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APPROACH <br /> The EMP applied a"step-out, step-down" approach based on the assumption that, although <br /> contamination was no longer found at MW-3, groundwater beyond MW-3 could be <br /> contaminated. This approach included drilling temporary exploratory borings TB-1 and TB-2 <br /> approximately 500 feet down-gradient from MW-3, located to maximize the potential to detect <br /> groundwater impact. <br /> If contamination was confirmed at either TB-1 or TB-2, then supplementary temporary borings <br /> i 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, deeper sample. This is <br /> the "step-down" component of the EMP,to assess the vertical extent 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, a sample of soil gas was <br /> collected from deep beneath the surface, near the groundwater table. A sample of landfill gas <br /> (LFG)was also collected from the refuse adjacent to MW-3 for comparison with the soil gas <br /> collected near W-3 and for comparison with groundwater. <br /> PROCEDURE <br /> The work proceeded in accordance with the EMP. <br /> Exploration <br /> Temporary exploratory borings TB-1 and TB-2 were drilled using a Versa-Drill V-1000X <br /> drilling rig utilizing air rotary drilling methods. Cuttings were sampled every 5 feet to identify <br /> and log the soils encountered. Ted Sison, Staff Scientist with SCS Engineers,inspected and <br /> recorded all drilling activities and logged encountered soils (Appendix B). The work was done <br /> ifrom June 12 to 20, 2003. <br /> Analyses <br /> Groundwater samples were sampled and analyzed for VOCs in accordance with the approved <br /> ' Sampling and Analysis Plan, and EPA Method 8260B. <br /> Soil gas samples were analyzed for VOCs using EPA Method TO-14A. <br /> Engineering Feasibility Report 2 Foothill Sanitary Landfill <br /> October 1,2003 San Joaquin County Solid Waste <br />