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h <br /> ^ Wright <br /> _ Environmental <br /> Services, Inc. <br /> March 7. 2000 Construction ♦ Engineering • Remediation <br /> Project No. 4070 <br /> M & M Automotive <br /> 60 East 10th Street <br /> Tracy. CA 95376 <br /> Atm: Mr. Richard McLean and Larry McLean <br /> Re: Workplan for Additional Site Investigation <br /> 60 E. 10th Street - Site Code 2554 <br /> Gentlemen. <br /> WriGht Environmental Services. llnc. (Wright) is pleased to provide you with this workplan <br /> for the eprvironmental investigation at the above referenced site (,see Figure 1). The purpose <br /> of this work is to ascertain suspected petroleum contaminants in soil and Groundwater and <br /> install a replacement monitoring well in and around the former tank area as required by the <br /> San Joaquin County Public Health Services Environmental Health Division (PHS EHD in <br /> 999 and discussion with the PHS EHD representative. <br /> their letter dated December 20. 1 <br /> Background and Technical Approach <br /> Wright has performed several phases of work at this site.. the latest of which was a source <br /> excavation and monitoring well abandonment as a result of the excavation. The results of <br /> the excavation removed contaminated soil at the capillary fringe and upper portion of the <br /> shallow aquifer in the former underground storage tank area. The soil sampling revealed <br /> contaminants remained in the capillary fringe region and an estimate of remaining <br /> contaminant mass indicated that a very low calculated quantity of Total Petroleum <br /> Hvdrocarbon as Gasoiine and Benzene were present. Former well MW-1 had historically <br /> displayed dissolved contaminants at varying, but at similar concentration ranges. The <br /> dissolved plume has historically been compact and centered around this well. Wright may <br /> reinstall the well pending the results of the vertical extent sampling discussed herein. <br /> Wright's approach to this work is to ascertain whether contaminants occur at the <br /> aquifer/aquitard contact at former MW-1 and within the excavation perimeter (see Figure <br /> 1). Borinas will be advanced to the aquifer/aquitard contact to collect discrete groundwater <br /> samples in the source area depth (lower aquifer contact at depth -16-17 feet) with a discrete <br /> sroundwater sampler, including one located at former MW-1. Each boring will be <br /> advanced into the aquitard to collect discrete soil/sediment samples at least two feet (at <br /> depth 19 feet) into the aquitard. Additional samples will be collected at five foot intervals to <br /> ascertain potential aquitard contaminant penetration. At least two aquitard vertical definition <br /> samples will be collected for analysis from each borehole. more samples may be collected <br /> based upon field evidence of contaminant presence in the boreholes. <br /> Boreholes may be advanced deeper to ascertain contaminant penetration if any is observed <br /> however, any boring will be terminated if field judgment indicates deeper drilling could <br /> potentially enhance vertical contaminant movement. A conductor cased sealed borehole <br /> through the upper aquifer and/or contaminant source will be used to advance to deeper <br /> aquifers/aquitards if necessa5 <br /> 67 E. 10th Street • Tracy, CA 95376 <br /> 209.833.0758 . Fax 209.832.5152 <br /> wright@inreach.com Lic. #651501 R-B HazMat <br /> websit http://home.inreach,com/wright Page 1 <br />