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M1 CA V BEUA <br /> Table 1 Site Conceptual Model,Shell-branded Service Station,2494 East Fremont Street,Stockton,California <br /> Site <br /> Addres 2494 East Fremont Street incident Number 98996181 <br /> City- Stockton, California Regulator San Joaquin County Environmental Health <br /> Department <br /> Item Evaluation Criteria Comments/Discussion <br /> 1 H drocarbon Source <br /> 1 1 Identify/Describe Release A specific fuel release incident has not been documented at this site <br /> Source and Volume (if known) However, soil data from the April 1996 tank& piping removal show the <br /> highest levels of petroleum hydrocarbons were detected in the <br /> northwestern dispenser area As such, the northwestern dispenser island <br /> will be considered the source area The release volume is unknown <br /> 1 2 Discuss Steps Taken to Stop The USTs and product piping were removed and replaced in April 1996 <br /> Release Fifteen cubic yards of soil were overexcavated from the UST pit, and 20 <br /> cubic yards of soil were overexcavated from the northestern dispenser <br /> island <br /> 2 Site Characterization <br /> 21 Current Site Use/Status The site is currently an active Shell-branded service station retailing three <br /> ® grades of gasoline Diesel fuel is not sold at this facility <br /> 2 2 Sod Definition Status The lateral and vertical extents of gasoling constituents in soil have been <br /> defined around the USTs by the soil samples collected when the tank <br /> was removed and by boring SB-1 The lateral and vertical extents of <br /> gasoline constituents in sod have been defined in the vicinity of the <br /> northwestern dispenser island by borings SB-4, SB-5, SB-6, and SB-8 <br /> Fuel oxygenates have not been detected in soil at this site 1,2-DCA has <br /> been detected in one soil sample(SB-4 @ 70 fbg) at a concentration of <br /> 0 141 ppm <br /> 2 3 Separate-Phase Hydrocarbon Separate phase hydrocarbons were detected in well S-1 during the first <br /> Definition Status sampling event (11-May-98) at a thickness of 0 01 foot Separate phase <br /> hydrocarbon has not been detected in this well since then, nor in any <br /> other well <br /> 2 4 Groundwater Definition Status Shallow groundwater definition appears to be complete for BTEX, with <br /> (BTEX) well S-1 generally being the only well to show elevated BTEX <br /> concentrations Well S-4, located downgradient of S-1, occasionally has <br /> low level BTEX detections The delineation of BTEX in deep <br /> groundwater beneath the site has been achieved by borings SB-4 <br /> (vertical delineation), and borings SB-7, SB-9, SB-11 through SB-16, SB- <br /> 18 and wells S-3-84 and S-4-83 <br /> 2 5 BTEX Plume Stability and BTEX concentrations are showing a stable or decreasing trend in well S- <br /> Concentration Trends 1 Wells S-2, S-3, and S-4 typically contain BTEX concentrations below <br /> the detection limit and therefore cannot be used for trend analysis The <br /> deep wells have only been sampled twice since they were installed and <br /> therefore cannot be use for trend analysis <br /> i <br /> 0955 Page 1 of 4 Date Modified 8/14/2003 <br />