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(1 1 %TC J , Laboratory results of the effluent vapor sample indicated destruction efficiency during the long- term test of approximately 92 percent for TPHg, approximately 98 percent for benzene, approximately 99 percent for toluene, and approximately 99 percent for ethylbenzene. C 4.0 DISCUSSION The soil vapor extraction pilot test yielded a radius of influence (ROI) of approximately 55 feet in well VE3. As shown in Section 3.2, approximately 7.0 pounds of TPHg were removed during the long term vapor extraction pilot test. During the long-tern vapor extraction test on well VE3, the vapor extraction rate appeared to equilibrate at approximately 62 cfm with a vacuum of t ' approximately 42 inches of water. Soil vapor extraction appears to be a viable method for remediating TPHg and BTEX impacted soil at the site. In ATC's experience, soil vapor extraction is also a moderately effective method for remediating TPHg, BTEX, and MTBE ' impacted groundwater. Soil vapor extraction is ineffective in preventing off-site migration of the r : impacted groundwater plume but this does not appear to be a concern at this time. ! 5.0 RECOMMENDATIONS 3 : It is ATC's opinion that vapor extraction is a viable remedial option for remediating impacted • soil at the site and ATC recommends enhancing soil vapor extraction with another alternative such as air sparging or groundwater extraction and treatment. If SJCEHD agrees with this recommendation, ATC will prepare an Interim Remediation Plan (IRP). ATC has recently submitted a workplan to SJCEHD to evaluate the vertical extent of petroleum hydrocarbon 1 ' impacted soil and groundwater. Once the vertical extent of petroleum hydrocarbon impacted soil and groundwater has been defined, ATC will submit a Final Remediation Plan (FRP). ATC will monitor wells MW 1 through MW 10 quarterly. t ' qi 878 ' IL �d f t a SAEnviromental\2529 Breports\rifs.doc 5 rr C.+