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F � <br /> California Rcional Water Quality An'rrol Board <br /> Central Valley Region <br /> Robert Schneider,Chair <br /> Linda S.Adams Arnold <br /> Secremryfor Fresno Branch Office Schwarzenegger <br /> Environmental 1685 E Street,Fresno,California 93706 Governor <br /> Protection (559)445-5116•Fax(559)445-5910 <br /> http://www.waterboards.ca.gov/centralvalley <br /> FRECOVED <br /> 16 November 2006 NOV 1 7 2006 <br /> EWIp.nl,wENT HEALTH <br /> pE~,:v;i i/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- GROUNDWATER MONITORING AND SAMPLING - SECOND SEMI ANNUAL <br /> EVENT AND 2006 ANNUAL REPORT, FORMER LYOTH LOADING STATION, TRACY, <br /> SAN JOAQUIN COUNTY <br /> Regional Water Board staff has reviewed the referenced report, dated 24 October 2006, <br /> prepared for Chevron by Science Applications International Corporation (SAIC). On 8 August <br /> 2006, SAIC conducted the second semi-annual 2006 monitoring and sampling event for the <br /> project site. Quarterly groundwater monitoring has been conducted at the site since 1997 and <br /> on a semi-annual basis since 2002. <br /> Groundwater samples were obtained from three on-site wells and two off-site downgradient <br /> monitoring wells. A sixth well, MW-2 has not been sampled for several years due to the <br /> presence of floating petroleum sheen. Minimal petroleum hydrocarbons remain in this well <br /> and the oil-absorbing (oleophilic) sock has not been changed for some time. <br /> This event, total petroleum hydrocarbon as diesel (TPHd) was reported at 58, 230, and 480 <br /> Ng/L in monitoring wells MW-1, 4, and 6, respectively, and non detect (ND) for the other wells. <br /> Total petroleum hydrocarbon as gasoline (TPHg) and BTEX (benzene, toluene, ethylbenzene <br /> and xylene) compounds were ND in all samples. Polynuclear aromatic hydrocarbons (PAHs) <br /> were ND, except for low concentrations of phenanthrene (0.01 to 0.04 pg/L) reported in two <br /> wells. The PAH values are below regulatory environmental screening levels and/or water <br /> quality objectives. Depth to water measurements (13 to 19 feet and north-northwest gradient) <br /> remain consistent with previous monitoring events. <br /> Based on the historical and current findings, SAIC recommended that since TPHg and BTEX <br /> have not been reported at the site since 1997, these petroleum constituents be removed from <br /> the sampling program. Additionally, groundwater conditions have remained relatively <br /> California Environmental Protection Agency <br /> �i p�Recycled Paper <br />