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J <br /> Touchstone performed additional site assessment to further define the extent of hydrocarbons in soil and <br /> groundwater A total of eight soil bonngs were dnlled and soil samples were collected dunng February, <br /> 1996 Groundwater samples were also collected from four of the bonngs Four of the eight soil bonngs <br /> were converted to groundwater monitonng wells <br /> The analytical results from soil samples detected the presence of gasoline, gasoline constituents, and <br /> MTBE There were also unidentified detections of hydrocarbons within the diesel range of analysis The <br /> results indicated that the extent of hydrocarbons in soil has been defined and that their occurrence is <br /> primarily linuted to the soils in the areas of the former UST complex and pump islands The results from <br /> Touchstone's"grab" groundwater samples at bonngs B-1 through B-4 indicated the presence of dissolved <br /> gasoline(and constituents)at all locations except,B-3 There were also detections of unidentified <br /> hydrocarbons within the diesel range at the same locations There were two samples (B-2 and B-4)which <br /> indicated the presence of MTBE The presence of MTBE suggests that the contaminant source is a <br /> Chevron product manufactured after 1992 The analytical summary provided by CRTC of free product <br /> recovered from the former UST excavation indicated that the product was highly evaporated which <br /> suggests that it was also probably"old" No confirmation has been received from CRTC yet as to whether <br /> or not the product analyzed contained MTBE In addition to obtaining this confirmation, Chevron <br /> recommends that MTBE be analyzed for in subsequent monitoring well samplings and that any detection <br /> of MTBE be confirmed by GUMS analysis (i c,EPA 8260) The scope of Touchstone's work did not <br /> include the development, sampling, or surveying of momtonng wells MW-I through MW-4 This work <br /> and subsequent results are to be performed and reported separately by another Chevron consultant <br /> Based on the results of Touchstone's findings it would seem appropnate to further define the extent of <br /> hydrocarbons in groundwater The scope of this additional investigation will be based on the findings of <br /> the planned groundwater momtonng event <br />�) If you have any questions or comments, please contact me directly at(510) 842-8695 <br /> Sincerely, <br /> XT"V-W/ /Zaz- <br /> Brett L Hunter <br /> Environmental Engineer <br /> Site Assessment and Remediation <br /> Attachments <br /> cc Leititia Briggs, San Joaquin County Public Health Services, P O Box 388, Stockton, CA <br /> 95201-0388 <br /> City of Tracy Fire Department,Prevention Division, 325 E 10th St, Tracy, CA 95376 <br /> Elizabeth Thayer, Central Valley RWQCB, Sacramento, CA <br /> Russell D Keil Jr,Keil Sonoma Corp , 244 Kearny St, San Francisco, CA 94108 <br />