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Rf1MlCI-HIRNIN Mr. Charles Leubner 6 February 1.998 Page 2 After presenting the results of the underground storage tank excavation to PHSIEHD in the Helmick and Lerner Inc. report entitled Tank Re oval Report- Edison High School Stockton, California dated 30 January 1994, the County requested a soil investigation to determine the vertical extent of contamination in soil and, if encountered, groundwater. SCOPE OF WORK Task 1—Conduct Soil Borings . Because the 2-foot thick, concrete anchor slab at the base of the tank excavation was not removed prior to the tank hole being backfilled with pea gravel, a single boring located directly over the former tank site is not feasible. As an alternative, two slant borings are proposed at the-- locations shown on Figure 2. Since the most significant contaminate wno —a-s de-tected at th orth end of the tank, these borings will focus on this aur a of the excavation. The slant borings will be drilled using the Geoprobe method of direct pen tration technology(DPT). Drilling activities will be conducted according to San Joaquin County regulations and permitting requirements. Drilling and Sam lin Soil samples will be collected using a hydraulicall y driven, 1-inch or 2-inch diameter continuous corer. Soil samples will be collected at a minim 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. Depending upon the angle of the boring and the dist jni he centerline of the tank,the borings will be drilled to a vertical depth of betwee 25 30 feet belowound surf ca e ta-evaluate the vertical extent of diesel range hydrocarbons. At a minimum, three_ soil sarnDles from each boring will be submitted for laboratory analysis. The three samples will be from the 15-foot depth, 30-foot i