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California -.egional Water Quality Co -ol Board °-, <br /> Central Valley Region <br /> .�. <br /> Karl E. Longley,RD, PE,Chair <br /> Linda S.Adams Arnold <br /> Secrelarn or Fresno Branch Office <br /> I Schwarzenegger <br /> Environmental 1685 E Street,Fresno,California 93706 <br /> Protection (559)445-5116•Fax(559)445-5910 Governor <br /> http://www.waterboards.ca.gov/centralvalley <br /> I EVED <br /> 8 May 2008 <br /> MAY 12 2008 <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, California 94583-2324 <br /> REVIEW — 2008 SEMI-ANNUAL GROUNDWATER SAMPLING AND MONITORING <br /> REPORT, US CAN-WELTY ROAD PROPERTY, VERNALIS, SAN JOAQUIN COUNTY <br /> Regional Water Board staff has reviewed the referenced document, dated 16 April 2008, <br /> describing field sampling activities for the US Can-Welty Road project monitoring wells. The <br /> report was submitted by Science Applications International Corporation (SAIC) on behalf of <br /> Chevron. <br /> According to SAIC's sampling and monitoring report: <br /> • Onsite monitoring wells MW-1 and 2 contain petroleum sheen and are not sampled; <br /> approximately 0.39 gallons of crude oil/water has been removed since 1999; new <br /> oleophilic (absorbent) socks were installed and annual inspection/replacement will <br /> continue; <br /> • Detectable total petroleum hydrocarbon as diesel (TPHd) of 1,600-pg/L was reported in <br /> MW-3; detectable concentrations of three PAHs (polynuclear aromatic hydrocarbons) <br /> exceeding Environmental Screening Levels (ESLs) were reported; monitoring events <br /> from May 2006 to August 2007, reported insufficient water present for sampling MW-3; <br /> however, during the recent event, sufficient water was present and MW-3 was sampled; <br /> • TPHd and PAHs were non detect (ND) for MW-4; MW-5, on adjacent Western Farms <br /> Services property is not accessible for sampling; and, <br /> • Depth to water, between 34 and 36 feet with an easterly gradient, is consistent with <br /> prior information. <br /> SAIC recommended that MW-4 and MW-5 should be properly destroyed in accordance with <br /> appropriate San Joaquin County well abandonment guidelines and MW-3 should be sampled <br /> an additional quarterly event provided sufficient water is available. <br /> California Environmental Protection Agency <br /> C4Recycled Paper <br />