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1 <br /> Proposal for of Site Cleanup Confirmation May 5, 1992 <br /> Southland, 7-Eleven No 20680, 9110 Thornton Road, Stockton, CA 6 <br />' The Project Approach Flowchart (Figure 4) shows the work steps that will be implemented based on <br /> the results of the confirmation soil sample analyses As shown on this flowchart, different work steps <br />' will be implemented based on the sod results obtained <br />' 3.1 Soil Sampling and Analyses <br /> The first work step to be implemented will be the collection and analysis of soil samples from the on- <br /> site vadose zone The following section describes the basis for the proposed sample locations <br /> 3.1 1 Sample Locations <br /> Soil samples will be collected from the on-site vadose zone to confirm the remediation of the source <br /> area soils Sod samples will be collected from boring location points shown on Figure 5 These <br /> locations are based on the historic lateral extent of sod contamination and recent analytical data (i e , <br /> tank and line trench samples, samples from MW-20) The lateral extent of the hydrocarbon-impacted <br /> sod at the site was defined by collecting sod samples while drilling sod borings and analyzing the <br /> samples in the laboratory, and in the field using a portable photoionization detector (PID) Results of <br /> the PID screening and laboratory analyses indicated that petroleum hydrocarbons were present in <br /> sod samples collected from borings MW-1, MW-2, MW-3, MW-4, and MW-9 at depths ranging from <br /> near surface grade to approximately 35 feet below grade Cross sections A-A', B-B', and C-C' <br /> present the portable photoionization detector (PID) readings and laboratory analytical results of the <br /> sod samples (Figures 6, 7, and 8) The locations of the cross sections are shown on Figure 9 <br /> Based on the PID readings and analytical results presented on the cross sections, borings A, B, C, <br /> D, E, F, G, H, and I will be drilled to confirm cleanup of the vadose zone sods as follows <br /> ■ Locations A, B, and I will confirm cleanup of the western edge of the historic <br /> plume <br /> ■ Locations I and H will confirm cleanup of the northern edge of the historic plume <br /> 1 ■ Locations H and E will confirm cleanup of the eastern edge of the historic plume <br /> I ■ Locations E, F, and A will confirm cleanup of the southern edge of the historic <br /> plume <br /> ■ Locations C, D, and G will confirm cleanup in the center of the historic plume <br /> - 5'GROUNDWATER <br /> TECHNOLOGY, INC <br />