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1 1y <br /> CA ® RA - <br /> 7 <br /> c�1 ti <br /> o Cambria evaluated water-level measurement data and prepared a groundwater contour <br /> map (Figure 2) Groundwater flows predominately to the southeast at an <br /> approximate hydraulic gradient of 0 02 <br /> o TPHg and benzene were not detected in any of the groundwater samples MTBE (by <br /> EPA Method 8020) was reported in wells RW-1, RW-2, MW-1, MW-3, VEW-1 <br /> through VEW-4 at concentrations ranging from 4 97 to 1,700 ppb The MTBE <br /> concentration in well MW-1 was confirmed by EPA Method 8260A at a <br /> concentration of 1,540 however the sample was analyzed outside of EPA <br /> recommended hold time A chemical concentration map is presented on Figure 2 <br /> Quarterly Sampling <br /> Groundwater samples were analyzed for total purgeable hydrocarbons as gasoline (TPHg) by <br /> EPA Method 8015 (Modified) and benzene, toluene, ethylbenzene, xylenes (BTEX), and <br /> methyl tertiary butyl ether (MTBE) by EPA Method 8020 and also by EPA Method 8260A <br /> in well MW-1 Well VEW-3 was also sampled and analyzed for halogenated volatile organics <br /> . by EPA Method 8010B (Table 1) <br /> Field monitoring data and chemical analytical data are presented in a summary table in <br /> Blaine's groundwater monitoring report (Appendix A) Additional groundwater analytical <br /> data is summarized on Table 1 <br /> Conclusions and Recommendations <br /> TPHg and benzene concentrations have been at low or non-detect levels at this site for <br /> several quarters MTBE detected at this site is suspected to be from an offsite source The <br /> subject site's service station was closed and the fuel USTs were removed in 1981, prior to <br /> wide spread use of MTBE in gasoline It is unlikely that MTBE detected beneath the subject <br /> site is from an onsite release, however, there is insufficient data at this time to prove that the <br /> MTBE is from an offsite source Cambria does not recommend continued monitoring and <br /> sampling at this site, but SJCPHS is requiring (June 27, 2000 SJCPHS letter) that we continue <br /> quarterly monitoring and sampling Quarterly monitoring and sampling will continue at this <br /> site on the established schedule <br /> 0821 2 <br />