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Stantec Consulting Corporation <br /> 3017 Kilgore Road Suite 100 <br /> Stantec Rancho Cordova CA 95670 <br /> Tel:(916)861-0400 <br /> Fax:(916)861-0430 <br /> September 23, 2010 <br /> Mr. Mike Infurna <br /> San Joaquin County Environmental Health Department <br /> 600 East Main Street <br /> Stockton, California 95202 <br /> RE: Addendum to July 8, 2010 Work Plan for Monitoring Well Destruction and <br /> Replacement, and Additional Path Forward <br /> Former Thrifty Oil Co. Station No. 172 <br /> ConocoPhillips Site No. 5449 <br /> 7647 Pacific Avenue, Stockton, California <br /> Dear Mr. Infurna: <br /> This letter, prepared by Stantec Consulting Corporation (Stantec), on behalf of ConocoPhillips <br /> (COP), addends the original Work Plan for Monitoring Well Destruction and Replacement, dated <br /> July 8, 2010, for ConocoPhillips Site No. 5449, located at 7647 Pacific Avenue, Stockton, <br /> California (Figure 1). When Stantec recently learned that the redevelopment schedule was <br /> being accelerated (Attachment 1), we contacted the San Joaquin County Environmental Health <br /> Department (SJCEHD) regarding the change in plans. Mr. Nuel Henderson, Jr. of the SJCEHD <br /> requested that we document the changed plans, and propose a new path forward. This work <br /> plan addendum is intended to fulfill the request of the SJCEHD. Work plans for characterization <br /> of the vertical extent of impacted soil in the saturated zone, and lateral delineation of impacted <br /> groundwater, have also been requested in correspondence from the SJCEHD dated September <br /> 2, 2010. This work plan proposes assessment to help accomplish these goals, and further <br /> recommendations will be made after data from the proposed assessment is available. <br /> At the time of the change in redevelopment plans, Stantec was preparing to begin interim <br /> groundwater remediation in accordance with SJCEHD's September 2, 2010 approval of the <br /> Interim Remediation Action Plan dated August 27, 2010. Because the time before <br /> redevelopment has been shortened, Stantec proposes that interim remediation be postponed at <br /> this time in preparation for the site demolition. The remediation system will be removed and <br /> stored offsite, and the conveyance piping and conduit will be cut at the well boxes prior to <br /> redevelopment activities. The accelerated redevelopment schedule will allow Stantec to begin <br /> permanent remediation sooner than anticipated. <br /> As part of the work plan dated July 8, 2010, Stantec originally proposed to destroy monitoring <br /> well MW-4 because it would be impacted by the expansion of the current building, and replace it <br /> with well MW-4R (Figure 2). Revisions to the redevelopment plans have since been made, and <br /> two additional wells (MW-11 R and VW-3) will be impacted by the building expansion. Due to <br />