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IfIN/CN+lEANEA Mr. Charles Leubner 6 February 1998 Page 4 Soil borings at the former underground gasoline tank site will also be drilled to a depth of 35 feet below ground surface to evaluate the vertical and lateral extent of gasoline range hydrocarbons. At a minimum, three soil samples from each boring will be submitted for laboratory analysis. The three samples will be for the 15-foot depth,the 35••foot depth(or deepest sample collected), and one other sample that is the likeliest to contain high concentrations of hydrocarbons. Remote Fill Pipeline Soil samples will be collected using a hydraulically driven, 1-inch or 2-inch diameter continuous corer. Because it is not feasible to drill inside of the Bus Wash that is now located over the remote fill trench, the two soil borings at this area will be drilled at an approximate angle of 30 degrees from vertical. Soil samples will be collected at a minimum of 4-foot intervals for lithologic logging, field screening, and possible laboratory analyses by inserting PETG liners inside of the corer. To minimize the potential for cross-contamination, coring equipment and liners will be cleaned with a high-pressure hot water washer prior to drilling each boring. After the soil samples are collected, the soil borings will be backfilled with a neat cement grout in compliance with San Joaquin County regulations and requirements. The section of the liner containing the soil sample to be submitted to the laboratory for analysis will be sealed with Teflon sheets secured by plastic caps. The liner will then be labeled to indicate a unique sample number, the date and time collected, and the sampler's identification. The samples will be stored in an ice-chilled cooler for preservation during transport to a State-certified laboratory for analysis. Soil samples will also be described and logged using the Unified Soil Classification System and selected samples will be screened in the field for the presence of organic vapors. Rinse water will be stored in drums at the site for subsequent disposal. The two slant soil borings will be driven to a vertical depth below sample P17 of 15 to 20 feet below ground surface. The exact depth attained beneath P17 will depend on how close the borings can be located to the Bus Wash building footings and the angle at which the Geoprobe will be driven. All soil borings will be backfilled with a neat cement grout according to San Joaquin County regulations Qualitative Field Screening To provide a preliminary indication of possible contamination, a portable organic vapor detector will be used to monitor for the presence of organic vapors in soil collected from the borings. This field screening method consists of filling a Zip Lock plastic bag to about one-third it's capacity with soil and sealing the container. After allowing sufficient time for the soil vapor to equilibrate with headspace, the bag will be opened enough to allow for insertion of an organic vapor analyzer