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Statttec <br /> Response to RWQCB Letter Dated March 11, 2010 <br /> Stockton Terminals Technical Committee <br /> April 30, 2010 <br /> 4. BP failed to over-purge two on-site wells, AR/MW-1C and AR/MW-22A, that <br /> contained MBAS in concentrations exceeding 500 µg/L. To comply with the interim <br /> remediation plan, BP must conduct over-purging in all on-site wells with MBAS <br /> exceeding 500 pg/L. <br /> BP was in compliance with the interim remedial plan. All accessible monitoring wells with <br /> MBAS reported above 500 µg/L during the previous sampling events (third quarter 2009 or <br /> before) were overpurged as required. MBAS was reported above 500 µg/L in AR/MW-1C and <br /> AR/MW-22A during the fourth quarter and, therefore, overpurging will begin in those wells <br /> starting with the first quarter 2010. <br /> 5. At its current rate of increase, the TBA concentrations in AR/MW-18B could <br /> potentially reach the compliance limit of 66 µg/L sometime between late 2010 and early <br /> 2011. Since three consecutive exceedences of this concentration would trigger <br /> installation of a second ozone sparge array east of the RO wells, BP should begin <br /> mapping this contaminant plume to more closely scrutinize its rate of migration and to <br /> formulate a plan to address this potential problem. <br /> TBA concentrations are mapped in the quarterly reports for the site. The reported TBA <br /> concentration in the sample from well AR/MW-18B decreased from 49 µg/L during the fourth <br /> quarter 2009 to 44 pg/L during the first quarter 2010. TBA trends will continue to be monitored. <br /> Should you have any questions or concerns regarding this letter, please feel free to contact me <br /> at 916.861.0400. Thank you for your continued assistance with the remedial progress of this <br /> site. <br /> Sincerely, <br /> Stantec Consulting Corporation OQ?,oFESS/p�A <br /> BEh-.0 <br /> � <br /> C5 99 <br /> 4jj <br /> sky' <br /> P * EXP.12/31/2010 <br /> Managing Principal gineer sl CIVIL P <br /> q"FOFCAL\F <br /> cc: Mr. Paul Supple, BP <br /> Mr. Jeff Baker, Tesoro <br /> Mr. Mark Chandler, TOC Holdings Company <br /> Ms. Margaret Lagorio, San Joaquin County Environmental Health Department <br /> Mr. Jeffrey Wingfield, Port of Stockton <br /> Mr. Mark O'Brien, Environmental Risk Services Corporation <br /> Mr. Jeremy Hughes, Arcadis <br /> Mr. Joe Aldridge, NuStar <br /> Ms. Amanda Spencer, Ash Creek Associates <br /> Attachment RWQCB Letter Dated March 11, 2010 <br /> Response to RWQCB letter dated 11 march 2010.FINAL.doc 3 <br />