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08 September 2000 AGE -NC Project No. 97-0372 Page 15 of 18 The ground water samples will be recorded on a chain -of -custody form as described above for soil samples. The containers will be wrapped in paper towels and sealed in plastic bags. The packaged containers will be placed in a chilled ice -chest with the chain -of -custody form, which will also be sealed in a plastic bag. The chest will be filled with material to prevent unnecessary movement and possible marring or breaking of the sample containers. The sealed chest will be delivered directly by AGE personnel to a DHS -certified laboratory or will shipped via an overnight carrier as described above. 5.5. LABORATORY ANALYSIS OF SELECTED SOIL SAMPLES A minimum of one soil sample per boring will be analyzed for pH, total cyanides and the target metals according to the methods noted below. Additional samples may be analyzed based on initial results. Soil samples will be selected for laboratory analysis based on the highest probability of encountering the target analytes. The probability of a sample being impacted by a release of contaminants in the vadose zone is primarily dependant on: • Vertical proximity to the release; • Affinity for adhesion to soil types by the contaminants; • Existence of a viable migratory path from the suspected source to the soil; and • Volume of the release. Migration of contaminants in the vadose zone is primarily gravity driven with soil permeability guiding the downward migration path. Permeability barriers and natural diffusion will cause horizontal spreading of the contaminants during the downward migration. Intuitively, the soil underlying a point of release will most likely be impacted at the point of closest proximity to the release, hence proximity to the suspected points of release will be a primary consideration in selection of samples for analysis from the vadose zone. Soil composition plays an additional important role in migration and retention of contaminants; fine- grained soil, especially organic -rich fine-grained soil, will generally have lower permeability, unless fractured, and generally has a higher affinity for adsorption of most contaminants, especially metals and hydrocarbons. Clean, coarse-grained soil provides preferential pathways, but has a significantly lower adsorption capacity for most contaminants. Therefore, soil compositions will play a significant role in selection of samples for laboratory analysis, fine-grained soil in contact with overlying coarse- grained soil will be given high consideration in the sample selection process. Advanced Gco6nviron nental, Inc