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between each use and the drive sampler will be washed with a trisodium phosphate solution to limit the.potential for cross-contamination between uses. Drilling and sampling will be performed in accordance with ASTM Method D 1452-80, "Soil Investigation and Sampling by Auger Borings." For logging and analytical purposes, soil samples will be collected from each boring at five foot intervals beginning at ground surface. Additional samples may be collected at changes in lithology and intervals specified at the discretion of the field geologist. Samples will be collected by advancing the auger to a location immediately above the desired sampling depth and then driving a modified California split-spoon sampler lined with three brass tubes into the undisturbed soil. The sampler will be driven by a 140-1b hammer with a 30-inch drop (or an automatic hammer system with an equivalent force) in accordance with ASTM Methods D 1586-84 "Split Barrel Sampling of Soil." Blow counts will be recorded in six-inch intervals after every sampling event. The ends of the bottom brass tube will be sealed using Teflon sheeting secured by tight fitting plastic caps. The brass tubes will be labeled with a unique sample number, date and time sampled, sampler's identification, and placed in a chilled ice chest for preservation. The contents of the remaining brass tubes will be used for developing descriptions of soil characteristics and for qualitative field screening. Each soil sample will be classified in accordance with the Unified Soil Classification System as described in the ASTM Standard D 2488-84 "Description and Identification of Soils (Visual-Manual Procedure)". Selected samples will be delivered with Chain-of-Custody forms to Sequoia Analytical Laboratory in Sacramento, a State- certified laboratory,for analysis. After sampling, 2-inch diameter monitoring wells will be constructed in each soil boring. Approximately 10 feet of 2-inch diameter, PVC well screen will be placed at the bottom of each monitoring well. The top of the well screen will be located adjacent to the depth where groundwater was first noted during drilling. For this project, monitoring well screens will not be extended into the vadose zone to minimize the potential for cross-contamination resulting from breaching potential confining layers of the shallow aquifer. Augers and associated drilling and well construction equipment will be cleaned with a high pressure hot water washer prior to drilling each boring. The sampling equipment and brass tubes will be cleaned with an Aiconox or trisodium phosphate wash and rinsed with distilled water prior to collecting each soil sample. Qualitative J'ield Screexiing To provide a preliminary indication of possible hydrocarbon contamination, a portable organic vapor detector will be used to monitor for the presence of organic vapors in soil collected from the borings. This field screening method consists of filling a Zip Lock plastic bag to about one third capacity with soil and sealing the container. Amer approximately 15 minutes, the bag is opened enough to allow for insertion of the monitoring equipment probes. Field monitoring will be conducted using an organic vapor analyzer(OVA) equipped with a flame ionization detector(F1D) and an OVA equipped with a photoionization detector(PID). The concentration of organic vapors Alt Pure Chemical Company-Tracy Facility HELMICK& LERNER INC HLi 00907 Page 5 90*a SS2-1 ',JauJa_1/)131W1aH WOa_� Sc_b2891%60ET 01 LS:ST 96. 9T -inf