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1. 0 METHODS 1. 1 Soil Sam lin Soil borings and soil sampling was performed under the direction of a State of California registered professional engineer. The soil borings were advanced using a truck-mounted hollow-stem auger drilling rig. To reduce the possibility of cross-contamination between boreholes, all downhole drilling equipment was steamed cleaned between each boring. To reduce cross-contamination between ' samples, the split-barrel sampler was washed in a soap solution and double-rinsed between each sampling event. 1 Soil sampling was 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 5 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 was placed into a glass jar and sealed for later screening with a PID/OVA. Another portion of the soil sample was used for classification and description. that part of the soil sample collected in a brass 10 tube within the California-type sampler was placed in sealed ice chest containing ice for transport to the laboratory. ' 1.2 Soil Classification As the samples were obtained In the field, they were classified by the engineer or geologist in accordance with the Unified Soil ' Classification System (USCS) . Representative portions of the samples were then returned to the laboratory 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 ' were also made. 1. 3 Soil-Sample Screening: Portable Photoionization Detector Method ' After soil sample jars were brought to ambient temperature, the head space of the soil sample jars was 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 was opened and the detector probe immediately placed within the head space of the jar. The highest observed reading was recorded. 1. 4 Monitoring Well Gravel Pack and Slot Size Selection The size of the gravel pack that was placed adjacent to the well screen was determined by the project manager, based on an estimation of the distribution of grain size in the formation ' which was likely to be encountered within the uppermost saturated