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OEOMATRIX <br /> Mr. M. Scott Mansholt <br /> Chevron Environmental Management Company <br /> July 8, 2003 <br /> Page 2 <br /> anticipate that a rhino rig likely will be able to advance to about 50 feet bgs at this site. The <br /> proposed revised soil and groundwater sampling plan is described below: <br /> 1. Continuous soil samples will be collected from each boring for lithologic logging and <br /> field screening. Field screening includes measuring the concentrations of total volatile <br /> organic compounds in the headspace of a soil sample using a photoionization detector <br /> and examining a soil sample for discoloration and/or petroleum odor. <br /> 2. A grab groundwater sample will be collected using a HydroPunch sampler from about <br /> 36 to 40 feet bgs in each boring for laboratory analyses. <br /> 3. A soil sample will be collected for laboratory analyses from the interval of petroleum- <br /> affected soil within the vadose zone in each boring, if observed. If petroleum-affected <br /> soil is not observed within the vadose zone of a boring, then a soil sample will be <br /> collected for laboratory analyses from a depth above the water table. Another soil <br /> sample will be collected for laboratory analyses from the terminus of each boring. <br /> The analytical methods for the grab groundwater and soil samples are described in the Work <br /> Plan. After discussions, Mr. Hubbard of the RWQCB approved the revised drilling approach <br /> in a July 2, 2003, telephone conversation. Geomatrix will apply for a drilling permit from the <br /> San Joaquin County on behalf of ChevronTexaco. The field sampling activities have been <br /> tentatively scheduled for the week of August 4, 2003. <br /> Sincerely yours, <br /> GEOMATRIX CONSULTANTS, INC. <br /> Veen Chee Foong, P.E. <br /> Senior Engineer <br /> 1:\PROJECIN6000s\6447.000\001 Welty\US Can Soil-Gw WP Amendment.doc <br />