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Environmental <br /> Resources <br /> Management <br /> FC-D)E� 2525 Natomas Park Drive <br /> �C Suite 350 <br /> Sacramento,CA 95833 <br /> S D p t 0 2Q06 (916)924-9378 <br /> 3 January 2006 (916)920-9378(fax) <br /> ENUiR0M;E11T HEALTH <br /> PERMIT/SERVICES <br /> Mr. Marcus Pierce <br /> Regional Water Quality Control Board <br /> Central Valley Region Lb <br /> Sun Center Drive #200 ERM, <br /> Rancho Cordova, CA 95670-6114 <br /> Subject: Rebound and Remediation Effectiveness <br /> Evaluation Addendum Workplan <br /> Former Tracy Maintenance Facility <br /> Union Pacific Railroad Company <br /> Tracy, California <br /> Dear Mr. Pierce: <br /> On behalf of Union Pacific Railroad Company (UPRR), ERM-West, Inc. <br /> (ERM) is pleased to submit this requested workplan to the Central Valley <br /> Regional Water Quality Control Board (RWQCB). This workplan has <br /> been prepared to assess the current concentrations of residual volatile <br /> organic compounds (VOCs) in the source area, as requested in the <br /> RWQCB's 6 October 2005 response letter to the 2004/2005 Annual <br /> Monitoring Report. This work is being completed as an addendum to the <br /> Rebound and Remediation Effectiveness Evaluation (2003 Evaluation) <br /> submitted to the RWQCB in April 2003. <br /> INTRODUCTION <br /> The objectives of the remedial actions performed at the site have been to <br /> remove VOCs from the soil and ground water and recover free-phase <br /> diesel product at the site. To remediate the VOCs, UPRR has constructed <br /> and operated a soil vapor and ground water extraction system <br /> (dual-phase system)within the source area. This system has also assisted <br /> in the recovery of diesel product. The primary diesel recovery technique <br /> has been the placement of adsorbent socks in the impacted wells. Prior <br /> to implementation of the dual-phase system, as an interim measure to <br /> control the off-site migration of VOCs, UPRR constructed a ground water <br /> extraction system (margin well system) at the downgradient property <br /> boundary. <br />