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Former Chevron Station #9-8662 - 3 - 19 March 2019 <br />575 W. Grant Line Rd <br />Tracy, San Joaquin County <br />Table 3 - Most Recent Groundwater Analytical Results /L <br />Well Zone <br />Screen <br />Interval <br />Range <br />TPHg TPHd B T E X MTBE <br />MW-1 <br />Shallow 5-20 <br /><100 <110 <1 <1 <1 <1 <1 <br />MW-2 <100 <110 <1 <1 <1 <1 1.0 <br />MW-3 220 <110 <1 <1 <1 <1 3.0 <br />MW-4 <100 <110 <1 <1 <1 <1 <1 <br />MW-6A <100 <110 <1 <1 <1 <1 <1 <br />MW-7 220 65 <1 <1 <1 <1 <1 <br />MW-5 Deep 41.5-50 <100 <110 <1 <1 <1 <1 <1 <br />MW-6B <100 <110 <1 <1 <1 <1 <1 <br />Water Quality Objectives 5 56 1 150 300 1,750 5 <br />TPHg=total petroleum hydrocarbons as gasoline TPHd=TPH as diesel BTEX=benzene, toluene, ethylbenzene, xylenes, <br />MTBE=methyl tert butyl ether <br />Soil Gas - The highest historical hydrocarbon concentrations detected in soil gas beneath the <br />Site are shown in Table 4. <br />Table 4 - Maximum Petroleum Hydrocarbons in Soil Gas <br />concentrations in micro rams er cubic meter im3 <br />TPHg Benzene Toluene Ethyl- <br />benzene MTBE Naph- <br />thalene <br />OxygenXylenes Range (`)/0) <br />22,000,000 26,000 15,000 120,000 67,000 100,000 <22,000 1.0-16 <br />TPHg=total petroleum hydrocarbons as gasoline; MTBE=methyl tert butyl ether, <br />GENERAL SITE CONDITIONS <br />Soils encountered during Site investigations are primarily silty clay and discontinuous lenses of <br />silt or clayey silt containing occasional, varying amounts of fine-grained sand, to the maximum <br />depth investigated of 50 feet below ground surface (bgs). Depth to groundwater has ranged <br />from 4.78 to 8.92 feet bgs and historically flowed to the northwest. <br />The nearest surface water bodies, industrial waste ponds, are located approximately 1.3 miles <br />northeast of and in the cross-gradient groundwater flow direction from the Site. Another surface <br />water body, the Sugar Cut extension of Tom Paine Slough, is approximately 1.5 miles northeast <br />of the Site. The nearest municipal/domestic well is located approximately 1,200 feet northeast <br />of the Site. <br />All remaining groundwater monitoring, remediation, and soil gas wells were properly abandoned <br />between 23 and 31 January 2019. <br />LOW-THREAT UST CLOSURE POLICY EVALUATION <br />GHD concludes and Water Board staff concurs that the Site meets the State Water Resources <br />Control Board's LTCP's criteria for closure.