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1 Proposal for of Site Cleanup Confirmation May 5, 1992 Southland, 7-Eleven No 20680, 9110 Thornton Road, Stockton, CA 7 ' Because groundwater elevations have decreased by approximately 20 feet at the site, the confirmation of remediation throughout the vertical profile is a critical step Groundwater ' Technology proposes that Fmples he collected-at 5-foot intervals._ai eich bong tocatio Varying in the first sample collection depth so that samples representative of various depths are collected To ' achieve this goal, soil sample collection will begin at a depth of 2 feet for bonngs A, I, E, and D, soil sample collection will begin at a depth of 5 feet for borings B, C, F, G, and H Sampling will cL ue_to a-gepth of-45-feet or until the groundwater Is encountered, whichever occurs first 3 1 2 Soni Sample Collection and Field Screening Methodology ' The borings will be drilled using 8 0-inch outside diameter, truck mounted, hollow-stem auger equipment Soil samples will be collected using a California split-spoon sampling device lined with ' three, 6-inch brass tubes Each brass tube representative of the first 6 inches will be capped, taped, labeled, and placed on ice for possible laboratory analysis The contents of the middle brass tube ' will be extruded into a plastic bag for field screening using a hand-held PID After the PID reading is recorded, the contents of the bag will be used for lithologic description, After the samples have been collected, the borings will be sealed in compliance with SJPH g p requirements 3 1 3 Soil Sample Selection and Analyses Samples will be selected for analysis as follows I ■ If PID readings of greater than 10 ppmv are detected in four or more samples per boring, the sample with the highest PID level will be analyzed for BTEX and TPH-as- gasoline on a 48-hour turn-around and the shallowest and deepest samples with a PID reading greater than 10 ppmv will be retained for possible analysis (all lead and EDS analyses will be done on standard turn-around times) The two samples on hold will then be analyzed if the first sample contains TPH-as-gasoline greater than 10 ppm These samples will be analyzed on a standard turn-around time ■ If three or fewer samples have PID readings exceeding 10 ppmv, the sample with the highest PID reading will be analyzed on standard turnaround time I �—': GROUNDWATER TECHNOLOGY INC