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M <br /> " c � <br /> r <br /> t <br /> ` 3 SU1lL BORINGS <br /> i . <br /> Six exploratory soil borings were drilled at the site on May 29 and 30, 1990. Three of the <br /> borings were drilled to a depth of 25 feet and were later converted to groundwater <br /> monitoring wells. A fourth boring was drilled down to a depth of approximately 11 feet <br /> i , <br /> just above the water table. The remaining two borings were drilled at a 60' angle under <br /> an abandoned 500 gallon underground leaded gasoline tank. The location of the six <br /> borings is shown in Figure 3. <br /> Borehole drilling and sampling operations was accomplished using a truck-mounted hollow <br /> stem auger drill rig. The three borings which were converted to monitoring wells were <br /> drilled to approximately 10 feet below the water table to accommodate a. 15-foot well <br /> ' screen. The entire length of the borehole was continuously logged for the purpose of <br /> describing the vertical variations in the soil profile encountered. Soil samples for <br /> laboratory analysis were collected at five (5) foot intervals. All samples collected were <br /> .: submitted for chemical analysis. In accordance with general Regional Water Quality <br /> - Control Board (RWQCB) requirements, one sample from each borehole was collected <br /> :nom directly above the groundwater interface. <br /> In accordance with San Joaquin County Department of Health and RWQCB practices, an <br /> soil cuttings generated by the borehole drilling and sampling operations were contained and <br /> stored on-site. However, since subsequent analysis has shown that this material contains <br /> no detectable levels of petroleum hydrocarbon or purgeable haIocarbon compounds,these <br /> cuttings will be used to back-fill the proposed re-excavation. The two angle borings were <br /> drilled at an angle of 60• from the horizontal. Soil samples were collected at 7 and 12 <br /> foot intervals in AB-1, and 9 and 13 foot intervals in AB-2 corresponding to vertical depths <br /> of 6 and 10 feet respectively in each boring. These borehole configurations enabled soil <br /> samples to be collected at the base of the tank and at a depth of approximately 4 feet, <br /> immediately beneath the tank in each boring, <br /> 6 <br />