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California Regional Water Quality Control Board <br /> Central Valley Region <br /> Karl E. Longley,ScD, Y.E.,Chair <br /> S. <br /> Linda S.Adams Arnold <br /> Secretary for 1685E Street,Fresno,California55 )44 93746 5ehwarzenegger <br /> Envrronmentaf (559)445-5116 1 Fax(5 59)445-5519 Governor <br /> hapJlwwwwaterhoards.ca.govfcentralvalley <br /> 21 November 2008 <br /> M. Scott Mansholt <br /> Chevron Environmental Management Company <br /> 6111 Bollinger Canyon Road <br /> Rm 3432 <br /> San Ramon, California 94583 <br /> REVIEW— 2"d SEMI-ANNUAL 2008 GROUNDWATER SAMPLING AND MONITORING <br /> REPORT, VERNALIS PUMP STATION, 35504 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 MVI!-2 at concentrations of <br /> 52 and 110 micrograms per liter (pglL), 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 /> • MVV-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 /> (t; Recycled Proper <br />