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Californil egional Water Quality Cor A Board <br /> Central Valley Region <br /> Karl E. Longley,ScD,P.E., Chair <br /> Linda S.Adams Arnold <br /> Secretary for 1685 E Street,Fresno,Cal(559)445 5910 Schwarzenegger <br /> Environmental (559)445-5116•Fax(559)445-5910 wGovernor <br /> Protection http://ww .waterboards.ca.gov/centralvalley <br /> (r D <br /> 21 November 2008 <br /> NOV 2 5 2008 . <br /> ENP6EAJN <br /> PERMIT/SERVICES <br /> M. Scott Mansholt <br /> Chevron Environmental Management Company <br /> 6111 Bollinger Canyon Road <br /> Rm 3432 <br /> San Ramon, California 94583 <br /> REVIEW— 2nd SEMI-ANNUAL 2008 GROUNDWATER SAMPLING AND MONITORING <br /> REPORT, VERNALIS PUMP STATION, 35500 WELTY ROAD, VERNALIS, SAN JOAQUIN <br /> COUNTY <br /> Chevron Environmental Management Company (Chevron) submitted the Second Semi-annual <br /> 2008 Groundwater Monitoring Report dated 26 September 2008, for the Vernalis Pump <br /> Station Site (Site). The report was prepared for Chevron by Science Applications International <br /> Corporation (SAIC). <br /> Monitoring wells (MW) -1 through 5 have been sampled on a quarterly to semi-annual basis <br /> commencing between 1998 and 2002. A minor amount of separate phase crude oil (SPO) <br /> has been observed in MW-1 since installation. An oleophilic sock is used in this well to <br /> remove SPO/water. MW-2 commonly has insufficient groundwater present and samples were <br /> not collected from May 2006 through January 2008. The semi-annual 2008 analytical results <br /> for total petroleum hydrocarbons as diesel (TPHd) were detected in MW-2 at concentrations of <br /> 52 and 110 micrograms per liter (pg/L), respectively. <br /> Central Valley Regional Water Quality Control Board (Central Valley Water Board) staff <br /> previously approved Chevron's recommendation to discontinue monitoring and destroy MW-3, <br /> 4, and 5 in 2007 and in May 2008. MW-2 has had insufficient water for sampling for some <br /> time and the well casing in MW-4 is damaged and samples cannot be obtained. <br /> According to SAIC's report: <br /> • Consistent with prior monitoring, depth to groundwater is approximately 36 feet below <br /> ground surface (bgs) with an easterly gradient. <br /> • MW-1 was not sampled due to the presence of SPO; approximately 0.02 gallons of <br /> crude oil/water has been removed since 1998. During the recent sampling event the <br /> oleophilic sock was inspected but not replaced. <br /> California Environmental Protection Agency <br /> 0� Recycled Paper <br />