ARCHIVED REPORTS_VAPOR INTRUSION SURVEY - SOIL GAS SAMPLING REPORT

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' from the nearby delta area and the deep water from the Port of Stockton and Ship Channel is causing poor quality saline water to move eastward beneath Stockton. ' Based on current Site investigations and data available from the surrounding LUFT sites, groundwater in the shallow aquifer beneath the site is found in un-confined conditions in four zones: • "Shallow"Zone water less than 37 feet bgs; • "A"Zone at approximately 37 to 57 feet bgs; • `B"Zone at approximately 70 to 90 feet bgs; and ' • "C"Zone at approximately 102 to 122 feet bgs. These zones likely do not represent distinct aquifers, but layers that are more permeable ' interbedded within less permeable discontinuous layers of clay, silt, clayey silt, and/or sandy silt. Based on groundwater-monitoring data, the direction of groundwater flow in the "A"-aquifer generally flows to the south. ' 1.5 Topography and Surface Water The elevation of the Site is approximately 10 feet above mean sea level (MSL) (USGS, 1987). The Site is generally flat and storm water drains to storm sewers located along Lincoln Street. ' Mormon Slough flows generally toward the west and passes within approximately 3,000 feet north of the Site before draining into the Stockton Deep Water Channel and San Joaquin River. Walker Slough flows generally toward the west and passes within approximately ' 7,000 feet south of the Site before draining into the San Joaquin River. The San Joaquin River and several of its major tributaries namely, the Stanislaus, Calaveras, and Mokelumne rivers drain the Eastern San Joaquin Subbasin. The San Joaquin River flows north into the Sacramento and San Joaquin Delta and discharges into San Francisco Bay (DWR, 2003). ' 1.6 Current Site Status The data obtained from the CPT investigation indicate that saturated soil is impacted by petroleum hydrocarbons beneath each of the areas investigated. The source of petroleum hydrocarbon impact appears to be both on and off site. The lateral extent of this impact has ' not been delineated. The vertical extent of impacts in saturated soil is less than 115 feet bgs over the entire Site. The lateral extent in groundwater beneath the Site including adjacent properties on Charter Way and Lincoln Street has yet to be defined, due to numerous on and off-site source areas. The vertical impacts in groundwater beneath the Site is expected to be less than 125 feet bgs based on soil samples collected in a clay layer consistently encountered at that depth. PSC presented the data obtained from the April 2008 CPT investigation to the CVRWQCB in the Subsurface Investigation Report, dated July 31, 2008. Vapor Intrusion Survey Soil Cas Sampling Report ' Prepared For:Sam Lee Bakery Croup,Inc. Prepared By:PSC Industrial Outsourcing,LP Sam Lee—Lincoln Street\2009_03_31-Soil Gas Sampling Report.doc March 31,2009 4 ,