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i <br /> Mr. John MacLeod - 2 - 13 March 2006 <br /> i <br /> Remediation at the site currently consists of monitored natural attenuation. Chevron semiannually <br /> samples five monitoring wells adjacent to the location of the release. Three of these wells, MW-6, <br /> MW-8 and MW-12'continue to contain TPHd, TPHg, BTEX and PNAs. Most recent monitoring shows <br /> that MW-6 contains the most contamination, including 30,000 ug/1 TPHd, 2,700 ug/l of TPHd, 36 ug/l of <br /> benzene, and 210 ug/1 of naphthalene. MW-8 contains 690 ug/1 TPHd, 190 ug/1 TPHg, 1.6 ug/l benzene, <br /> and 48 ug/1 of naphthalene. MW-12 contains 690 ug/1 of TPHd, 350 ug/1 of TPHg, 110 ug/1 of benzene <br /> and trace amounts of PNAs. <br /> Chevron requested revision of the MRP in their letter of 31 January 2006. Chevron recommended: <br /> • Continue monitoring of MW-6 and MW-12 because of the elevated benzene levels <br /> • Discontinue monitoring of MW-5, MW-7 and MW-8, and <br /> • Discontinue-monitoring-of bioremediation`parameters. -- -- <br /> Regional Water Board staff concur with the above request with the exception of MW-8, which must be <br /> monitored because it contains TPHd, TPHg, and naphthalene above water quality objectives. <br /> Enclosed is a draft revised MRP for Chevron's review and comment. Please provide comments on the <br /> revised MRP by 2 May 2006. If you have any questions, you may contact me at (916) 464-4677 or by <br /> email,at gdjuth(2cwaterboards.ca.gov. <br /> 1,4 <br /> GERALD J. DJUTH, P.E.; C.E.G. <br /> Associate Engineering Geologist <br /> cc: Ms. Margaret Lagorio, San Joaquin County Public Health Services, Stockton <br /> Mr. Allen Just, BBL,Irvine <br /> Attachment <br /> `7 -- r - - - - -- - <br /> I <br /> N <br /> ;i f <br />