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y FIELD PROCEDURES FOR DRILLING AND SAMPLING AND GROUNDWATER MONITORING WELL INSTALLATION Drilling Procedures The soil borings were drilled using 8-inch-diameter, continuous-flight, hollow-stem augers. To avoid cross-contamination, drilling equipment in contact with potentially-contaminated material was decontaminated by steam cleaning before and after each use. Decontamination fluids were placed into properly-labeled Department of Transportation approved drums for disposal. Soil Sampling Procedures Prior to drilling, each boring was hand-augered to a minimum depth of 5 feet. During drilling, samples were collected beginning at 5 feet below grade and generally at 2-1/2-foot intervals to the total depth of each boring. The soil sample collected from MW-9 was collected with a hand sampler, which consisted of an 1-1/2-inch core barrel containing a stainless steel line that was driven using a slide hammer. Additional soil samples could not be collected due to overhead utilities which prevented raising the drilling rig mast. Before and after each use, the sampler was washed using a phosphate-free detergent followed by tap water and deionized water rinses. Soil sampling was accomplished using a California- = modified split-spoon sampler lined with appropriately- sized brass tubes. A 140-pound slide hammer falling 30 inches was used to advance the sampler 18 inches ahead of the hollow-stern augers into undisturbed soil, and blow counts were recorded for every 6 inches of penetration to measure soil density. After retrieval from the augers, the sampler was split, the sample tubes removed, and a soil sample was selected for possible chemical analysis. The sample was retained within the brass tube, and both ends were immediately covered with Teflon sheeting and polyurethane caps. The caps were sealed with tape and labeled with the following information: Alisto Engineering project number, boring number, sample depth interval, sampler's initials, and date of collection. The soil sample was immediately placed in a waterproof plastic bag and stored in a cooler containing blue or dry ice. Possession of the soil samples was documented from the field to a state-certified analytical laboratory by using a chain of custody form. Soil samples and drill cuttings, when appropriate, were described by Alisto Engineering personnel using the Unified Soils Classification System, and field estimates of soil type, color, moisture, density, and consistency were noted on the boring logs. The logs were reviewed by a civil engineer registered in the State of California. Groundwater Monitoring Well Installation Construction of the groundwater monitoring wells was based on the stratigraphy in the soil borings. The well construction materials were introduced into the boring through the hollow-stem augers to centralize the well casing and minimize the possibility of native material entering the annular space of the well.