ARCHIVED REPORTS_QUARTERLY GROUNDWATER MONITORING REPORT 1ST QUARTER-JANUARY 2010

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to 2.5 feet thick was occasionally encountered in the borings between approximately 17.5 and ' 28 feet. Based on recent borings, the majority of soil encountered beneath the Site is silt and clay. ' Layers of sand and silty sand were encountered at about 45-60 feet bgs, 70-90 feet bgs, and a thin layer around 115-120 feet bgs in the CPT investigation performed in April 2008. The layer encountered near the 85 foot depth has been described as sandy gravel. The boring for t CT-MW-9-120, drilled on the east side of the Site, confirms the sand layer at 115 feet bgs. However, the lack of sand layers from 87 feet bgs to 130 feet bgs in boring CT-MW-8-130 drilled on the west side of the Site indicates that this sand layer is laterally discontinuous. ' Based on geologic cross-sections prepared by consultants for the Dolly Madison, Chevron, and former Arco sites, the sandy gravel is present beneath the Chevron, and former Arco sites 1 at depths of approximately 60 to 90 feet bgs (Stratus, 2007; BBL, 2006; Delta, 2000). Sand and/or sandy gravel layers have been encountered at depths ranging from 105 to 120 feet bgs in borings located at the former Arco and former Texaco sites (Delta, 2000). 1.4. Local Hydrogeology Groundwater beneath the source area at the Site was first encountered at a depth of 22 feet ' bgs. Based on current site investigations and data available from the surrounding LUPI' sites, groundwater in the shallow aquifer beneath the Site is found in unconfined 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 do not represent distinct aquifers, but layers that are more permeable interbedded twithin 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. Data from newly installed deep wells and wells from the surrounding sites indicate groundwater in the deeper zones flow in a northeast to southeast direction. Sites in the vicinity of West Charter Way and South Lincoln Street generally ' exhibit a easterly flow direction for shallow groundwater. 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 St. ' 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 Quarterly Groundwater Monitoring Report First Quarter—January 1010 Prepared For:Sara Lee Bakery Group,Inc. Prepared By:PSC Industrial Outsourcing,LP Sara Lee—Lincoln Street\2010_01_QI-QMR(Lincoln).doc May 10,2010 4