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Frontier Transportation 16 - 3 - October 25, 2011 <br /> Petroleum H drocarbon Constituent Concentration <br /> Contaminant Soil (mg/kg) Water (ug/L WQOs <br /> Maximum Latest Maximum Latest (ug/L) <br /> * <br /> (Apr 2011 <br /> TPHg NA NA 33,000 4,980 5 <br /> Benzene NA NA 2,300 25.6 1 <br /> Toluene NA NA 683 <0.5 150 <br /> Eth (benzene NA NA 3,800 12 300 <br /> Xylenes NA NA 6,500 1.6 1,750 <br /> MTBE NA NA 43,000 1,910 5 <br /> TBA NA NA 2,200 281 12/1,200a <br /> 1,2-DCA NA NA NA <0.5 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 425 Larch Road in Tracy, California and is an active retail gasoline station. <br /> The Site is bounded by businesses to the west and north, Industrial Way to the east and West <br /> Larch Road to the south. The surrounding land use is commercial. <br /> Site History/Assessments <br /> In August 1995, soil contamination was identified during the removal of USTs. To date, 28 <br /> monitoring wells have been installed and monitored regularly. A Site map showing the location <br /> of the former USTs, monitoring wells and groundwater gradient and MTBE concentration <br /> contours is provided at the end of this five year summary. <br /> Remediation Summary <br /> • Free Product: Free product noted in MW-2, MW-3r, MW-21, MW-22, MW-23, and <br /> MW-24, no free product noted since 2009. <br /> • Soil Excavation: Unknown <br /> • In-Situ Soil/ Groundwater Remediation: Dual phase extraction, pending <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 8 feet bgs and the groundwater <br /> gradient is southwest at approximately 0.0008 feet per foot <br /> • Groundwater Trends: There are more than 15 years of groundwater monitoring data for <br /> this Site. MTBE trends are shown below, source area (MW-21), near down gradient <br /> (MW-19) and far down gradient (MW-17) <br />