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Sara Lee Baking Co. v - 3 - %.041 August 16, 2011 <br />Site Description <br />The Site is located at 2651 South Airport Way in Stockton, California and is an active <br />manufacturing business. The Site is bounded by agricultural fields to the west and south, a <br />business to the north and South Airport Road to the east. The surrounding land use is mixed <br />residential and commercial. <br />Site History/Assessments <br />In December 1986, USTs failed a tank tightness test. To date, 21 monitoring wells have been <br />installed and monitored regularly. A Site map showing the location of the former USTs, <br />monitoring wells and groundwater level contours is provided at the end of this five year <br />summary. Benzene iso -concentration map shown at the end of this review. <br />Remediation Summary <br />• Free Product: No free product was documented throughout the life of this case. <br />• Soil Excavation: An estimated 450 cubic yards of impacted soil were removed and <br />disposed offsite in 1987 <br />• In -Situ Soil/ Groundwater Remediation: Soil vapor extraction and air sparging, <br />conducted from June 2000 through December 2002 removed approximately <br />1,000 pounds of TPHg. <br />• Groundwater Remediation: In-situ chemical oxidation, ISCO pilot test <br />General Site Conditions <br />• Geology and Hydrogeology: The Site is underlain by interbedded and intermixed sand, <br />silt and clay. The depth to groundwater varies seasonally between 35 to 39 feet bgs and <br />the groundwater gradient is east southeast at approximately 0.002 feet/foot. The <br />nearest surface water body is Duck Creek, located approximately 900 feet south of the <br />site. <br />• Estimate of Hydrocarbon Mass in Soil: PSC Industrial Outsourcing (consultant) <br />estimated that approximately 494 kg of TPHg remains dissolved in groundwater and <br />3900 kg in soil. <br />• Groundwater Trends: There are more than 14 years of groundwater monitoring data for <br />this Site. Benzene trends are shown below, source area (MW -1 and PZ -2) and down <br />gradient (MW -7) <br />loco <br />e6o <br />eao <br />>oo <br />600' <br />500 <br />N1 <00 <br />300 <br />3W <br />100q <br />10 <br />BENZENE Resu is for MW -1 <br />..cv BENZENE --- Trend <br />l <br />