SITE INFORMATION AND CORRESPONDENCE_FILE 3

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Ranbec ADDENDUM TO JULY 8,2010 WORK PLAN FOR MONITORING WELL DESTRUCTION AND REPLACEMENT AND ADDITIONAL PATH FORWARD Former Thrifty No. 172/ConocoPhillips No.5449 September 23,2010 additional wells being impacted by the new building, the accelerated redevelopment schedule, the construction of existing vapor extraction well clusters in relationship to current groundwater levels, the submerged well screens in the majority of groundwater monitoring wells, and the results of recent soil vapor extraction testing, Stantec proposes to properly destroy most existing onsite wells with the exception of wells MW-3, MW-7, and MW-12R; install one shallow offsite well near MW-6 to obtain a better understanding of the offsite plume; and install three other initial shallow onsite wells (including the already approved replacement of MW-4) and one deep onsite well once redevelopment activities are completed. The proposed scope of work is described below. Additional assessment may be required once the data is obtained from these new wells, and will be proposed if necessary at that time. The human health risk assessment required for this site will be proposed after data is available from the additional assessment. The fourth quarter 2010 groundwater monitoring and sampling event will be performed on October 4, 1020, prior to well destruction activities. 1.0 PROPOSED SCOPE OF WORK 1.1.1 Site Health and Safety Plan As required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910.120), and by the California Occupational Health and Safety Administration (Cal-OSHA) "Hazardous Waste Operations and Emergency Response" guidelines (CCR Title 8, Section 5192), Stantec will prepare a site-specific HASP prior to the commencement of fieldwork. The HASP will be reviewed by the field staff and contractors before beginning field operations at the site. 1.1.2 Permitting Well permits will be obtained from the San Joaquin County Environmental Health Department and City of Stockton prior to the commencement of drilling activities. Permits for the new wells will be obtained within two weeks of the opening of the new store at the site. 1.1.3 Utility Clearance Prior to scheduled field work activities, Stantec will mark the locations of the wells to be destroyed, protected, and installed in accordance with USA guidelines. Stantec will contact USA North no less than 2 days prior to the start of field work to allow USA members to mark out subsurface utility locations. Additionally, Stantec will contact a private utility locator to confirm the locations of marked USA member utility lines and investigate the presence of utility lines that are not owned or operated by USA members. The top 5 feet of the subsurface will be removed from the well locations using a pressurized air lance and vacuum rig or a hand auger, in order to minimize damage to subsurface utility lines that could not be located using conventional methods. 1.1.4 Destruction of Monitoring Wells and Vapor Wells Stantec will contract a C-57 California licensed drilling company to destroy MW-4, MW-10, MW- 11 R, VW-1, VW-3, VW-4(A,B,C), VW-5(A,B,C), and VW-6(A,B,C). Monitoring wells MW-4, MW- 10, and MW-11R and vapor wells VW-1, VW-3, VW-4(A,B,C), VW-5(A,B,C), and VW-6(A,B,C) were originally constructed of 2-inch PVC within 8-inch boreholes, and will be destroyed by overdrilling to the total depths with 10 to 12-inch hollow stem augers (HSA) and removing the well materials. The open boreholes will then be filled with bentonite slurry. The traffic rated well