected by levees from 100-year flood (FEMA#06077C0460F). The proposed project site, along with most of the Stockton area, is exposed to potential flooding from catastrophic failure to large dams located in the foothill areas to the east of the City. The risk associated with failure of these facilities is described as significant in the Stockton General Plan EIR, but this issue was judged to be acceptable when the General Plan was adopted. As the project site is located in a relatively flat area away from large bodies of water, it is not subject to inundation by seiche, tsunami, or mudflow. 121339/ST011 R226 3-37 October 14, 2011 Copyright 2011 Kleinfelder