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I05 March 2002 .f AGE-NC Protect No 98-0426 Page 6 of 6 I 4.0. SUMMARY AND CONCLUSIONS Based on data collected during the installation of monitoring wells MW-4 and MW-5 on 18 , September 2001 and the advancement of soil borings P-7 to P-9 on 01 to 03 October 2001 to complement existing data at the site, AGE summarizes concludes •_ TPH-g, BTEX and fuel oxygenates were not detected in any of the soil samples analyzed • TPH-g was not detected in any of the water samples analyzed, BTEX compounds were detected in samples from borings P-7 and P-8, but the concentrations were well below California's Maximum Contaminant Levels(MCLs)for the compounds Benzene is the only petroleum hydrocarbon compound consistently reported above California's MCL at the site, from quarterly ground water samples collected from monitoring well MW-3 (see Table 2) • MTBE was detected in the ground water samples from boring B-8, located along the southern edge of the site, at concentrations of 12 µg/l at 30 feet bsg and'8 0 µg11 at 60 feet bsg, these concentrations are below California's Primary MCLS MTBE has not been detected in any soil samples collected at the site, and was not detected in the ground water sample at 60 feet bsg in boring B-7, located adjacent to MW-3 at the former UST area • With the possible exception of MTBE, which may have an off-site source, the vertical and lateral limits of hydrocarbons-impacted soil and ground water are defined at the site 5.0. RECOMMENDATIONS AGE believes that the practical vertical and lateral extent of hydrocarbons-impacted soil and ground water at the site have been defined AGE recommends continued quarterly monitoring of ground ' water monitoring wells for the remainder of the year At the end of this period,baring any increase in targeted analyte concentrations above California's MCLS,preparation of a closure report for this ' site may be appropriate ' 6.0. LIMITATIONS r Our professional services were performed using that degree of care and skill ordinarily exercised by ' environmental consultants practicing in~this or similar localities The findings were based mainly upon analytical results provided by an independent laboratory Evaluations of the geologic/hydro- geologic conditions at the site for the purpose of this investigation are made from a limited number ' of available data points(e g soil samples and ground water samples),and subsurface conditions may vary away from these data points No other warranty, expressed or implied, is made as to the professional interpretations, opinions and recommendations contained in this report ' Advanced GeoEnvironmental,Inc 1 ,