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yy 4 1 <br /> Ll ' <br /> r <br /> Mr Paul Supple Project 20805-140 003 <br /> April 30, 1998 <br /> Page 2 <br /> • Resurfacing of the former UST complex and piping trenches and waste oil UST <br /> location <br /> • Removal of stockpiled soil on April 10, 1998 <br /> BACKGROUND <br /> UST Complex <br /> The gasoline UST complex consisted of two 4,000-gallon and one 6,000-gallon <br /> single-wall fiberglass-coated steel tanks and one 10,000-gallon single-wall fiberglass tank <br /> The 10,000-gallon UST formerly stored leaded gasoline The gasoline UST fill ports <br /> were located at the northern ends of the tanks Fiberglass piping located at the northern <br /> ends of the USTs connected the USTs to two dispenser islands located north of the <br /> station building One 280-gallon waste-oil tank was located west of the gasoline UST <br /> complex (see Figure 2) <br /> Previous investigations <br /> From December 1990 through November 1993, RESNA Industries, Inc (RESNA <br /> [formerly Applied GeoSystems]), of Rancho Cordova, California, observed the drilling of <br /> 21 borings (B-1 through B-21) and the installation of 5 on-site groundwater monitoring <br /> wells (MW-1 through MW-5), 1 off-site groundwater monitoring well (MW-6), and <br /> 4 vapor extraction wells (VW-1 through VW-4) (RESNA, June 26, 1992, Report <br /> No 30004-4, RESNA, June 21, 1993, Report No 30004-8, and RESNA, May 11, 1994, <br /> Report No 30004-8). The locations of soil borings, wells, and other site features are <br /> presented on Figure 2 Residual hydrocarbons were analytically identified m soil samples <br /> collected from the borings near the tank cavity Low concentrations of hydrocarbons <br /> were detected in soil samples collected from the borings near the dispenser islands <br /> During drilling of soil boring B-18, a product line was accidentally fractured and product <br /> leaked into the adjacent soil RESNA collected a soil sample from 6 feet below the <br /> product line (S-6-PL1), gasoline hydrocarbons were detected in this sample RESNA <br /> installed one vapor extraction well (VW-4) near the product release Total petroleum <br /> hydrocarbons as gasoline (TPHG) and benzene, toluene, ethylbenzene, and total xylenes <br /> (BTEX) were below laboratory detection limits in soil collected at 11 feet, 26 feet, and <br /> 46 feet below ground surface (bgs) <br /> SAC\N\PJM805\(}8051400 3FS-981pzusmer L <br />