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w ���'�1t sa*x`r�?ea 3.:-" fid¢'`x'='y '��''-E'.4-»v <br /> rn tx br-Y ' "Mak <br /> d• :.. S' 4„ '�`+'^ `�` t F".''�q ,� <br /> i <br /> September 13. 1991 <br /> Unocal Station No. 6981, Stockton. California <br /> The number of blows required to drive the sampler each successive 6,inch inter.al will be <br /> counted and recorded on the field boring log to give an indication of soil consiste;.cy. <br /> Examples of the Field Boring Log,the Unified Soil Classification System,and Log of Boring <br /> are included in Appendix C to this work plan. <br /> Soil samples will be evaluated with a photoionization detector (PID), which measures <br /> hydrocarbon concentrations in the ambient air or headspace above the soil sample. Field <br /> instruments such as the PID can be useful for providing a preliminary assessment of the <br /> relative levels of hydrocarbon vapors. The IM does not detect concentrations of <br /> hydrocarbons with the same precision as laboratory analyses. Soil samples collected for <br /> possible chemical analysis will be promptly sealed with aluminum foil,plastic caps,and tape. <br /> They will then be labeled and placed in iced storage for transport to the analytical <br /> laboratory. A Chain of Custody Record will be initiated by the field geologist and will <br /> accompany the soil samples to the laboratory. An example of the Chain of Custody Record <br /> is also included in Appendix C to this work plan. <br /> Soil Borings/Monitoring Wells <br /> "f'he three 8-inch-diameter borings, B-6,B-7,and 13-8,to be completed as deeper monitoring <br /> wells, MW-6, MW-7, and POW-8, respectively. will be terminated at 75 feet below surface <br /> grade, or terminated approximately 15 feet into unconfined ground water. Ground water <br /> in the water-table aquifer was previously encountered between 50 and 55 feet below surface <br /> grade. but has not been present ;rt the five onsite monitoring wells since October 1990, <br /> presumably due to low recharge during recent drought conditions (Applied GeoSystems, <br /> pending). On the basis of information supplied by Unocal about the deptlr to ground water <br /> at a nearby site, we expect ground water to be encountered above 75 feet below surface <br /> grade. if ground water is not encountered above 75 feet below surface grade, we will <br /> - 39032-4w 10 <br />