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California egional Water Quality Cor of Board �� '� <br /> Central Valley Region ; <br /> Karl E. Longley,ScD, PE,Chair ���-�='`" <br /> Linda S.Adams Arnold <br /> Secretary for Fresno Branch Office Schwarzenegger <br /> Environmental 1685 E Street,Fresno,California 93706 Governor <br /> Protection (559)445-5 1 16•Fax(559)445-5910 <br /> littp://www.waterboards.ca.gov/centralva[ley <br /> 11 October 2007 <br /> OC r <br /> M. Scott Mansholt <br /> Chevron <br /> nCanyon Environmental agement Company <br /> 6001 Boller <br /> 9 yon Road <br /> ck✓l�SCrt <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 /> (SAIC). 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, MW-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 0.001 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 SB-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 Environmental Protection Agency <br /> �a� Recycled Paper <br />