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California Regional Water Quality Control Board <br /> Central Valley Region ; <br /> Karl F. Longley,SeO, P.L„Chair y <br /> Linda S.Adams 93706 Arnold <br /> F LE 168 E 55-51 FT,Fax <br /> California 5910 <br /> 5ecrerr«v f00' Sehwgrzenegger <br /> Erarirorrnerrlul � {579}045-51 Ib•fax[559J��15-591U Goverr�rz+ <br /> Prolecrian 115111 http ilFvww.��alerbuards.ca.govleenlral�,tilr� <br /> RECEIVED <br /> 12 November 2008 <br /> NOV 17 2008 <br /> M. Scott Mansholt Chum nvimmentalManagemenlCo, <br /> Chevron Envirorimental Management Company <br /> 5111 Ballinger Canyon Road <br /> Room 3432 <br /> San Ramon, CA 94583 <br /> REVIEW - SOIL AND GROUNDWATER INVESTIGATION REPORT AND ADDITIONAL <br /> INVESTIGATION WORKPLAN, MOUNTAIN HOUSE DEVELOPMENT SITE #6, MOUNTAIN <br /> HOUSE, SAN JOAQUIN COUNTY <br /> Chevron Environmental Management Company (Chevron) submitted a Soil and Groundwater <br /> Investigation Report with an Additional Investigation Workplan (Workplany dated 24 July 2008. <br /> for Mountain House Development Site #5 (Site). The Report and Workplan were prepared for <br /> Chevron by Science Applications International Corporation (SAIC)- The Site is at the <br /> intersection of West Byron Road and Wicklund Road, northwest of Tracy. Fallowing <br /> completion of the recent investigation, SAIC proposed that an additional soil and groundwater <br /> investigation be conducted. Detailed comments are provided in the attached memorandum <br /> and summarized below. <br /> The Site lies within the West Byron Road and Union Pacific Railroad (UPRR) right-of-way <br /> easements. The historical Old Valley Pipeline (OVP) is parallel, west of West Byron Road and <br /> the former Tidewater Associated Oil Company (TAOC) pipeline is between the road and the <br /> railroad tracks. Previously, a workplan dated 31 July 2007. to investigate the lateral and <br /> vertical extent of impacted soil and groundwater onsite and offsite to the east was approved. <br /> In March and April 2008, SAIC advanced borings and obtained samples for analysis to <br /> delineate crude oil affected soil and groundwater previously identified at the Site. According to <br /> the report, affected soil and groundwater was identified at three separate areas, designated <br /> Area 1 , 2, and 3. <br /> SAIC's Report concluded: <br /> • The lateral and vertical extent of affected groundwater has been defined in Area 1 The <br /> downgradient extent of affected soil has not been defined and an additional <br /> investigation is needed. <br /> • Within Area 2, the lateral extent of soil and groundwater has not been defined and <br /> additional investigation is needed downgradient to the east-northeast. <br /> • The lateral, downgradient extent of affected soil to the east-northeast in Area 3 is <br /> undefined and additional investigation is needed. <br /> Ca4furnia Environmental Protection A-ener <br /> i: Peci,cled Paper <br />