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California Regional Water Quality Control Board <br /> ;. <br /> Central Valley Region <br /> Karl E. Longley,SCD, PE,Chair � P <br /> Linda S.Adams Arnold <br /> Secrernrn-for Fresno Branch Office Schwarzenegger <br /> F_zrr�irrrezrnl I685 F Street,Fresno,California 937U6 Governor <br /> Protection (559)445-5116-Fax(539)445-5910 <br /> htt p:/lw�vw.ilial er b oar ds.ca.g ov/ce n t ra l v a l l ey <br /> 16 August 2007 <br /> RE AEl En <br /> M. Scott Mansholt ,,'" AUG 2 12007 <br /> Chevron Environmental Management Company <br /> 6001 Bollinger Canyon Road <br /> Rm K2066 ChmmEnvironmentalMamgeMnlCa. <br /> San Ramon, CA 94583-2324 <br /> REVIEW OF SECOND QUARTER 2007 GROUNDWATER MONITORING AND SAMPLING <br /> REPORT— US CAN - WELTY ROAD PROPERTY, VERNALIS, SAN JOAQUIN COUNTY <br /> Regional Water Board staff has reviewed the referenced groundwater sampling report, dated <br /> 26 July 2007 prepared for Chevron by Science Applications International Corporation (SAIC). <br /> The historical Old Valley Pipeline (OUP) and Tidewater Associated Oil Company (TAOC) <br /> pipelines, formerly owned/operated by predecessors of Chevron, were located along the <br /> northeast side of the US Can property. The former Vernalis Pump Station site (Bellini and <br /> Arcos properties) is located adjacent to the south-southeast of US Can. <br /> Six monitoring wells (MWs; two offsite and four onsite) associated with this site have been <br /> monitored irregularly since 1999 and on a quarterly basis since early 2005. The recent <br /> monitoring and sampling event was completed 30 April 2007. <br /> Two onsite wells (MW-1 and 2) contain a petroleum sheen and are not sampled (petroleum- <br /> adsorbing devices are used in these wells) and the other two onsite wells (MW-3 and 4) did <br /> not have sufficient water for sampling. The two offsite wells, MW-5 (installed in 2005) and <br /> VVFSMVV-1 (Western Farm Services monitoring well) contained sufficient water and were <br /> sampled. Groundwater flow is easterly at an approximate gradient of 0.001 ft/ft. Depth to <br /> water is between 32 and 36 feet. <br /> Samples were submitted for total petroleum hydrocarbons as diesel (TPHd) and polynuclear <br /> aromatic hydrocarbons (PAHs) analysis. TPHd was ND for MW-5 and 630 pglL for the <br /> WFSMW-1 sample. PAHs were ND in both samples except for naphthalene at 0.014J pglL <br /> and 0.032J pg/L, respectively in MW-5 and WFSMW-1; the method detection limit for <br /> naphthalene is 0.010 pg/L. These low concentrations are below the Environmental Screening <br /> Level of 17 pglL for naphthalene. <br /> The sample from WFSMWWI was split for analysis and sent to two different laboratories for <br /> analysis of the petroleum hydrocarbons of concern related to the site; a portion was sent to <br /> Chevron Energy Technology Company (ETC) for fuel fingerprint analysis. The different <br /> laboratories analyzed the same sample to evaluate if the THPd results and the fuel fingerprint <br /> California Environmental Protection Agency <br /> 0 Recpcled Paper <br />