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- Californi- Ilegional Water Quality Co- '-ol Board <br /> Central Valley Region <br /> Karl E. Longley,ScD, PE,Chair .60 <br /> Linda S. Adams Arnold <br /> Secretaiyfor Fresno Branch Office Schwarzenegger <br /> Environmental 1685 E Street,Fresno,California 93706 Governor <br /> Protection (559)445-5116•Fax(559)445-5910 <br /> http://",%v.waterboards.ca.gov/centralvalley R E(�9 F© <br /> 16 August 2007 AUG 2 0 2007 <br /> ENVIROMi IEfvT HEALTH <br /> PEMV1!T/SE9, V!CES <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 OF SECOND QUARTER 2007 GROUNDWATER MONITORING AND SAMPLING <br /> REPORT — FORMER VERNALIS PUMP STATION PROPERTY, VERNALIS, SAN JOAQUIN <br /> AND STANISLAUS COUNTIES <br /> Regional Water Board staff has reviewed the referenced groundwater sampling report, dated <br /> 24 July 2007, prepared for Chevron by Science Applications International Corporation (SAIC). <br /> The Vernalis site consists of two properties: Bellini, the northern triangular portion (formerly <br /> Roberts) and the southern Arcos property. The properties were part of the former Vernalis <br /> Pump Station previously owned and operated by predecessors of Chevron as part of the <br /> historical Old Valley Pipeline (OVP) system. <br /> Generally, petroleum affected groundwater has been adequately delineated on the Arcos and <br /> Bellini properties but not offsite and downgradient on the adjacent Bogetti property, east of <br /> Highway 33 and the railroad tracks. In a 14 February 2007 letter to Chevron, Regional Water <br /> Board staff concurred with a request that future Bogetti property investigations be addressed <br /> separately. In a 4 May 2007 letter, Regional Water Board staff approved a workplan for <br /> additional downgradient borings and groundwater assessment on the Bogetti property. <br /> Monitoring wells (MW) MW-6 and MW-7 are located on the Bogetti property. These two offsite <br /> wells and five onsite wells have been monitored irregularly since 1998 and quarterly since <br /> early 2005. This event monitoring and sampling were completed on 8 May 2007. <br /> The groundwater elevation has steadily declined and three onsite wells (MW-2, 3, and 4) have <br /> not had sufficient water for sampling since January 2006. Onsite well, MW-1 has contained a <br /> sheen since it was constructed in 1998 and is not sampled (a petroleum-absorbing sock <br /> device is used in this well and changed as needed). Groundwater flow is east with an <br /> approximate gradient of 0.001 ft/ft. Depth to water is between 34 and 38 feet. <br /> Groundwater samples obtained from onsite well, MW-5 and offsite wells MW-6 and 7 were <br /> submitted for total petroleum hydrocarbons as diesel (TPHd) and polynuclear aromatic <br /> hydrocarbons (PAHs) analysis. TPHd was non detect (ND) in the samples and the PAHs were <br /> ND with the exception of 0.012 pg/L J naphthalene reported in the MW-5 sample (the method <br /> California Environmental Protection Agency <br /> Zp� Recv led Paper <br />