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' EXECUTIVE SUMMARY <br /> ' The objective of the investigation was to further define the lateral extent of impacted sod and <br /> groundwater along the south and east walls of the parking garage site, so that property transfer <br /> decisions could be better evaluated On March 26, 2004, to achieve this objective, Ramage <br /> ' Environmental supervised the drilling of three on-site Geoprobe®direct-push sod borings (G-4, <br /> G-5 and G-6) From each of the three sod borings, two soil samples and one groundwater <br /> sample were collected for laboratory analysis Additionally, on March 24, 2004, the four existing <br /> ' groundwater monitoring wells (MW-1, MW-2, MW-3 and MW-4) were monitored and sampled <br /> In soil, the only petroleum compound detected was ethanol at a concentration of 0 018 <br /> ' milligrams per kilogram (mg/kg) in the sample collected at 25 feet below ground surface (bgs) at <br /> G-6 The low concentration of ethanol at G-6 is probably not significant, since the groundwater <br /> sample at G-6 did not contain ethanol Based on the cumulative sod sample analytical results, <br /> impacted sod appears to be concentrated beneath the former underground storage tanks (UST) <br /> and fuel dispenser system, and does not appear to have migrated beneath the south and east <br /> walls of the parking garage The extent of impacted soil remains undefined to the west of the <br /> garage, beneath the Hunter Street right-of-way <br /> In groundwater, low concentrations of gasoline compounds were detected in both soil borings <br /> located along the south wall of the parking garage (G-4 and G-5) The groundwater sample <br /> collected from G-4 contained 0 55 micrograms per Mer (µg11) of toluene, 0 79 µg11 of xylenes, 3 8 <br /> µg11 of MTBE, and 11 µgll of ethanol The groundwater sample collected from G-5 only <br /> ' contained 1 5 µg11 of MTBE These concentrations are below California Maximum Contaminant <br /> Levels The groundwater sample collected from G-6 along the east wall of the parking garage <br /> did not contain detectable concentrations of petroleum hydrocarbons Based on the cumulative <br /> groundwater sample analytical results, impacted groundwater also appears to be concentrated <br /> beneath the former UST and dispenser system, but does appear to have migrated to the south <br /> and southeast beneath the south wall of the parking garage The lateral extent of impacted <br /> groundwater appears to be defined to the east and north, but remains undefined to the west <br /> beneath the Hunter Street right-of-way <br /> ' Based on the results of this investigation, only low concentrations of petroleum hydrocarbons <br /> below water quality goals appear to have migrated to groundwater beneath the south wall of the <br /> parking garage Since groundwater sampling from a soil boring is a considered a screening <br /> ' method, Ramage Environmental recommends that groundwater conditions along the south and <br /> east walls of the parking garage be confirmed by installing groundwater monitoring wells <br /> Monitoring wells should also be installed to the west of the site to further define the lateral extent <br /> ' of impacted groundwater beneath the Hunter Street right-of-way Before considering the case <br /> for regulatory closure, the San Joaquin County Environmental Health Division will also likely <br /> require that the vertical extent of impacted groundwater also be investigated and defined <br /> ' 4 <br /> • <br />