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Work Plan Addendum - Third Quarter 2007 PACIFIC PRIDE -WEST LANE 3230 North West Lane, Stockton, California 1.0. INTRODUCTION At the request of Mr.David Atwater of Van De Pol Enterprises Inc.,Advanced GeoEnvironmental, Inc (AGE) has prepared this work plan addendum for the site located at 3230 North West Lane, Stockton,California(site).This work plan addendum was prepared in accordance with a San Joaquin County Environmental Health Department(SJCEHD)letter directive (Appendix A),dated 07 May 2007. The work plan provides the scope of work and procedures for(1) a soil vapor investigation around the perimeter of the former underground storage tank (UST) area and (2) additional assessment of 1,2-dichloroethane(1,2-DCA)impacted ground water that was recently detected from the southwest section of the site(i.e.wells MW-4 and MW-5R). The scope of work will include the advancement of three soil probe borings to depths of 5 feet below surface grade(bsg) for collection of soil-vapor samples; and the advancement of three soil borings to depths of 70 feet bsg for the collection of grab ground water samples for analysis. A summary of previous investigation for this site was included as Appendix A in Quarterly Report-2"d Quarter 2007,dated 20 August 2007.The location of the site is illustrated on Figure 1. A plan of the site is illustrated on Figure 2. The Central Valley Regional Water Quality Control Board (CVRWQCB) is now requiring evaluation of Environmental Screening Levels, California Human Health Screening Levels (CHHSLs)and evaluation for potential vapor intrusion into buildings prior to closure consideration. As a result,this work plan addendum for a vapor intrusion investigation and assessment of 1,2-DCA impacted ground water has been prepared in accordance with CVRWQCB guidelines for the investigation of underground storage tanks (UST) sites. 2.0. SCOPE OF WORK Due to shallow petroleum-impacted soil documented at the site during UST removal activities (February 1999), the SJCEHD has directed by letter (Appendix A; dated 07 May 2007), that the threat of potential vapor intrusion into buildings on the site should be investigated.Therefore,AGE is proposing to drill and sample three soil vapor probe borings (P-13 through P-15) at the site to characterize soil vapor intrusion. Additionally,due to the presence of 1,2-DCA at concentrations above the California Environmental Protection Agency(EPA)water quality goals method detection limit(MDL)of 0.5 µg/L,the EHD has stated by letter(dated 07 May 2007)that they can not consider this site for closure until the 1,2- DCA issue is resolved. Therefore, AGE is proposing that an additional three soil borings be advanced in the south section of the site and directly south off-site for further 1,2-DCA impact evaluation. Advanced GeoEnvironmental,Inc.