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Rogar Huckins • - 3 - • October 24, 2011 <br /> Petroleum H drocarbon Constituent Concentration Water u /L WQOs <br /> Contaminant Soil m /k <br /> Maximum Latest Maximum Maatest <br /> (ug/L) <br /> TPH NA NA 230,000 160,000 5 <br /> Benzene NA NA 51,000 20,000 1 <br /> Toluene NA NA 110,000 34,000 150 <br /> Eth (benzene NA NA 16,000 5,000 300 <br /> Xylenes NA NA 25,200 25,200 1,750 <br /> MTBE NA NA 0.58 <1 5 <br /> TBA NA NA 370 <10 1211,200 <br /> 1,2-DCA NA NA 4,600 280 0.5 <br /> NA: Not Analyzed, Not Applicable or Data Not Available <br /> mg/kg: milligrams per kilogram, parts per million <br /> ug/L: micrograms per liter, parts per billion <br /> WQOs: Water Quality Objectives <br /> `According to GeoTracker,wells <br /> a California Department of Public Health Notification Level/Response Level <br /> Site Description <br /> The Site is located at 1201 South Center Street in Stockton, California. The Site is bounded by <br /> a residence to the west, West Jackson Road to the north and Turnpike Road to the southeast. <br /> The surrounding land use is mixed residential and commercial. <br /> Site History/Assessments <br /> In October 1994, soil contamination was identified during the removal of USTs. To date, 32 <br /> monitoring wells have been installed and monitored regularly. A Site map showing the location <br /> of the current USTs and monitoring wells s is provided at the end of this five year summary. <br /> Remediation Summary <br /> Free Product: No free product was documented throughout the life of this case <br /> • Soil Excavation: Unknown <br /> • In-Situ Soil Remediation: Soil vapor extraction, conducted from November 2009 through <br /> present removed approximately 22,659 pounds of TPHg. The rate of removal in <br /> September 2011 was approximately 2 pounds per day <br /> • Groundwater Remediation: No groundwater remediation has been conducted <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 is approximately 20 feet bgs and the <br /> groundwater gradient is easterly at approximately 0.005 feet per foot <br /> • Estimate of Hydrocarbon Mass in Soil: Prior to remediation, Advance <br /> Geoenviron mental, Inc. estimates that approximately 143,505 pounds of TPHg remains <br /> in site soil and 12,389 pounds of TPHg is dissolved in site groundwater. <br /> • Groundwater Trends: There are more than ten years of groundwater monitoring data for <br /> this Site. Benzene trends are shown below, source area (MW-1 and MW-4a) and down <br /> gradient (MW-7a) <br />