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Work Plan to Delineate Soil Contamination in the Ag Chem Area ARCADIS Former Occidental Chemical Corporation Lathrop, California 3.2 Field Activities 3.2.1 Ag Chem Area Survey Prior to advancing soil borings,ARCADIS will contract with a licensed land surveyor to physically mark the boundaries of the areas of interest on the pavement at the site, using the legal description of the two Ag Chem Area areas of interest. Both legal descriptions are referenced to the northwest corner of Parcel A,as shown in Book 5 of parcel maps,on page 188 of the San Joaquin County records. A copy of the legal description,which was used as the basis for Exhibit G of the Voluntary Cleanup Agreement, is included as Appendix A. In addition, survey or global positioning system(GPS)coordinates of adjacent landmarks will be collected (e.g.,the railroad spur, corners of nearby buildings). These will facilitate the preparation of accurately scaled figures for subsequent Ag Chem Area reports. 3.2.2 Soil Sampling Soil borings will be advanced using direct-push drilling technology(DPT). Proposed soil boring locations are shown on Figures 4 through 6. Near the former UST area, all soil boring work will be conducted at least 25 feet from the active railroad spur, per ARCADIS health and safety requirements. Soil samples will be collected from each of the borings at approximately 2, 5 and 8 ft bgs (note that the water table is approximately 15 ft bgs). Each soil sample will be analyzed for DBCP, EDB, sulfolane, OCPs, OPPs and BHC isomers by APPL, Inc. laboratory of Clovis, California (APPL) on a standard turnaround time basis. Method detection limits will be below California Human Health Screening Levels (CHHSLs) based on unrestricted use(residential exposure scenario) (Table 4). Actual sample depths will vary depending on the depth of first encountered soil beneath asphalt during the field activities. Soil boring locations will be surveyed in the field using a handheld GPS device. The SOP for soil drilling and sample collection provides the necessary equipment and sampling and documentation procedures and is included as Appendix B. Sample results will be compared to CHHSLs in order to approximately delineate the extent of contamination exceeding residential screening levels within the boundary of the areas of interest.After analyzing laboratory results, additional borings will be advanced in a 10-ft step-out grid pattern and additional soil samples will be collected and analyzed until sample results are below CHHSLs. Subsequent field mobilizations will be conducted as needed in order to complete this task.Areas where contamination is detected above CHHSLs at 8 ft bgs will be addressed by collecting a deeper sample lamropmrk plan supplemental invest ag chem 05012012 c x 6