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Thrifty Oil Co. Station #172
<br /> Paget
<br /> towards pumping wells MW-10 and MW-11
<br /> Quarterly Groundwater Sampling
<br /> As part of the groundwater-momtonng program, groundwater samples were obtained from
<br /> monitoring wells MW-3 through MW-11 (except MW-8, which was abandoned) Groundwater
<br /> samples were obtained by EMC on May 21, 2003, and delivered in a chilled state, in an ice chest,
<br /> following strict Chain-of-Custody procedures to a state certified laboratory These samples were
<br /> analyzed for volatile aromatic compounds benzene, toluene, ethylbenzene, and xylenes (BTEX) and
<br /> selected oxygenates (including MTBE)by EPA method 8260B, and total petroleum hydrocarbons
<br /> as gasoline(TPH-g)by EPA method 8015M Ethanol and methanol were analyzed by method D285
<br /> TPH-g, BTEX, and MTBE concentrations appear in Table 1, while historical oxygenate and alcohol
<br /> results are presented in Table 2 Copies of groundwater laboratory reports and chain-of-custody
<br /> documents are included in Appendix B The TPH-g, benzene, and MTBE isoconcentration maps
<br /> are presented as Figures 3,4, and 5, respectively The highest concentrations of TPH-g, benzene,
<br /> and MTBE in groundwater were found in monitoring well MW-11 (61,700 ug/L, 9,820 ug/L, and
<br /> 4,500 ug/L, respectively) The remaining site wells have very low to non-detectable constituent
<br /> concentrations
<br /> Since the third quarter of 1997, Thrifty has analyzed for oxygenates di-isopropyl ether(DIPE), ethyl-
<br /> tert butyl ether (ETBE), tert-amyl methyl ether (TAME), and tert-butanol (TBA), and MTBE by
<br /> method 8260B The alcohols (ethanol and methanol) were analyzed by ASTM standard D285 The
<br /> County of San Joaquin Public Health Services (CSJPHS) requested these analyses Laboratory
<br /> results indicate no alcohols or oxygenates (besides MTBE) were detected above the laboratory
<br /> detection limit, with the exception of 365J ug/L TBA in well MW-11 It has been over one year
<br /> without detecting the alcohol constituents in groundwater samples Therefore, Thrifty respectfully
<br /> requests for cessation of the requirements for methanol and ethanol analysis at this site
<br /> Remediation Status
<br /> Vapor Extraction System
<br /> On April 26, 2001, a new Baker Furnace Then-nal Oxidizer Unit was placed into operation with the
<br /> hour meter reading at zero Presently, the remediation system is connected to soil vapor extraction
<br /> wells (VW-1, VW-2 (A,B),VW-3, VW-4 (A,B,C), VW-5 (A,B,C), and VW-6 (A,B,C)) The vapor
<br /> wells operating during the second quarter of 2003 were VW-3, VW-5A, VW-5B (50%), and VW-5C
<br /> (25%) During the second quarter of 2003, the soil vapor extraction unit (VEU) operated
<br /> approximately 1,953 hours for a cumulative total of 16,325 hours Approximately 6,837 pounds of
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