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a 02 April 1998 • AGE-NC Project No 95-0111 , ' Page 4 of 4 r 4 2 RECOMMENDATIONS 1 The results of more than two years of ground water monitoring has shown that the ground water flow ' direction has been consistently toward the north-northeast to northeast On two occasions,the ground water flow direction on the southern portion of the property has been toward the southwest Over two years of monitoring, MW-6, the down-gradient well has contained detectable concentrations of ' TPH-d on only two occasions (6196 and 9196) and detectable concentrations of MTBE on only one occasion (6/96), other analytes have not been detected This data demonstrates that the plume of impacted ground water is stable and is not actively migrating ' The quantified concentrations of detected analytes in samples collected from wells in the UST area (MW-1 and MW2) and immediately down-gradient of the UST area (MW-4 and MW-5) have ' fluctuated over time Concentrations of toluene, ethylbenzene and xylenes have not ever exceeded state maximum contaminant levels (MCLs) established by the state of California for these r compounds in drinking water MCLs have not been established for TPH-g or TPH-d The concentrations of TPH-g and TPH-d fluctuate over a broad range, but appear to be dechrung overall r� The concentrations of benzene and MTBE exceed the state MCL and action level, respectively, for these compounds Although these compounds exceed the state MCL and action level, in view of the plume stability, AGE believes it is time to determine suitability of the site foz closure To prepare ' for a closure request, AGE recommends • Completion of a well and receptor survey in the area around the subject property, rReview files of nearby properties that have recently been assessed to incorporate their data into our site model, • Performance of a health-risk based assessment for the site, and r . • Continued quarterly monitoring of ground water on the site r f r 50. LIMITATIONS f Our professional services were performed using that degree of care and skill ordinarily exercised by r environmental consultants practicing in this or similar localities The findings.were based upon analytical results provided by an independent laboratory Evaluations of the geologic/hydrogeologic conditions at the site-for the purpose of this investigation are made from a limited number of ravailable data points (i e ground water monitoring well samples) and subsurface conditions may vary away from these data points No other warranty, expressed or implied, is made as to the professional recommendations contained in this report rAdvanced GeoEnvironmental Inc r -