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April 7, 19 92 <br />. <br /> ARCO Station No 2168, Stockton, California <br /> extraction wells based on PID readings <br /> o Drill one 8-inch-diameter soil boring near the waste-oil tank cavity If odor <br /> or soil discoloration is noted in soil within 10 feet of ground water, the boring <br /> may be reamed to a 10-inch-diameter boring and converted to a 4-inch- <br /> diameter ground-water monitoring well. <br /> o Drill three 10-inch-diameter soil borings to 10 feet below ground water <br /> (approximately 55 feet below grade) or 5 feet into the first aquitard and <br /> convert the bonngs into ground-water monitoring wells The proposed <br /> locations of soil borings and ground-water/vapor-extraction wells are shown <br /> on Plate 2 <br /> o Collect relatively undisturbed soil samples at 5-foot intervals or lithological <br /> changes from the ground surface to the total depth of each boring Soil <br /> samples will be placed in iced storage and maintained at 4 degrees centigrade <br /> for transport to the analytical laboratory <br />• o Develop, purge, and sample the ground-water monitoring wells <br /> o Submit water and appropriate soil samples to a laboratory approved by <br /> ARCO Soil samples will be selected in an attempt to delineate hydrocarbons <br /> vertically <br /> o Soil and water samples were analyzed for total petroleum hydrocarbons as <br /> gasoline (TPHg) using Environmental Protection Agency (EPA) preparation <br /> Method 5030 and modified EPA Method 8015 and benzene, toluene, <br /> ethylbenzene, and total xylene isomers (BTEX) using EPA Method 8020 <br /> Samples collected near the waste-oil tank will be analyzed for compounds <br /> recommended in the SJCPHS-EHD guidelines Soil samples from the bonngs <br /> having the highest reading on the PID will be analyzed for total lead using <br /> EPA Method 7421 If total lead is detected, we will discuss with ARCO the <br /> submittal of additional soil samples to delineate total lead in soil <br /> o Contract a licensed surveyor to survey the wells with respect to mean sea <br /> level <br /> o Evaluate the ground-water gradient beneath the site <br /> i <br /> 310094W 3 <br />