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Jonas & Associates Inc representative of subsurface conditions The vacuum pressure reading on the purging apparatus was recorded to evaluate soil permeability and provide a better understanding of sod vapor readings The samples were collected through a septum ' located immediately adjacent to the probe on the sampling apparatus Each sample was collected with a microsyringe and injected into a gas chromatograph for analysis (EA, 1987) Points were chosen on the four sides of the tank area toP ermit estimation of the ' directional migration, if any, of gasoline vapors In the course of the sampling day, four standards and three system blanks were run (EA, 1987) 22 Soil Investigation During two subsurface investigations performed from 1986 to 1988, soil samples were collected during the drilling of eight soil borings (see Figure 3-1) at ' approximately 5-foot intervals using a 2 5-inch inside diameters litspoon sampler containing three brass tube liners The sampler was driven 18 inches beyond the ' tip of the auger by a 140-pound hammer dropping 30 inches The number of blows was counted for each 6-inch interval the sampler was advanced The brass sample tubes were then quickly extracted from the sampler The ends of the samplers in the two brass tubes closest to the shoe of the sampler were examined by a geologist and logged according to the Unified Soil Classification System prior to being labeled, capped, sealed and placed on ice The soil collected in the brass tube farthest from ' the shoe was logged, placed in a glass airtight container, and held for headspace analysis To avoid cross contamination, the sampling equipment was cleaned with potable water and trisodium phosphate prior to collecting each sample After heating the glass sample containers until warm, headspace vapors were analyzed with a Thermoenvironmental 580A Organic Vapor Analyzer (OVA) The OVA was periodically calibrated to measure all of the ionizable hydrocarbons as if they were benzene, using a standard gas The results of these field analyses were noted on the drilling logs (Appendix C), and were used to select soil samples appropriate for laboratory analysis Two to four soil samples were selected from each boring for laboratory analysis, ' according to the following criteria (1) The sample collected closest to the encountered water table 1 (2) The sample collected five feet below the encountered water table (3) The sample with the highest apparent hydrocarbon concentration (4) The deepest sample with apparent presence of hydrocarbons 3 1