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California Regional Water Quality Control Board <br /> Central Valley Region <br /> Karl E. Longley,ScD, PE, Cliair <br /> Linda S.Adams Arnold <br /> Secrelaryfor Fresno Branch Office Schwarxenegger <br /> Envirenmeneal 1685 E Street.Fresno,California 93706 Governor <br /> Prorecrion (559)445-5116•Fax(559)445-5910 <br /> hltp:lh4�«v.rsterb aards.ca.eovlcent ralvalley <br /> 11 October 2007 RECEIVED <br /> OCT 1 5 2007 <br /> M. Scott Mansholt <br /> Chevron Environmental Management Company ChavmnEmft mentatMwagernarntCO- <br /> 6001 Bollinger Canyon Road <br /> Rm K2066 <br /> San Ramon, CA 94583-2324 <br /> REVIEW OF WELL ABANDONMENT AND SOIL AND GROUNDWATER INVESTIGATION <br /> WORKPLAN, US CAN -WELTY ROAD PROPERTY, VERNALIS, SAN JOAQUIN COUNTY <br /> Regional Water Board staff has reviewed the referenced groundwater sampling report, dated <br /> 28 September 2007 prepared for Chevron by Science Applications International Corporation <br /> (SAIL). The historical Old Valley Pipeline (OVP) and Tidewater Associated Oil Company <br /> (TAOC) pipelines, formerly owned/operated by predecessors of Chevron, were located along <br /> the northeast side of the US Can property. <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 two onsite <br /> wells (MW-1 and 2) contain a petroleum sheen and are not sampled; petroleum-adsorbing <br /> devices used in these wells are exchanged annually. Two onsite wells, MVI!-3 and 4 have not <br /> had sufficient water for sampling for some time. The offsite wells, MW-5 (installed in 2005) <br /> and WFSMW-1 (Western Farm Services monitoring well) were sampled at the same time. <br /> Groundwater flow is easterly at an approximate gradient of 0.401 ft/ft-, depth to groundwater is <br /> between 32 and 36 feet. <br /> SAIC's workplan proposes the following: <br /> ■ Prior to destroying MW-3, MW-4 and MW-5, provided adequate water is available <br /> and/or site access is granted, obtain groundwater samples and submit for analysis of <br /> the site petroleum hydrocarbon constituents of concern. If the results are ND (non <br /> detect) or do not exceed the Water Quality Objectives (WQOs) and the respective <br /> Environmental Screening Levels (ESLs), the wells will be properly destroyed; <br /> Advance six soil borings in data gap areas up and downgradient of MW-2 and advance <br /> five borings up and downgradient of former boring S13-17, east of MW-3. Soil and <br /> groundwater samples will be collected for analysis unless free phase crude oil is <br /> encountered. Offset borings are anticipated for those areas; <br /> California Environinental Protection Agency <br /> �.b� Recvcled Paper <br />