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' k <br /> 29 august 19 88 <br /> Laurie Cotulla k <br /> San Joaquin L Health District <br /> 7-11 IK TRACY, 525 BEST GRANT LINE ROAD . <br /> Harding Lawson Associates (HLA) submitted a work'plan to drill a 60 foot well <br /> on the 7-l 1 property to determine the vertical extent of 1 gasoline <br /> contamination. Considering that first ground water is about five feet, it <br /> appears that 60 feet is excessive. HLA presumes that there is a confining layer <br /> that separates first and second water. While this may bi� true, it would be <br /> better to drill into (not through) the confining layer to determine whether the <br /> gasoline has even reached the layer. If it has, a deep well may be in order. <br /> However, that should be determined at that time. <br /> We agree that other wells are needed; especially in the area between MW- 2 <br /> and ISI - 12 which could help determine whether the subsurface fill beneath <br /> the 7-11 convenience store (probably gravel) has acted-as a conduit for <br /> gasoline. This would help explain the concentrations found in MSI- 14, which <br /> FILA says "...a pear to be anomalous...... HLA should:resam le and analyze the <br /> ground water by GCFID for TFH and method 8020 for BT%&E. <br /> The report shows high levels of dissolved and gaseous phase gasoline near and <br /> projected under the convenience store. Have any vapor,-studies been <br /> conducted inside the building? With ground water so shallow and porous <br /> material beneath a building, our.experience has shown that vapors can enter <br /> buildings via the sewer and other pipelines. <br /> fi <br /> If you have any questions, please call me at (916) 36 1-040. <br /> Gordon Lee Boggs <br /> Underground ank <br /> Program Coordinator F <br /> 4 <br /> . F <br />