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1 Job No 4780201 • • 8 <br /> ' 6.0 CONCLUSIONS AND RECOMMENDATIONS <br /> ' The results of sampling conducted during this study indicate that the soil and <br /> groundwater in the immediate downgradient proximity of the former 1,000- <br /> gallon diesel and 2,000-gallon gasoline tanks has been impacted by diesel, <br /> gasoline, and related constituents. Although elevated levels of gasoline were <br /> ' detected in the soil at depths extending from 20-to-30 feet, groundwater <br /> ' impact does not appear to be severe. Floating product was not detected in <br /> well MW-1, and detected Benzene levels in the well are less than 50 ppb. This <br /> ' level of Benzene, however, is still above the 1 ppb MCL established by the <br /> State of California, Office of Drinking water. The 1 ppb MCL is the typical <br /> ' target cleanup level referred to by the local overseeing agency. <br /> ' Although the aerial extent of soil and groundwater impact at the site has not <br /> yet been determined, it appears that soil and groundwater impact in the <br /> ' immediate area of the two former tanks situated between the buildings is <br /> moderate rather than severe. Based on our knowledge of current local and <br /> ' state regulatory requirements governing fuel leak sites, it is our opinion that <br /> additional soil and groundwater study will be required within the boundaries of <br /> ' the site, as well as at off-site locations to the west beneath South American <br /> Street. However, based on the depth of elevated levels of TPHg in the soil, and <br /> ' the absence of floating product in well MW-1 , there is only a low potential that <br /> ' soil and groundwater remediation would be required in relation to these two <br /> former tanks. It is more likely that regulatory requirements will consist of the <br /> ' installation of up to several additional wells and the implementation of a <br /> groundwater monitoring program to evaluate the attenuation of contaminants in <br /> ' the groundwater over time. Such a monitoring program may extend over a <br /> period of several years and will likely involve quarterly samplings of all, or some <br /> ' of, the wells necessary to delineate the groundwater contaminant plume. <br /> ' EZC, Inc. September 18, 1997 <br />