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r - <br /> I <br /> Harding Lawson Asuoalotos <br /> I INTRODUCTION <br /> This report documents the initial investigation of <br /> 9 the gasoline leak by <br /> Harding Lawson Associates (HLA) at the 7-Eleven facility located at 455 West <br /> Grant Line Road in Tracy, California. The facility has three underground <br /> gasoline tanks, one of which has leaked and has now been emptied (see Plate 1). <br /> The leaking gasoline tank was identified to contain unleaded fuel and to have <br /> a capacity of 10,000 gallons. The purpose of our study was to evaluate the <br /> r �¢ <br /> lateral extent of gasoline constituents in soil and water by installing four <br /> on-site ground-water monitoring wells. <br /> i; Our scope of services was as follows: <br /> I. Bail two existing wells on site, noting the presence of free product <br /> 2. Drill borings near each corner of the site and install ground-water <br /> monitoring wells <br /> f � � <br /> 3. Screen all soil samples in the field using a portable gas indicator* <br /> 4. Develop the .four ground-water monitoring wells and obtain ground-water <br /> t samples <br /> { 5. Perform chemical tests on selected soil samples from each boring and <br /> on water samples from each of the wells <br /> i <br /> 6. Survey well locations <br /> ` in order to calculate the local gr <br /> gradient ound-water <br /> 7. Perform laboratory tests to determine if the underlying soils are cc <br /> rosive <br /> Wi <br /> 8. Review existing records and determine t <br /> wells he presence and usage of nearby'tg i <br /> r r . 21. <br /> j <br /> ! - - - - - - <br /> * A Johnson Gas Indicator AfP-204 calibrated to hexane, was used to measure the <br /> presence .of'vaporized hydrocarbons. <br />