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August 6, 1993 <br /> Page 2 <br /> . between February and April 1988 During station demolition, two 10,000-gallon <br /> underground gasoline tanks were removed from a common excavation along with a <br /> separate 550-gallon waste oil tank The former tank locations, along with the <br /> product islands and station building, are shown on Figure 2. <br /> During tank removal, 1,100 cubic yards of soil were removed from the site Soils <br /> within the tank excavation were removed to a depth of 30 feet Soils at the base of <br /> the excavation contained a maximum of 18 parts per million (ppm) total petroleum <br /> hydrocarbons calculated as gasoline (TPH-g) and 1.7 ppm benzene Soils beneath <br /> the product lines were found to have a maximum TPH-g concentration of 6 ppm <br /> No benzene was detected in the product line samples No hydrocarbons were <br /> detected beneath the waste oil tank. <br /> Kleinfelder, Inc installed five soil bonngs (KB1 through KB5) at the site in <br /> January 1988 These borings were installed around the former tank complex, adja- <br /> cent to the product islands, and adjacent to the former waste oil tank (Figure 2) <br /> Between June 1988 and February 1992, Applied and Resna (formerly Applied <br /> Geosystems) installed a total of seven monitoring wells (MW-1 through MW-7) <br /> and three soil vapor extraction wells (VW-1 through VW-3) Monitoring <br /> Wells MW-1, MW-2, MW-3, and MW-6 are located on site and Wells MW-4, <br /> . MW-5, and MW-7 are located northeast (downgradient) of the site The soil vapor <br /> extraction wells are located in the vicinity of the former product islands. <br /> Resna/Applied also installed 11 soil borings (B-1 through B-11) Most of these <br /> borings were converted to either groundwater monitoring wells or soil vapor <br /> extraction wells The monitoring well and soil vapor extraction well locations are <br /> shown on Figure 2 <br /> A soil vapor extraction test was performed in March 1992 by Resna The results of <br /> this test show that with a wellhead flow rate of 43 cubic feet per minute (cfm), an <br /> effective radius of influence of approximately 25 feet can be achieved for one <br /> vapor extraction well These results were documented in a report by Resna dated <br /> January 4, 1993 <br /> SOIL CONDITIONS <br /> The site is underlain by primarily fine-grained deposits consisting of mterlayered <br /> clays and silts to an approximate depth of 50 feet Some surficial silty sands occur <br /> to a depth of approximately 25 feet Occasional interlayered silty sands (up to <br /> 50 feet thick) were found to the total depth explored (Figure 3) <br /> 3104001\WORKPLN <br />