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California P-gional Water Quality Cont-4 Board , <br /> 1 <br /> Central Valley Region ` <br /> Karl E. Longley,SCD, P.E., Chair ,_ <br /> Linda S.AdamsArnold <br /> Sccrercn-r�a� <br /> 11020 Sun Center Urice 4200.Rancho Cordova.California 9>(,7U-61 14 SehwarzeneKger <br /> l:mv-onmenral Phone(916)464-3291 •PAX(916)46I-464 Govern... <br /> http://�\wvv.waterboards.ca.govicentralvalle� � <br /> ,'reser,;��„ tlJUlf� C�w�04�I�D <br /> 8 August 2008 <br /> AUG t 1 2008 <br /> ENVRONk1ENT HEALTH <br /> Ms. Shelby Lathrop <br /> ConocoPhillips Company PERMIT/SERVICES <br /> 76 Broadway <br /> Sacramento, CA 95818 <br /> OXYGEN INJECTION PILOT STUDY REPORT, FORMER TOSCO BULK TERMINAL <br /> #10013, 3505 NAVY DRIVE, STOCKTON, SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Regional Water <br /> Board) staff reviewed the 25 July 2008 Oxygen Injection Pilot Study Report (Report) submitted <br /> by Stantec (formerly SECOR International Inc.) on behalf of the ConocoPhillips Company <br /> (ConocoPhillips) for the former Tosco bulk fuel terminal at 3505 Navy Drive in Stockton (Site). <br /> NuStar Energy currently owns and operates the Site. <br /> The Report documents the completion of the scheduled 180-day mobile oxygen injection pilot <br /> study. ConocoPhillips proposed to conduct groundwater monitoring for geochemical <br /> parameters and petroleum related constituents at 60 days, three months, and six months <br /> following the start of oxygen injection. The Report documents the results of 12 biweekly <br /> oxygen injection events performed at the Site between December 2007 and June 2008. <br /> The hydrostratigraphy underlying the Site is described as consisting of three progressively <br /> deeper layers called the A, B, and C zones. The A zone occurs at depths of about <br /> 10 to 25 feet below ground surface (bgs), the B zone from 30 to 50 feet bgs, and the C zone <br /> from 55 to 75 feet bgs. <br /> Twelve oxygen injection points (IP-1 through IP-12) were installed in June 2007. IP-1 through <br /> IP-9 are in the A zone, and IP-10 through IP-12 are in the B zone. The objective of the pilot <br /> study was to maintain dissolved oxygen (DO) levels at 10 milligrams per liter (mg/L) or greater <br /> to enhance the biodegradation of residual constituents of concern (COCs). During previous <br /> injections, about 150 cubic feet of oxygen were injected into each well. ConocoPhillips <br /> increased this rate to 300 cubic feet during injections performed in May and June. <br /> ConocoPhillips estimates that a total of 2,964 pounds of oxygen have been injected. <br /> During the pilot study, groundwater monitoring for COCs and geochemical parameters was <br /> conducted on 12 December 2007 and 20 February, 24 March and 26 June 2008 in eight <br /> monitoring wells (MW-2, MW-8, MW-10, MW-14, MW-16, MW-17B, MW-19C, and MW-20). <br /> Six of these wells monitor the A zone. MW-17B and MW-19C monitor the B and C zones, <br /> respectively. Pre- and post-injection groundwater monitoring for DO concentrations was <br /> conducted biweekly in seven of the eight monitoring wells listed above (except MW-10), and in <br /> piezometers P-1 through P-6. <br /> California Environmental Protection Agency <br />