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Californiafpgional Water Quality C4Frol Board <br /> CGI V G0 Central Valley Region <br /> G Katherine Hart, Chair <br /> Linda S.Adams 1"N20 Governor <br /> 20 Sun Center Drive#200, Rancho Cordova,California 95670-6114 Edmund G.Brown Jr. <br /> Acting Secretary/or f. K 1 1 ,! (916)464-3291 •FAX(916)464-4645 <br /> Environmental �c,il http://www.waterboards.ca.gov/centralvalley <br /> Protection -t{ <br /> Etavta"�" 16 March 2011 <br /> Mr. Kevin E. Dyer <br /> Shell Oil Products US <br /> 17 Junction Drive, PMB #399 <br /> Glen Carbon, IL 62034 <br /> GROUNDWATER MONITORING REPORT, FORMER SHELL CENTRAL VALLEY <br /> CRUDE OIL PIPELINES, CORDES RANCH, HANSEN ROAD NEAR SCHULTE <br /> ROAD TRACY, SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley <br /> Water Board) staff reviewed the 28 February 2011 Groundwater Monitoring Report— <br /> Fourth Quarter 2010 (Fourth QMR) for the Former Shell Central Valley Crude Oil <br /> Pipeline at Hansen Road near Schulte Road in Tracy (Site) on behalf of Equilon <br /> Enterprises LLC doing business as Shell Oil Products US (Shell). Shell voluntarily <br /> sampled the wells in August after they were installed between 12 July and <br /> 23 August 2010. <br /> The Fourth QMR summarizes the results of sampling in December of 13 wells (MW-1 <br /> through MW-4, MW-5A, MW-5B, MW-5C, and MW-6 through MW-11) installed along <br /> the central portion of the former pipeline alignment. All wells except MW-5B and <br /> MW-5C are shallow wells and installed at a maximum depth of 50 feet below ground <br /> surface (bgs). MW-513 and MW-5C are deeper wells with total depths of 115 and <br /> 180 feet bgs, respectively. Depth to groundwater varied from about 32 to about 37 feet <br /> bgs in the shallow zone, 33 feet bgs in the intermediate zone, and 56 feet bgs in the <br /> deep zone. Using the groundwater levels measured in the shallow wells, Shell <br /> calculated that the groundwater flow is to the northwest at a gradient of about <br /> 0.001 feet per foot. <br /> Laboratory analytical results show that total petroleum hydrocarbons as crude (TPHc), <br /> TPH as diesel (TPHd), benzene, and ethylbenzene are present in groundwater samples <br /> collected from MW-2 and MW-5A. Detections at these locations coincide with soil <br /> detections observed in August 2010. The groundwater sample collected from MW-2 <br /> contained the maximum TPHc and TPHd concentrations at 11,000 micrograms per liter <br /> (pg/L) and 6,800 fag/L, respectively. Benzene concentrations were 190 pg/L in MW-2 <br /> and 400 pg/L in MW-5A. Ethylbenzene was present at low concentrations. TPHc and <br /> TPHd concentrations decreased since August, and benzene concentrations increased. <br /> In response to our 5 November 2010 letter which requested that Shell conduct <br /> hydropunch sampling prior to installing proposed wells, Shell's 17 January 2011 Site <br /> Assessment Work Plan (Work Plan) proposed to <br /> advance a total of 19 exploratory soil borings along the pipeline right-of-way, <br /> including 10 northwest of MW-1 in Area 1 and nine southeast of Area 6; <br /> California Environmental Protection Agency <br /> CjsRecycled Paper <br />