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0 Former Countryside Market,Stockton,California Feasibility Study and Interim Remedial Action Plan May 20,2013 6.0 VERTICAL PLUME DELINEATION ASSESSMENT In order to better assess the migration of plume constituents that have be ndetected in downgradient domestic wells (Section 2.3) and provide more detailed hydrogeological in ormation for assisting in the construction of test wells AS-1, AS-2, OBS-1 and VW-1 (Section 5.1), GI proposes to conduct the following tasks prior to any of the feasibility data collection activities detailed �n the preceding section. 6.1 Domestic Well Video Logging Video logging of domestic well 10967 will first be conducted since construction details associated with this downgradient well that has been equipped with a treatment system (SGI's February 22, 2012 Wellhead Treatment Memorandum) are not available. The video logging results will be used to determine the screened interval and help evaluate the vertical extent of the plume. The video logging camera will be contained within a sealed casing and include a downhole light head, as well as a module that tilts under operator control to look both down the borehole and at the casing wall. The camera will also be pressure rated and resistant to vibrations and shock. Deployment of the contained camera will be achieved via a winch system powered by an electric motor and secured via a steel reinforced cable. 6.2 Cone Penetration Testing Once the above domestic well video logging activities are completed and the information is assimilated, high resolution site characterization data will be collected via the advancementm of two direct push cone penetration test borings at the approximate location shown on Figure 4 (CPT-1). This location was selected to obtain valuable soil stratigraphy data while minimizing the potantial for contaminants to be dragged down during boring advancement activities since it is in proximity to the former UST area but far enough downgradient to be outside of the primary release zone. The borings will be advanced a few feet apart with the initial boring used for detailed geologic profiling, and the final boring subsequently pushed to various target depths for discreet groundwater sampling based on the real-time and nearly continuous Iithologic data. Once effective vertical plume delineation is achieved, the data may also be utilized to potentially modify the test well (AS-1, AS-2, OBS-1 and VW-1) construction details (Section 5.1). Based on the attached domestic well boring log (Appendix A), each boring will likely be advanced to a maximum depth of approximately 135 to 140 feet bgs, as feasible, such that the significant clay layer that is present below this depth is not penetrated. This depth may be modified based on the domestic well video logging results and/or Iithologic data collected during boring advancement activities. The boring data will be compiled, analyzed and integrated into the feasibility testing plan (Section 5.0) and subsequent IRAP (Section 7.0). Feasibility Study an Ireasibility Study&I RAP Tet Fnal. w 6-1 The Source Group,Inc.