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max , M _ 1Q 11 D 1 Soil Sampling and Contamination Redijetion Soil borings and soil sampling were performed under the direction of a Delta engineer or geologist. The soil borings were advanced using a truck-mounted hollow-stem auger drill rig. To reduce the chances of cross-contamination between boreholes, all downhole drillin g equipment was steamed-cleaned between each boring. To reduce cross-contamination between samples, the split-barrel sampler was washed in a soap solution and a double-rinsed between each sampling event. Soil sampling was done in accordance with ASTM 1586-84. Using this procedure,a 2-inch outside-diameter split-barrel sampler or a 2-inch''f-wide-diameter California-type sampler is driven into the soil by a 140-pound weight falling 30 inches. After an initial set of 6 incLws,,:,-number of blows required to drive the sampler an additional 12 inches is known as penetration re.^istance,or the "N" value. The N value is used as an empirical measure of the relative density of cohesionless soils and the consistency of cohesive soils. Upon recovery,a portion of the soil sample was placed into a plastic bag and sealed for later screening with a photelon!zationdetector. Another portion of the soil sample was used for classification and description. F r That part of the soil sample collected in brass tubes within the California-type sampler was stored at i approximateiy 4°C for transport to the laboratory. '�' 2 iI 1 ill io - As the samples were obtained in the field, they were classified by the crew chief/geologist in accordance I with the United Soil Classification System (USCS). Representative portions of the samples were then .. retained for further examination and for verification of the field classification, Logs of the borings indicating the depth and identification of the various strata, the N value, and pertinent information regarding the method of maintaining and advancing the borehole will be made.' 1.3 8oij:&rmjIe-S9rMingIhNu Photdionization Detector Method After soil in the plastic bag were brought to ambient temperabire,the headspace vapors of the soil sample bags were screened with a portable photoioniration detector equipped with a 10.2 eV lamp calibrated to benzene. The sample bag was opened and the detector probe immediately placed within the headspace of the plastic bag. The highest observed reading was recorded.