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uamornia megionai water yuanty t_;ontro oar <br /> ` Central Valley Region <br /> Karl E. Longley,SCD,P.E.,Chair 0 0 <br /> Linda S.Adams 11D20 Sun Center Drive#200,Rancho Cordova,California 9567MI14 Arnold <br /> nvSecronmenor Phone(916)464-3291 •FAX(916)464-4645 Schwarzenegger <br /> Enrotect enlal <br /> Protection http://www.waterboards.cntralvalley Governor <br /> 9..gpv <br /> 13 March 2009 ECIEVED <br /> MAR 1 7 2009 <br /> Mr. Joe Lentini ENVIRONMEN''THEALTH <br /> Shell Oil Products US PERMIT/SERVICES <br /> 20945 S. Wilmington Avenue <br /> Carson, CA 90810 <br /> REVIEW OF SITE INVESTIGATION REPORT, FORMER SHELL CRUDE OIL PIPELINES, <br /> HANSEN ROAD NEAR SCHULTE ROAD, TRACY, SAN JOAQUIN COUNTY <br /> Staff of the California Regional Water Quality Control Board, Central Valley Region (Regional <br /> Water Board) has reviewed the 8 January 2009 Site Investigation Report, Former Shell Crude <br /> Oil Pipelines, Cordes Ranch, Hansen Road near Schulte Road, Tracy (Report) submitted by <br /> Conestoga-Rovers &Associates (CRA) on behalf of Equilon Enterprises LLC doing business <br /> as Shell Oil Products US (Shell). The Report details the results of further investigation of <br /> petroleum hydrocarbons dissolved in groundwater through vertical profiling. <br /> Two borings were advanced using a cone penetrometer testing (CPT) rig approximately 160 <br /> and 240 feet northeast (inferred down gradient direction) of the former pipeline in the area of <br /> Trench 3 where deeper groundwater samples had been previously collected. Groundwater <br /> samples were collected using a Hydropunch sampling tool at 9 to 28-foot depth intervals <br /> between 40 and 146 feet below ground surface (bgs). The samples collected from B-77 <br /> contained concentrations of Total Petroleum Hydrocarbons (TPH) as crude oil (TPHcr) ranging <br /> from less than the detection limit of 250 micrograms per liter (Ng/L) at depths of 44 to 84 feet <br /> and 146 feet bgs to a maximum concentration of 2,500 pg/L at a depth of 122 feet bgs. <br /> Similarly TPH as diesel (TPHd) ranged in concentration from less than the detection limit of 50 <br /> Ng/L at 66 feet bgs to 1,100 pg/L at 122 feet bgs. B-78 is located approximately 80 feet down <br /> gradient of B-77, and only the 120- and 146-foot samples contained detectable levels of <br /> TPHcr and TPHd at maximum concentrations of 570 and 310 Ng/L, respectively. Based on <br /> the pattern of decreasing concentrations in the down gradient direction, CRA estimates that <br /> the TPH concentrations attenuate to below detectable levels within an additional 80 to 100 feet <br /> down gradient of B-78. <br /> CRA also conducted a field survey to identify any additional water supply wells not previously <br /> identified as part of a California Department of Water Resources records search. This search <br /> identified one additional water supply well located approximately 2,200 feet up gradient from <br /> the former pipeline alignment. CRA attempted to contact the owners of the three previously <br /> identified wells that are in closer proximity to the former pipeline alignment, but the owners <br /> could not be located. <br /> California Environmental Protection Agency <br /> ct1 Recycled Paper <br />