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Stantec Consulting Corporation <br /> 3017 Kilgore Road Suite 100 <br /> Rancho Cordova CA 95670 <br /> Tel: (916)861-0400 <br /> Fax: (916)861-0430 <br /> Stantec <br /> April 30, 2010 <br /> Mr. Brian Taylor, P.G. 0 <br /> California Regional Water Quality Board ENVIRONMENT HEAT i H <br /> 11020 Sun Center Drive, Suite 200 PERMIT/SERVICES <br /> Rancho Cordova, California, 95670-6114 <br /> RE: Response to RWQCB Letter Dated March 11, 2010 <br /> Stockton Terminals Technical Committee <br /> Port of Stockton <br /> Stockton, California <br /> Dear Mr. Taylor, <br /> On behalf of the Stockton Terminals Technical Committee (STTC), Stantec Consulting <br /> Corporation (Stantec), would like to address comments in the Regional Water Quality Control <br /> Board's (RWQCB) March 11, 2010 letter addressed to Mr. Jeff Baker of Tesoro Companies, Inc. <br /> (Attachment 1) regarding the above referenced site. In your March 11, 2010 letter, the <br /> RWQCB's comments are in reference to both STTC and Atlantic Richfield Company (ARC), a <br /> BP Affiliated Company's Terminal No. 40T. <br /> Below please find the RWCQB comments in bold, with Stantec's response following. <br /> General Discussion, Page 2. During the fourth quarter, MBAS in 14 wells exceeded <br /> 500 µg/L. However, BP purged only 10 wells...MBAS concentrations in AR/MWAC, <br /> AR/MW-18C, and AR/MW-22A ranged from 630 µg/L to 930 gg/L. However, these wells <br /> were not over-purged. <br /> The above statement is inaccurate, ARC (a.k.a. BP) was in compliance with the interim remedial <br /> plan. See the response to RWQCB comment 4 below. <br /> 1. The presence of MBAS in AR/MW-18C at 930 µg/L about 800 feet downgradient, <br /> and at a depth of 60 to 70 feet bgs, indicates that the lateral and vertical extent of this <br /> contaminant is undefined. The prevailing downward vertical gradients documented in <br /> the Annual Report and the high hydraulic conductivity value documented in Table 1 of <br /> the 9 July 1996 Bioassessment and Bioenhancement Investigation, Stockton Terminals <br /> Technical Committee Distribution Terminals show that the MBAS detected in <br /> AR/MW-18C could have migrated from November 2008 loading rack spill. In addition, <br /> this detection indicated that the OS may be incapable of preventing the offsite <br /> migration of this contaminant. To evaluate the lateral and vertical extent of MBAS, BP <br /> must now conduct quarterly MBAS monitoring in downgradient wells OW-9C, <br /> PS/MW-20C, OW-3CR, and OW-4C and report the results in future quarterly reports. If <br /> the first quarter 2010 monitoring has yet taken place, these results should be reported <br /> in the first quarter report, which is due on 1 May 2010. <br /> Response to RWQCB letter dated 11 march 2010.FINAL.doc <br /> 1 <br />