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h lrU <br /> ERI 205513 QSRIO Tom 76 Seirvicr,&atton 5896. Stpckton.Califomia <br /> • TPPHg and benzene were not detected at or above laboratory method detection limits in <br /> groundwater samples collected from the groundwater monitoring wells except for 54 ppb <br /> TPPHg in off-site cluster well MW91 However, the laboratory notes characterized the <br /> TPPHg as an unidentified hydrocarbon within the TPPHg range Additionally, detection <br /> limits were elevated for groundwater samples collected from wells MW2 and MW3 <br /> • Diesel-range hydrocarbons were not detected at or above laboratory method detection limits <br /> in groundwater samples collected from wells MW1, MW2, MW4S, MW5D, MW5S, <br /> MW6D, MW7D, MW7S, MW81, MW9S, MW9I, and MW10S through MW10D Diesel- <br /> range hydrocarbons were detected in the remaining wells at concentrations ranging from 50 <br /> ppb to 73 ppb However, diesel-range hydrocarbons were not detected at or above <br /> laboratory method detection lirmts in these wells once the samples were subjected to a silica <br /> gel clean up <br /> • MTBE was not detected at or above laboratory method detection linvts in groundwater <br /> samples collected from wells MW5D, MW7D, MW7S, MW8S, and MW9S through <br /> MW9D MTBE was detected in the remaining wells(excluding well MW8I) at <br /> concentrations ranging from 3 0 ppb to 20,000 ppb using EPA Method 8020 (2 6 ppb to <br /> 17,000 ppb [including well MW81] using EPA Method 8260) <br /> + Oxygenated compounds ethanol, tertiary butanol, di-isopropyl ether (DIPE), ethyl <br /> tertiary butyl ether (ETBE), and tertiary amyl methyl ether (TAME) were not detected at <br /> or above laboratory method detection limits in the groundwater monitoring well samples <br /> i <br /> FOURTH QUARTER 1999 ACIVITIES <br /> The following activities are proposed to be completed during fourth quarter 1999 <br /> • ERI will submit a report summarizing the results of the VET <br /> • Tosco will continue quarterly groundwater monitoring and sampling at the subject site <br /> • ERI and Tosco will continue to conduct a comprehensive review of the data acquired during <br /> previous work The results will be presented to the County in quarterly reports, which describe the <br /> status of the proposed work by the dates established by the County <br /> ERI recommends signed copies of this summary report be forwarded to the following <br /> Mr Ronald Rowe, Sr <br /> Site Mitigation Unit <br /> San Joaquin County Public Health Services <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, California 95202 <br /> 5 <br />