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■�L`1:�`i11 HC ' 2.2 Delta Environmental Investigation On October 24, 1990, Delta Environmental collected three soil samples (HB-1, HB-2, and ' HB-3) from the UST excavation by advancing a hand auger to a depth of 5 5 feet below the concrete slab along its northern edge Analytical results identified no detectable concentrations of TPH-D, TPH as jet fuel, or BTEX from samples HB-1 and HB-2 Analytical results from sample HB-3 identified I 1 mg/kg TPH-D 14 mg/kg TPH as het fuel and no detectable concentrations of BTEX above laboratory detection limits ' 2.3 Golden West Environmental Investigation ' In April 1992, Golden West Environmental supervised the drilling and sampling of three soil bonngs (P1, P2, and P3) at the Site Borings PI and P3 were drilled to depths of 25 and 40 feet bgs, respectively Boring P2, an angled boring, was drilled to a calculated depth of 40 feet 1 A total of 21 soil samples were collected and analyzed from the three borings Analytical results identified trace concentrations of TPH-G, TPH-D, TPH as jet fuel (<0 I mg/kg), and BTEX (<0 I mg/kg) in soil samples from borings P 1 and P3 Elevated concentrations of TPH-D (up to 3,100 mg/kg), TPH-G (up to 5,800 mg/kg), TPH asset fuel (up to 3,500 mg/kg), and BTEX (up to 280 mg/kg) were detected in the soil samples from boring P2 The highest concentrations of contaminants in boring P2 were identified in the soil samples collected between 20 feet bgs and 40 feet bgs The vertical extent of contamination detected in soil samples from boring P2 was not fully defined Groundwater was not encountered during this phase of the investigation 2.4 Wallace-Kahl & Associates, Inc. Investigation In February 1993, Wallace-Kuhl & Associates, Inc drilled eight soil borings (MWI through MW3, and BI through B5) Borings BI through B5 were drilled around the perimeter of the former UST excavation to depths between 45 and 50 feet bgs, and borings MW I through ' MW3 were drilled to depths of 60 feet bgs and were constructed as four-inch diameter groundwater monitoring wells In addition to these borings, three hand augered samples (DI-1, DI-2, and DI-3) were collected at a depth of five feet bgs beneath the former fuel dispensers ' A total of 60 soil boring samples and three groundwater samples were collected from the borings and wells The samples were analyzed for TPH as JP4 het fuel (TPH-JP4), TPH-G, TPH-D, and TPH-motor oil using modified EPA Method 8015, and BTEX using EPA Method 8020 Analytical results identified no detectable concentrations of TPH-G, TPH-D, TPH-motor oil or benzene above Iaboratory detection limits in the soil samples TPH as het fuel was identified in the 15, 20, 25, and 30 foot bgs samples from bonng B3 Concentrations of aromatic hydrocarbons in these samples ranged from 3 mg/kg of ethylbenzene in the five-foot sample 4