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S E C 0 R Mr Harlin Knoll March 30, 2006 Page 4 hydrocarbon constituents were reported in the certified laboratory analytical reports for groundwater samples collected from monitoring well MW-68 Groundwater monitoring well MW-7 Is located behind the station building, downgradient and northeast of the former UST area and dispenser Islands The constituents TPI-Ig, benzene, and MtBE continue to remain below their MDLs, while TPHd concentrations have decreased from the data reported in the previous quarter Based on the data presented above, it appears that the plume beneath the site experiences fluctuations of TPHd, TPI-Ig, benzene, and MtBE In some cases, when the concentration of TPHg decreases the corresponding concentration of TPHd Increases and a note appears on the laboratory analytical report stating the "observed sample pattern is not typical of #2 fuelldiesel, and the reported result is due to individual peak(s) eluting in the DRO range TPI-Id detections may represent weathered gasoline, but additional chemical analyses would have to be performed for verification Despite these fluctuations, there is an overall decreasing trend of contamination onsite This suggests that the plume is stable and declining . RECOMMENDATIONS Chevron and SECOR will contact the County representatives in early 2006 to discuss future activities for this site Until that time, SECOR recommends that site remain on a quarterly groundwater monitoring and sampling program through 2006 LIMITATIONS The conclusions and recommendations contained In this report/assessment are based upon professional opinions with regard to the subject matter These opinions have been arrived at in accordance with currently accepted hydrogeologic and engineering standards and practices applicable to this location and are subject to the following inherent limitations I The data and findings presented in this report are valid as of the dates when the investigations were performed The passage of time, manifestation of latent conditions or occurrence of future events may require further exploration at the site, analysis of the data, and reevaluation of the findings, observations, and conclusions expressed in the report 2 The data reported and the findings, observations, and conclusions expressed in the report are limited by the Scope of Work The Scope of Work was defined by the request of the client, the time and budgetary constraints Imposed by the client, and availability of access to the site 3 Because of the limitations stated above, the findings, observations, and conclusions • expressed by SECOR in this report are not, and should not be, considered an N 1Fdes\Projects\Chevron\Retadl#9-86321Periodic Mon itonng1200619QMR2006 doe