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The EMP was submitted due to the indicated presence of a few VOCs at groundwater monitoring <br /> well MW-3 (Figure 1). These detections were reported from March 2000 to October 2001. <br /> MW-3 is one of two down-gradient wells monitoring for impact to groundwater by the Foothill <br /> Landfill. <br /> Other than suspected "false positive" results due to contamination of water samples after <br /> collection,VOCs have not been detected in this well or at any well at the Foothill Landfill since <br /> October 2001. <br /> DELINEATION OF RELEASE <br /> GENERAL <br /> The delineation of the release proceeded in accordance with the approved EMP. <br /> The EMP applied a"step-out, step-down" approach based on the assumption that, although <br /> VOCs were no longer found at MW-3, groundwater beyond MW-3 could be contaminated. This <br /> approach included drilling temporary exploratory borings TB-1 and TB-2 approximately 500 feet <br /> down-gradient from MW-3, located to maximize the potential to detect groundwater impact <br /> (Figure 1). <br /> If contamination was confirmed at either TB-1 or TB-2, then supplementary temporary borings <br /> would be drilled, and the groundwater sampled down-gradient from the boring at which <br /> contamination was confirmed. This is the "step-out" component of the EMP,to assess the lateral <br /> extent of contamination, if any. <br /> Additionally,if contamination was detected at the top of the aquifer at either of these two <br /> temporary borings,the boring would be drilled deeper to take a second sample from deeper <br /> within the aquifer. This is the "step-down" component of the EMP,to assess the vertical extent <br /> I ' of contamination, if any. <br /> Any well at which contamination was confirmed would be converted to a permanent monitoring <br /> well. <br /> Recognizing the possibility that contamination could be detected, and that, if detected,the source <br /> of the contamination could be landfill gas (LFG), a sample of soil gas was collected from deep <br /> beneath the surface,near the groundwater table. A sample of LFG was also collected directly <br /> from the refuse adjacent to MW-3 for comparison with the soil gas collected near MW-3 and for <br /> comparison with constituents found in the groundwater. <br /> Engineering Feasibility Report 2 Foothill Sanitary Landfill <br /> October 30,2003 San Joaquin County Solid Waste <br />