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Mr. Eric Jenks 9 - 2 - is 16 February 2005 <br />upgradient investigation is completed this spring. GeoSyntec concludes that it is not practical to identify <br />each soil area that may have very low concentrations of bromacil or dinoseb. <br />Regional Board staff conceptually agree with the above reasoning. However, one of the peculiar <br />findings at this site is elevated nitrogen, bromacil and dinoseb in MW -3, which is situated upgradient of <br />the operations areas. To explore this anomoly, GeoSyntec proposes five of the soil borings in this <br />upgradient area. JTF should add analyses for carbamate/urea and chlorinated herbicide compounds to <br />the analytical suites proposed for samples from borings SSI -5, near MW -3, and SSI -6, near the wash <br />pad. These analyses will assist JTF and the Regional Board in ascertaining how much remediation, if <br />any, may be required upgradient of the operations area. <br />In the January 2005 Work Plan, GeoSyntec refers to soil excavation work that was done at the former <br />tank farm in 1991-1992 in conjunction with building the new tank farm. This excavation was also <br />mentioned in the 1 July 1999 Site Investigation Work Plan, but there is very little information on the <br />lateral extent of the excavation. If additional information can be obtained about this excavation, JTF <br />should mark this area on a site map, including the excavated dimensions and provide it with the soil <br />investigation Report of Results. <br />Summary <br />We concur with the Work Plan provided that JTF adds the following: <br />• Add a soil boring downgradient of Shop #3 and shift the position of SSI -16 to be downgradient of <br />Shop #2. <br />• Add analyses for chlorinated herbicides by EPA Method 8151 and carbamate/urea pesticides by EPA <br />Method 8321 to soil samples obtained from borings SSI -5 and SSI -6. <br />Thank you for preparing such a thorough work plan for source investigation and providing the <br />construction diagram for proposed MW -6. JTF may proceed with installation of MW -6 and may <br />coordinate the soil investigation with the upgradient and downgradient delineation. A combined Report <br />of Results is due by 14 May 2005. <br />If you have y questions, you may contact me at (916) 464-4680. <br />AM TERRELL <br />Private Sites Cleanup Unit <br />cc: Ms. Lori Duncan, San Joaquin County Public Health Services, Stockton <br />Mr. Thomas Slattery, Wilbur -Ellis Company, Fresno <br />Ms. Carolyn Kneiblher, GeoSyntec Consultants, Walnut Creek <br />