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California r'-%gional Water Quality Cor` �ol Board <br /> \� Central Valley Region t } <br /> Kathrine Hart, Chair <br /> Linda S.Adams 11020 Sun Center Drive ?200,Rancho Cordova,.California 95670-6114 Edmund G. Brown Jr. <br /> Acting Secretary/or Governor <br /> Environmental (9 16)464-3291 •FAX(916)464-4645 <br /> Protection �- - htt a/www.waterboards.ca.gov/cenlralvalley <br /> 8 March 2011 JUN 24 2� i <br /> Ms. Shelby LairraI.TWRONMENTAL HEALTH <br /> RMIT/SERVICES <br /> ConocoPhillips Company <br /> 76 Broadway <br /> Sacramento, CA 95818 <br /> FOURTH QUARTER AND ANNUAL 2090 STATUS SUMMARY REPORT, FORMER TOSCO <br /> - BULK TERMINAL-410013, 3505 NAVY DRIVE;--STOCKTON, SAN-JOAQUIN COUNTY - <br /> California Regional Water Quality Control Board, Central Valley Region(Central Valley Water <br /> Board).staff reviewed the 28 January 2011 Fourth Quarter and Annual 2090 Status Summary <br /> Report (Annual Report) and-the 14 February 2011 Addendum Work Plan for Human Health <br /> Risk Assessment (Addendum) submitted on behalf of the ConocoPhillips Company <br /> (ConocoPhillips) by Stantec Consulting Corporation (Stantec)for the former Tosco bulk fuel <br /> terminal at 3505 Navy Drive in Stockton (Site). ConocoPhillips conducts groundwater <br /> monitoring at the Site pursuant to Monitoring and Reporting Program No. R5-2004-0824, <br /> NuStar Energy (NuStar) currently owns and operates the Site. <br /> Groundwater underlying and downgradient of the Site has been degraded with low levels of <br /> contaminants of concern (CDCs), including total petroleum hydrocarbons as diesel (TPHd), <br /> tertiary butyl alcohol (TBA), methyl tertiary butyl ether (MTBE), TPH as gasoline (TPHg), and di- <br /> isopropyl ether (DIPE). Since December 2007, remediation has consisted of injecting <br /> pressurized oxygen into up to 16 injection wells installed in contamination hot-spots. <br /> Monitoring for the fourth quarter was conducted on 3 December 2010. Table 4 shows that <br /> TPHd concentrations ranged from 130 to 410 micrograms per liter (pg/L). Fourth quarter <br /> monitoring was not conducted in MW-18C, which had a third quarter spurious TPHd <br /> concentration of 1,900 pg/L. TBA was detected in only one well at 35 pg/L. The highest <br /> concentration of MTBE was 2.3 pg/L. TPHg was not detected above laboratory reporting limits. <br /> The elevated concentrations of methanol observed in six wells during the first quarter of 2010, <br /> ranging from 1,200 pg/L in MW-19C to 60,000 pg/L in MW-17B, were absent during the next <br /> two consecutive quarters and were most likely anomalous. Methanol was not analyzed in any <br /> monitoring well samples during the fourth quarter. <br /> In most wells, contaminant concentrations are within the range of historical variations that <br /> immediately preceded and followed implementation of the mobile oxygen injection pilot study. <br /> TBA concentrations have decreased most distinctly in response to oxygen in MW-17B and <br /> MW21 B. <br /> After failing to sustain increases in dissolved oxygen (DO) concentrations or to achieve <br /> substantial reductions in COC concentrations after about six months of implementing the pilot <br /> study, in May 2008, ConocoPhillips increased the volume of the oxygen injections from <br /> California Environmental Protection Agency <br /> ZdRecycled Paper <br />