SITE INFORMATION AND CORRESPONDENCE

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Shell Oil Sites Page 2 1267 CounM Club Stockton EHD does not consider the extent of the waste oil impact to soil and groundwater defined. The work plan recently submitted has not been approved. An addendum to that work plan will be prepared that addresses EHD's concerns with the waste oil investigation and provides investigation down gradient(northeast) of the petroleum fuel contaminant plume. 2575 CounM Club Stockton The current proposal for replacement of monitoring well MW5 will not provide the information required to delineate the extent of the contaminant plume. Additional ground water investigation is needed in areas where analytical results of soil samples from borings showed the soil to be highly contaminated. A work plan addendum is to be submitted that proposes placement and construction of monitoring wells that will provide delineation of the contaminant plume. 2320 El Dorado Street Stockton EHD agreed with Cambria that contaminants might be migrating across El Dorado Street from the site at 2315 El Dorado Street. It is unknown if the contamination detected in the monitoring wells at the Shell station is the result of the residual soil contamination from the three UST's that were removed in 1990 (no further action required letter provided in 1991),a result of new release(s) between 1991 and the present, or migration of contaminants from the 2315 El Dorado Street site. EHD requested that an SCM be included in the next quarterly monitoring report (QMR), or by the 3rd quarter 2005 QMR, that would discuss the contaminant plumes at both sites. EHD agreed that the enactment of the approved cone penetrometer (CPT)work plan dated October 4, 2004 should be postponed at this time. Shell agreed to analyze for trichloroethene (TCE) and tetrachloroethene (PCE) in water samples from MW-3 and MW-4 the next quarter(3rd QMR) since both contaminants were detected in the 4th quarter 2004 monitoring event. EHD may request additional quarterly sampling of TCE and PCE in two or more monitoring wells in the future. Cambria suggested that the responsible party of 2315 El Dorado Street should also include analyses for TCE and PCE on their water samples. EHD encourages Shell to coordinate sampling and testing with the responsible party for 2315 El Dorado Street. As agreed to at the meeting,EHD has completed a cursory review of the history and investigation of the former waste oil underground storage tank (UST) tank at the 2315 El Dorado Street. In April 1987,a 200-gallon waste oil UST was removed from the site. Analytical results of the soil sample collected beneath the UST were non-detect (ND) for TCE and 1.6 micrograms per kilograms (ug/kg) of PCE. In October 1993 multiple soil samples were collected from 3 soil borings to 30 feet below surface grade (bsg) and 1 soil boring to 36 feet bsg that were installed next to the former UST. Analytical results of all the samples were ND for PCE and TCE. Analytical results of a ground water sample from monitoring well MW-1 installed next to the former UST in September 1994 were also ND for PCE and TCE. EHD also reviewed our Shell station UST file and found that Shell originally reported a 550 gallon waste oil UST to be at the site but when EHD staff inspected the site in 1986 it was stated that the UST had been removed prior to 1984 so there is no soil data on the Shell waste oil UST. The file did have soil sample results from the UST system removal in,July 1990 and soil samples SS-1,5,7, 10, 11 and 12 all had detections of PCE in the soil samples collected. Please be aware that the information presented in this letter is based on a cursory review. EHD recommends you perform a file review of your own.