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a -ai <br /> HarIen Knoll <br /> March 17, 1991 <br /> Page 2 <br /> Laboratory Analysis <br /> All samples were delivered within 24 hours to a California Certified analytical laboratory. <br /> Samples collected during this fourth round of sai-apling were analyzed for both purgeable <br /> halocarbons(EPA Method 601)and volatile aromatic hydrocarbons(EPA Method 602)per <br /> our discussion in February; 1991. Along with normal laboratory quality control measures, <br /> at least 10 percent spike and 10 percent duplicate samples will be run with each analysis <br /> set for quality assurance and quality control. A sample blank obtained by passing <br /> deionized water through a cleaned bailer was also analyzed to verify on-site <br /> decontamination procedures. <br /> Tht most significant analytical results are summarized below in Table 1,detailed analytical <br /> reports and field logs are provided in Appendix 1. <br /> Conclusions and Recommendations <br /> The absence o; volatile aromatic compounds and the presence o; only very law <br /> ( } concentrations of purgeable halogenated hydrocarbons indicates that there is little or no <br /> health risk associated with the uppermost groundwater, even if it were being used for <br /> public consumption. For example, 1,1,1 trichloroethane has been found consistently in the <br /> groundwater collected from MW-1 at Ievels ranging from 4.2 to.8 ug(L. The Primary <br /> Maximum Contaminant Level and EPAs goal for this constituent is 200 u 25 times the <br /> concentration actually.frund in the ginundwater. As a result, Murray & Associates <br /> recommends that <br /> Mr. Lambert Barnum be allowed to discontinue the groundwater <br /> monitoring program at the Stan Mori Ford Dealership in Tracy, and that a Site Closure <br /> be granted. <br /> r If you have any questions concerning this data, or would like additional information, please <br /> call me at your earliest convenience. <br /> ;ient <br /> rely, <br /> S. Murray, Ph.D. <br /> President <br /> KSM:cal <br /> '. s cc: Mr. Lambert C. Barnum <br />