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15135 Eight Mile Road -4- 1 October 2018 <br /> Stockton, San Joaquin County <br /> ether(TAME), and ethylene dibromide (EDB) were detected in isolated areas of the Site in low <br /> concentrations; the maximum concentrations of these constituents detected in shallow soil are <br /> shown in Table 2. Concentrations of EDB detected in three soil samples shallower than five feet bgs <br /> exceed the SFRWQCB ESL for this constituent; however, this shallow soil is contained beneath a <br /> concrete pad which inhibits exposure. <br /> Table 1 —Current and Historical Maximum Shallow Soil Sampling Results <br /> Between 0 and 10 Feet bgs and Corresponding LTCP*Screening Levels and Environmental <br /> ScreeningLevels** ESL and concentrations in milligrams per kilogram [mg/kg] <br /> Depth TPHd TPHg Benzene Toluene Ethyl- Total MTBE , Naphtha <br /> (feet bgs) benzene Xylenes -lene <br /> Historical^ 0 to 5 9,000 4,000 64 530 200 1090 94 N/A <br /> (2002/2003) <br /> Historical^ 5 to 10 <10 2,000 58 0.011 0.014 0.28 0.089 N/A <br /> (2002/2003) <br /> Current"^ 0 to 5 N/A 369 0.42 N/A 6.89 N/A N/A <0.002 <br /> (2016) <br /> Current^^ 5 to 10 N/A 287 11.6 N/A 10.2 N/A N/A <0.002 <br /> (2016) <br /> LTCP* 0 to 5 No No 1.9/8.2 No 21/89 No No 9,7/45 <br /> (res/com) Standard StandardStandard Standard Standard <br /> LTP <br /> No No No No No <br /> (es Com*) 5 to 10 Standard Standard 2.8/12 Standard 32/134 Standard Standard 97/45 <br /> ESL"' 0 to 10 230/ 740/ 0.23/1.0 970/ 5.1/22 560/ 42/180 3.3/14 <br /> (res/com) 1,100 3,900 4,600 2,400 <br /> bgs-below ground surface;*Low-Threat Closure Policy Table 1-Concentrations of Petroleum Constituents in Soil That Will Have No Significant <br /> Risk of Adversely Affecting Human Health(Residential/Commercial); **San Francisco Bay Regional Water Quality Control Board 2016 <br /> Environmental Screening Levels for shallow soil/groundwater as potential drinking water source(Residential/Commercial);TPHd-total <br /> petroleum hydrocarbons as diesel;TPHg-total petroleum hydrocarbons as gasoline; MTBE-methyl tertiary-butyl ether;^Soil sample locations <br /> MW6-5, B16-1,B16-4 and B16-8;^^Soil sampling locations CB2-2 and CB2-5; NIA-Not Analyzed <br /> Table 2 — Maximum Concentrations of Select Gasoline Additives Detected in Soil <br /> Between 0 and 10 Feet bgs with Corresponding Environmental Screening Levels* <br /> concentrations in milli rams per kilogram [mg/kg]) <br /> ESL* <br /> (res/com) MW6-5 MW7-5 B15-1 B16-1 B16-4 B16-8 B17-3 B17-9.5 B-24-10 <br /> Depth 0 to 10 5 5 1 1 4 8 <br /> feet bgs) <br /> 3 9.5 10 <br /> TAME NO Standard 2.2 0.12 <0.01 <0V <0,01 <n.n1 <0.01 0.12 <0.01 <br /> TBA No <10 0.3 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 9.8 <br /> _ Standard _ <br /> EDB 0.0361 <0.5 <0.01 0.24 11 9 0.045 0.013 3.5 <0.005 <br /> 0.16 <br /> bgs-below ground surface:*San Francisco Bay Regional Water Quality Control Board 2016 Environmental Screening Levels for shallow soil/ <br /> groundwater as potential drinking water source(Residential/Commercial);TBA-Tertiary-butyl alcohol;TAME-tertiary-amyl methyl ether; <br /> EDB-ethylene dibromide <br /> Groundwater— Groundwater monitoring began at the Site in September 1997. Between 2002 and <br /> 2004, H&H detected total petroleum hydrocarbons as gasoline (TPHg) in monitoring well MW-2 at <br /> concentrations which are indicative of non-aqueous phase hydrocarbons (i.e., "free product"). <br /> Following the 2007 vandalism and petroleum release from one of the ASTs, H&H observed <br />