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Mr George Takemon Project OF90-002 04 <br /> March 8, 1996 <br /> Page 3 <br /> with a hydraulic gradient of 0 006 (see Figure 3) Groundwater elevations increased <br /> approximately 0 85 feet from the previous sampling event(August 1995) <br /> Analytical Methods and Results <br /> Groundwater samples collected from wells MW-9 through MW-11 and MW-14 were <br /> analyzed for TPHG using modified U S Environmental Protection Agency (USEPA) <br /> Method 5030/DHS LUFT and for BTEX using USEPA Method 5030/8020 The samples <br /> were analyzed at Columbia Analytical Services, Inc , in San Jose, California (California <br /> Department of Health Services Hazardous Waste Testing Laboratory Certification <br /> No 1426) Copies of the chain-of-custody records and laboratory analysis reports are <br /> presented in Appendix B Analytical results are summarized in Table 1 <br /> The results of laboratory analyses indicated that TPHG and BTEX were not detected in <br /> groundwater samples collected from wells MW-9 through MW-11, except for total <br /> xylenes which were detected in well MW-10 at a concentration of 0 8 parts per billion <br /> (ppb) TPHG and benzene were detected in the sample from well MW-14 at <br /> • concentrations of 300 and 2 7 ppb, respectively Concentrations of TPHG and benzene a*e <br /> shown on Figure 2 <br /> OPERA`'TON AND MAIN-ENANCE: FOUR`- QUAR 'ER "995 <br /> In April 1995, EMCON began overseeing the operation and maintenance of the <br /> remediation system The remediation system consists of an EI 250 thermal oxidizer fitted <br /> with a catalytic insert and rated at 250 cfm, and a vacuum blower The remediation system <br /> operates under a permit-to-operate issued by San Joaquin Valley Unified Air Pollution <br /> Control District (SJVUAPCD), No N-841-2-0 <br /> The blower extracts soil vapors from wells MW-13 and MW-14 Extracted soil vapors are <br /> combusted in either thermal or catalytic mode prior to discharge to the atmosphere The <br /> remediation system is currently operating in the catalytic mode An air sparge blower was <br /> installed and started up on June 19, 1995, to remediate dissolved hydrocarbons in the <br /> groundwater Air is being injected into well AS-1 at the rate of 5 cfm into the <br /> groundwater <br /> During the fourth quarter of 1995, a technician from EMCON conducted three monthly <br /> site visits During the site visits, system operational parameters were monitored (see field <br /> data sheets in Appendix C) <br /> SACW\PJOOF9010F900020 4FS-95klrns l <br />