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3. CONTAMINANT ASSESSMENT <br /> 3- 1 PRIOR INVESTIGATIONS <br /> The site was closed after a product line failed in November 1985. <br /> The amDunt of fuel lost was unknown. Subsequent tank and product <br /> line removal was supervised by GTI. GTT installed two monitoring <br /> wells in January 1986 (MW1 , MW2, Figure 5 ) and an additional well <br /> r: <br /> in December 1986 (MW3 ). On the boring logs, GTI identified the <br /> materials immediately underlying the site as predominantly clays <br /> and sands, with lesser amounts of silt, silty clay, and silty <br /> t= sand with increasing depth. Two more monitoring wells (MW9, MW5 ) <br /> were installed by GTI in May 1987. <br /> 3.2 SOIL VAPOR CONTAMINANT ASSESSMENT <br /> On 23 and 24 November 1987, EA conducted an SVCA survey at the <br /> Stockton site. Soil gas samples were collected from depths of <br /> 5 approximately 20 feet at six locations on-site (V1-V6, Figure 5 ), <br /> and monitoring well headspace samples were taken from the <br /> five <br /> monitoring wells. A follow-up soil .gas survey for hydrocarbon. <br /> levels at shallow depths was conducted on 22 December. 1987. <br /> Shallow samples were collected from five locations. (V7-V11 , <br /> Figure 5) _ I <br /> r 3. 3 GROUNDWATER CHEMISTRY j <br /> y C rt <br /> ` The analytical chemistry results of groundwater monitorin are i <br /> g <br /> 2M t3 summarized for samples collected from November 1986 to January <br /> - <br /> "� <br /> 1989 (Table 2 ) , Throughout the samplirq period, the-Concentra-_ <br /> r <br /> tions;of petroleum h� - - ; - - -- - -- - <br /> a �,r r ydrocarbons are the highest. in MW3. This <br /> �s 7 <br /> well 'is located in the former. tank field area. Since monitoring <br /> a <br /> =4� <br /> began in November 1986, <br /> the=concentrations of petroleum hydro- <br /> carbons <br /> .carbons gin :groundwater beneath <br /> this site has <br /> ,TJX generally declined. <br /> The two most 'recent rounds of sampling show that benzene, f <br /> toluene, xylene, and total <br /> petroleum hydrocarbons were at or <br /> r ypt.` e25/7.1O5O/txt <br /> C 3 <br /> - <br /> * Y <br /> � s7 5r <br /> ss++yy b <br /> se's;``,r <br /> �.�a <br />