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Californiaoegional Water Quality C Q � <br /> Central Valle Region 'I� , <br /> � y : ter- <br /> � 2oe5 <br /> Linda S.Adams 'C .Z Arnold <br /> Secretaryfor Sacramento Main Officetv'ENT NtaLTSchwarzenegger <br /> Environmental 11020 Sun Center Drive 4200,Rancho Cordova,California 956 (FG'li✓3U1�' t 1- Governor <br /> Protection Phone(916)464-3291 •FAX(916)4644645 PG ��c?\r'C <br /> http://www.waterboards.ca.gov/centralva]Iey <br /> 19 December 2006 <br /> Mr. Thomas Kosel <br /> ConocoPhillips Company <br /> 76 Broadway <br /> Sacramento, CA 95818 <br /> REVIEW OF SECOND QUARTER 2006 AND THIRD QUARTER 2006 GROUNDWATER <br /> MONITORING REPORTS, FORMER TOSCO BULK TERMINAL #10013, 3505 NAVY DRIVE, <br /> STOCKTON, SAN JOAQUIN COUNTY <br /> Staff of the California Regional Water Quality Control Board, Central Valley Region (Central <br /> Valley Regional Water Board) has reviewed the 31 July 2006 Second Quarter 2006 <br /> Groundwater Monitoring Report (Second QMR) and the 31 October 2006 Third Quarter 2006 <br /> Groundwater Monitoring Report (Third QMR) submitted by Earth Tech, Inc. (Earth Tech) on <br /> behalf of ConocoPhillips Company (CP) for the former Tosco bulk fuel terminal site located at <br /> 3505 Navy Drive in Stockton, San Joaquin County (Site). The Second QMR and Third QMR <br /> describe groundwater monitoring and remediation activities for second quarter 2006 and third <br /> quarter 2006, respectively. <br /> Shallow groundwater flow during the second quarter and third quarter 2006 was to the south to <br /> southwest at an average gradient of 0.004 foot per foot. The maximum groundwater chemical <br /> concentrations during the two quarters were 320 micrograms per liter (ug/L) Total Petroleum <br /> Hydrocarbons (TPH) as gasoline; 300 ug/L TPH diesel; 0.57 ug/L benzene; 13 ug/L methyl <br /> tertiary butyl ether (MITBE); and 2,800 ug/L tertiary butyl alcohol (TBA). In both reports, CP <br /> compared the groundwater chemical data with Environmental Screening Levels (ESLs) <br /> established by the San Francisco Bay Regional Water Quality Control Board (SF Bay Regional <br /> Water Board) for groundwater that is not a current or potential source of drinking water. <br /> CP dismantled the groundwater extraction and treatment system including the HiperOxidation <br /> (HiPoxTM) unit in August 2006 with concurrence from the Central Valley Regional Water Board <br /> by letter dated 21 July 2006. CP plans to conduct a 6-month groundwater oxygen injection <br /> pilot test to further reduce dissolved phase chemical concentrations at the site. Design and <br /> construction plans for this effort will be prepared during the fourth quarter 2006. <br /> REGIONAL WATER BOARD REVIEW COMMENTS <br /> CP references ESLs to compare groundwater chemical concentrations in the second quarter <br /> 2006. The SF Bay Regional Water Board established ESLs for use in the San Francisco Bay <br /> Region. All groundwater within the Central Valley Region is considered a current or potential <br /> California Environmental Protection Agency <br /> li Recycled Paper <br />