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Mr. Jeff Baker 3 - 18 September 2008 <br /> Tesoro Companies, Inc. <br /> Our comments are presented below. <br /> 1. Regional Water Board staff does not believe that Tesoro's plan to terminate the boring at a <br /> maximum depth of 135 feet bgs will be effective to determine the total depth of the plume. <br /> On 15 September 2008, 1 spoke with Mr. Gary Haeck of Stantec and Mr. Jeff Baker of <br /> Tesoro by telephone. I stated that adequate vertical delineation required defining the plume <br /> to background and requested that the sampling plan be amended to drill, sample and <br /> analyze groundwater samples as deep as necessary to locate non-detectable (ND) levels <br /> of pollutants. Tesoro stated that cost-effective implementation of this requirement would <br /> require a phased approach. Tesoro subsequently sent the 15 September 2008 Addendum <br /> to Evaluation of Remedial Alternatives for D Zone Groundwater(Addendum). The <br /> Addendum states that the current plan to drill to a maximum depth of 135 feet, collect grab <br /> groundwater samples and install a well will be implemented as the first part of a two-phase <br /> plan. If ND is not encountered in the first phase, a second phase will be proposed using <br /> more appropriate drilling equipment to go deeper and to address cross-contamination <br /> concerns. Tesoro sent the Addendum by email to allow the drilling to proceed within the <br /> next couple of weeks. Regional Water Board staff concurs with this approach. If necessary, <br /> we will request a work plan for Phase 2 following review of the Phase 1 report. <br /> 2. The groundwater data listed in the table above shows that A, B, and C zone groundwater in <br /> the vicinity of TS/MW-2D was degraded by the 1999 spill. Tesoro currently treats the <br /> groundwater in the upper water bearing units using an ozone sparge (OS) system <br /> consisting of 10 A zone and eight B zone ozone sparge wells. Monitoring results for this <br /> area, however, show that downward migration of the plume continues to cause increases <br /> in benzene and TPHg concentrations in TS/MW-2D despite the OS system and the <br /> reported reduced post 1998 downward vertical gradients. Therefore, restricting additional <br /> remediation to the D zone, as proposed in the Evaluation, will not address the <br /> contamination in the C zone water bearing units. <br /> Regional Water Board staff concurs with the Evaluation as modified by the Addendum. By <br /> 15 December 2008, please submit a well installation report and a pilot study work plan that <br /> proposes remediation testing of the C zone as well as the D zone. If you have any questions <br /> regarding this letter, you may contact me at (916) 464-4811 or by email at <br /> betaylor@waterboards.ca.gov. <br /> 1, <br /> ii BRIAN TAYLOR, P.G. <br /> Engineering Geologist <br /> cc: Ms. Margaret Lagorio, San Joaquin County Environmental Health Department, Stockton <br /> Mr. Mark Chandler, Time Oil Company, Seattle, WA <br /> Mr. Sergio Morescalchi, BP, San Ramon <br /> Mr. Gary Haeck, Stantec Consulting Corporation, Rancho Cordova <br /> Mr. Jeffrey Wingfield, Port of Stockton <br /> Mr, Mark O'Brien, Environmental Risk Services Corporation, Alamo <br /> Mr. Jeremy Hughes, Levine Fricke, Granite Bay <br /> Mr. Joe Aldridge, NuStar, San Antonio, TX <br /> Ms. Amanda Spencer, Ash Creek Associates, Portland, OR <br />