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California Regional Water Quality Control Board <br /> Central Valley Region <br /> Robert Schneider,Chair <br /> Alan C.Lloyd,Ph.D. Arnold <br /> Secretoryfor Fresno Branch Office Schwarzenegger <br /> Environmental 1685 E Street,Fresno,California 93706 Governor <br /> Protection :// 445-5116•Fax a.gov cmu- 110 <br /> http://www.watedtoards.ca.gov/centmlvalley <br /> NOV 1 0 2005 <br /> 9 November 2005 <br /> ENVIRONMENT HEALTH <br /> PERMIT/SERVICES <br /> M. Scott Mansholt <br /> Chevron Environmental Management Company <br /> 6001 Bollinger Canyon Road <br /> Rm K2066 <br /> San Ramon, CA 94583-2324 <br /> REVIEW-2005 GROUNDWATER MONITORING AND SAMPLING-SECOND SEMI ANNUAL <br /> EVENT AND 2005 ANNUAL REPORT, FORMER LYOTH LOADING STATION, TRACY,SAN <br /> JOA QUIN COUNTY <br /> We have reviewed the referenced report, dated 24 October 2005, prepared for Chevron by Science <br /> Applications International Corporation (SAIC). <br /> On 26 August 2005, SAIC conducted the second semi-annual monitoring and sampling event for 2005 at <br /> the project site. Groundwater samples were obtained from three on-site wells and two off-site wells. A <br /> sixth well, MW-2 has not been sampled for several years due to the presence of floating sheen in the well. <br /> Subsequently, an oleophilic (hydrocarbon-absorbing) sock has been used for removing the sheen from this <br /> well. However, over the previous sampling events, it appears that minimal petroleum hydrocarbons <br /> remain in this well and the sock has not been changed for several events. <br /> This event, total petroleum hydrocarbons as diesel (TPHd)was reported at 420, 630, and 52 µg/L in <br /> monitoring wells MW-1, 6, and 7, respectively. TPHd was non detect (ND) for the other wells; in <br /> addition, TPH as gasoline(TPHg) and BTEX(benzene, toluene, ethylbenzene and xylene) compounds <br /> were ND in the five wells. Polynuclear aromatic hydrocarbons (PARS) were ND, except for MW-1 <br /> where concentrations of certain PAHs ranging from 0.02 to 0.03 µg/l,were reported. MW-2 was not <br /> sampled due to the presence of the absorbent sock. <br /> Depth to water measurements (12 to 15 feet) and gradient (NE) remain consistent with previous <br /> monitoring events. <br /> Based on the results and finding of the recent semi-annual sampling and monitoring event, SAIC <br /> recommended that since the amount of petroleum sheen noted in MW-2 is minimal, this well should be <br /> sampled beginning with the next semi-annual event in February 2006. <br /> California Environmental Protection Agency <br /> pia Recycled Paper <br />