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APPENDLY A FIELD PROCEDURES This appendix describes field procedures for the installation of on-site air sparging wells for ARCO Station 2093, Tracy, California. Borehole Drilling The wells will be drilled by a licensed drilling subcontractor using a truck-mounted, hollow-stem auger drilling rig equipped with 8- to 10-inch-diameter bits and drill stem. Borehole depths may be based on site conditions such as depth to water, topography, and depth to bedrock. Borehole cuttings will be temporarily placed on plastic sheeting and covered with plastic. The disposal of these cuttings is the responsibility of ARCO. To prevent cross contamination during drilling, all equipment will be steam-cleaned prior to and between use at each borehole. Soil Sampling During Drilling Soil samples will be collected during the drilling operations for three reasons: (1) for field identification of the borehole lithology, (2) for qualitative field screening for the presence of hydrocarbons, and (3) possible laboratory analysis. For purposes of collecting soil samples for lithologic identification, field screening, and possible laboratory analyses, each borehole will be sampled approximately every 5 feet. The soil samples will be examined in the field and classified according' to the Unified Soil Classification system. In addition to evaluating the borehole lithology, the soil cores will be screened in the field with a photoionization detector (PID) or similar instrument, and the relative permeability of the soil will be qualitatively estimated. The lithology, PID reading, and estimated permeability of each sample will be recorded on the borehole Iog next to the depth interval from which the sample was obtained. Field Activities The design and construction of the wells and field oversight will be the responsibility of a registered geologist or a professional engineer. Field activities will be directed on a day-by-day basis by an experienced field geologist. The field geologist will also be responsible for recording on the borehole logs or in the field notes all observations and measurements made during the drilling and sampling operations. �J Use or disclosure of data contained on this sheer is subject to the restriction specified at the beginning of this document. 75241REP0RT-%W4R K PLN