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5 -4 Dissolved Hydrocarbons in Groundwater <br /> Based on analytical results from groundwater samples collected during investigations it appears <br /> ' that groundwater has not been significantly impacted No BTEX constituents or TPHg have <br /> been detected in any samples collected from site monitoring wells since the initial sampling of <br /> MWI on March 4, 1992 TPHd was detected only in wells MW-3 and MW-4 in October 1993, <br /> and reported as non-diesel mix & discrete peaks (Table 2) <br /> 6.0 INTERIM REMEDIATION AND EVALUATION <br /> 6_1 Vapor Extraction Test <br /> RESNA performed a vapor extraction test at the subject site on October 22, 1993, to evaluate <br /> the use of vapor extraction as a method for remediating vadose soil Field results indicated air <br /> flow rates ranging from 105 to 113 cubic feet per minute could be extracted from each well VW- <br /> 1 through VW-3 at an applied vacuum of 30 inches water column Air samples contained TPHg <br /> concentrations ranging from non-detectable to 230 mg/m3 and benzene concentrations ranging <br /> from non-detectable to 0 075 mg/m3 The observed radius of influence exceeded 30 feet (Plate <br /> ' 6) Based upon test data RESNA concluded that vapor extraction is a feasible technology to <br /> remove gasoline hydrocarbons from beneath the site The monitoring data and laboratory <br /> ' analytical results are contained in Tables 3 and 4, respectively, and in "Summary of Additional <br /> Site Assessment and Remedial Investigation Results, " (RESNA, March 1994) <br /> 66.2 Excavation Activities <br /> ' On January 4, 1994, approximately 160 cubic yards of impacted soil was excavated from the <br /> vicinity of the former underground diesel storage tanks Excavation was limited along the north <br /> ' side of the property due to the presence of California Street Confirmation soil samples <br /> collected from the sidewalls and floor of the excavation indicated that no BTEX constituents <br /> ' were present in any of the samples Low levels of TPHd were reported in samples collected <br /> from the floor, east wall and south wall of the excavation TPHd was detected at 20,000 ppm <br /> ' in the sample collected from the north wall of the excavation beneath California Street A <br /> second sample collected from the north wall on March 17, 1994 (EP-HBEW-8) confirmed the <br /> 150047\PXMRTS%CAP 0694 FNL 7 <br />