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• 0 ' Suffolane Remedial A nr11 Investigation Work Plan ARCAUIS Former Occidental Chemical Corporation Lathrop, California ' • Ground penetrating radar(GPR)or radio frequency detector(RFD) 4.2 Field Activities ' 4.2.1 Site Characterization ' Additional site characterization will be conducted in the shallow zone(above 90 feet bgs)to provide a better understanding of the interbedded nature of the site geology. ' Cone penetrometer testing(CPT)and continuous core logging will be completed in up to four locations to compliment the lithologic information obtained from the installation of wells PW 18 and PW26. ' CPT borings are proposed in the vicinity of well PW26 to identify potential zones of increased porosity and groundwater flow to consider during development of a remedial ' design. The CPT borings will be advanced using a direct-push drilling rig equipped with a cone penetrometer that will measure and record tip resistance, pore pressure,and friction of the encountered soils. , The proposed CPT borings will be co-located with as many as four proposed direct- push soil borings advanced to approximately 90 feet bgs. The lithologic description ' (including photos)will be collected from each of the co-located direct-push borings and used to"field truth"the CPT data. Proposed CPT and co-located direct-push boring locations are detailed on Figure 5 and summarized on Table 1. ' 4.2.2 Sulfolane Source Area Delineation To further characterize the extent of sulfolane impacts present in the vadose zone, up to nineteen(19)soil borings will be advariced in the vicinity of PW26. Soil borings will be advanced using direct-push drilling technology to the top of the water table (approximately 15 feet bgs). Proposed soil boring locations are detailed on Figure 4. , Three soil samples will be collected from each boring at 5 feet, 10 feet and 15 feet bgs (i.e.,the interval just above the water table)and analyzed for sulfolane by APPL, Inc. ' laboratory of Clovis, Califomia'(APPL)by APPL SOP ANASULF using a Gas Chromatograph/Mass Spectrometer(GC/MS)on a standard turnaround time basis. The actual sample depth will vary depending on the depth to first encountered ' groundwater during the field activities. Soil boring locations will be surveyed in the field using a handheld global positioning system(GPS)device.The SOP for soil boring and sample collection provides the necessary equipment and sampling and documentation ' procedures and is included in Appendix B. 1 8