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= Mr. Don McShane -` -2- 28 September 1993 <br /> 5. The ground water data show that total petroleum hydrocarbons (TPH) in the gasoline range <br /> were not detected in any of the five monitoring wells. However, the soil gas survey showed <br /> the presence of total volatile hydrocarbons in the C,-Cg range which is characteristic of <br /> gasoline. The ground water data also show the presence of benzene in all monitoring wells <br /> and ethylbenzene, toluene, and xylene in some wells, indicating the fuel was of gasoline origin <br /> since diesel typically does not have these components. TPH in the diesel range was detected <br /> in MWs 2, 3, and 4. No explanation was provided as to why TPHG was not detected in any <br /> of the wells. The ubiquitous presence of gasoline components and.the absence of TPHG in <br /> the monitoring wells suggest that gasoline leaks may have been occurred earlier than the diesel <br /> leaks. Also, as stated in the report, there could be other sources of the gasoline <br /> contamination. However, the report did not mention what these other sources could be. The Y <br /> extent of both types of contamination needs to be defined, as recommended in the report. <br /> 6. One of the conclusion states that the leak locations included the roadside dispenser, <br /> underground unleaded and regular gasoline lines, and the underground premix lines. Based on <br /> this statement, a diesel contamination source was not identified. As stated in Item 5 above, <br /> TPHD was detected in MWs 2, 3, and 4. The absence of TPHG and the presence of free <br /> product in MW 3 indicate that the free product has diesel characteristics. The source of the <br /> diesel contamination needs to be identified so it can be eliminated. <br /> 7. I concur with the recommendations presented in the report. <br /> By 26 October 1993, please submit a response to the above comments and'a work plan with a-time <br /> schedule for implementation of the recommendations. <br /> If you have any questions,. please call me at.(916) 255-3049. <br /> t II <br /> PHIL S. ISORENA <br /> Associate Engineer <br /> PSI:gs <br /> cc: Mr. Mike Infurna, San Joaquin County Public Health Services, Stockton <br /> Mr. Robert B. Sternfels, Reclamation District #548, Lodi <br /> Ms. Susan Gahry, Law/Crandall, Inc..,, San Rafael <br />