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METHODS Soil Sampling Soil borings and soil sampling will be performed under the direction of a State of California registered professional engineer or geologist. The soil borings will be advanced to a depth of approximately five below grade by using a hand auger. The soil borings will be advanced, below five feet to final depth, using a truck-mounted hollow-stem auger drilling rig. To reduce the possibility of cross-contamination between boreholes, all downhole drilling equipment will be steamed cleaned between each boring. To reduce cross-contamination between samples, the split-barrel sampler will be washed in a soap solution and double- rinsed between each sampling event. Soil sampling will be done in accordance with ASTM 1586-84. Using this procedure, a two-inch O.D. split-barrel sampler or a two-inch I.D. California-type sampler is driven into the soil by a 140-pound weight falling 30 inches. After an initial set of 6 inches, the number of blows required to drive the sampler an additional 12 inches is known as penetration resistance, 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 will be placed into a glass jar and sealed for later screening with a PID/OVA. Another portion of the soil sample will be used for class- ification and description. That part of the soil sample collected in a brass tube within the California-type sampler will be stored at approximately 4° C for transport to the laboratory. Soil Classification .r As the samples are obtained in the field, they are classified by the engineer or geologist in accordance with the Unified Soil Classification System (USCS). Representative portions — of the samples are then returned to the laboratory for further examination and for verification of the field classification. Logs of the borings indicating the depth and iden- tification of the various strata, the N value, and pertinent information regarding the method of maintaining and advancing the borehole are also made. Soil Sample Screening: Portable Photoionization Detector Method After soil sample jars have been brought to ambient temperature, the head space of the y soil sample jars will be screened with a portable photoionization detector equipped with a 10.2 eV lamp calibrated to benzene for direct reading in ppm. The sample jar lid will be opened and the detector probe immediately placed within the head space of the jar. The highest observed reading will be recorded.