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r. METHODS AND PRG.EDURES a The following sections describe the methods and procedures used for: The installation of the exploratory soil borings and well borings; discrete soil sampling; well installation and development; and groundwater sampling. Bore Hole Drillin On June 24, 1991, three soil borings MW-1, MW-2, and NW-3, were drilled for subsequent conversion into 2-inch outside diameter (OD) groundwater monitoring wells. MW-1 was drilled immediately adjacent to the previously removed underground waste oil tank, MW-3 was drilled near the southeastern corner of the property in order to assess the possibility of groundwater contamination coming from an off site source, and MW-2 was drilled near the northeastern corner of the property to allow for a three point groundwater elevation survey to determine the direction and gradient 'of groundwater flow (Figure 2, Site Characterization Map) . The borings were drilled by Exploration Geoservices of San Jose, California, a State-licensed C-57 well contractor. These soil borings were drilled using a B-56 Mobile Drilling Rig using 8-inch OD continuous flight hollow-stem augers. The borings were initially advanced to the depth of groundwater (approximately 9-1/2 feet below surface grade. The borings were then extended through 10 feet of aquifer material and were terminated at a depth of 20 feet below surface grade. On June 25, 1991, four exploratory soil borings, SB-1, SB-2, SA-3, and SB-4, were drilled along the perimeter of the previously removed underground waste oil tank (Figure 2, Site Characterization Map) . The soil borings were drilled using a 3-56 Mobile Drilling Rig using 8-inch hollow-stem augers. Each boring was drilled to a depth directly above the saturated zone, which was approximately 9- 1/2 feet below surface grade. Upon completion of each of the exploratory borings, they were subsequently back-filled with neat cement to surface grade. Environmental Health Specialist Linda A. Turkatte from the San Joaquin County Public Health Services visited the site on both days and briefly supervised the drilling procedures. A geologic boring log of each boring was maintained and are included in Appendix A, Soil Boring/Well Completion Logs. The logs include field descriptions of the soil properties, lithologic variations using the United Soil Classification System, penetration rate of the split-spoon sampler, moisture conditions, well construction details, and any unusual characteristics noted that indicated the presence of, hydrocarbon contamination. The logs are signed by a Registered professional. 275 GRANT LINE ROAD PAGE 8