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Californi Iegional Water Quality Co rol Board <br /> r-N QW; Central Valley Region <br /> Karl E. Longley,ScD, PE,Chair <br /> Linda S.Adams Arnold <br /> Secretaryjor Fresno Branch Office Schwarzenegger <br /> Environmental 1685 E Street,Fresno,California 93706 <br /> 559 445-5116•Fax 559 445-5910 Governor <br /> Protection � � � � <br /> http://www.waterboards.ca.gov/centra]valley <br /> LE V E <br /> 8 May 2008 MAY 12 2008 <br /> EMAR10NI[l ENT HEALTH <br /> PEfilkilTUSERVICES <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, VERNALIS PUMP STATION, 35500 WELTY ROAD, VERNALIS, SAN JOAQUIN <br /> COUNTY <br /> Regional Water Board staff has reviewed the referenced document, dated 28 April 2008, <br /> describing field sampling activities for the Vernalis Pump Station 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 well MW-1 contains a petroleum sheen and is not sampled; <br /> approximately 0.02 gallons of crude oil/water has been removed since 1998; SAIC <br /> requested that inspection and replacement of the oleophilic (absorbent) sock be <br /> reduced to semi-annual to coincide with groundwater monitoring; <br /> • Detectable total petroleum hydrocarbon as diesel (TPHd) at 52, 79, 73, ND, and <br /> 390-pg/L, respectively was reported in MWs-2, 3, 5, 6, and 7; MW-4 has not contained <br /> sufficient water for sampling since early 2006 and it was noted the surface well casing <br /> has been damaged; SAIC recommended that this well be properly destroyed; <br /> • PAHs were ND and have been ND since early 2007; SAIC recommended that since <br /> only low PAH concentrations or ND results have been reported in the monitoring wells <br /> for approximately two to six years, sampling and analysis of PAH compounds be <br /> discontinued; and, <br /> • Depth to water, between 33 and 37 feet with an easterly gradient, is consistent with <br /> prior information. <br /> California Environmental Protection Agency <br /> Za Recycled Paper <br />