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t t <br /> Environmental Consultants 4707 Greenleaf Circle 209 545-8490 <br /> Suite F Fax 209 545-8391 <br /> Modesto, CA 95356 www.scsengineers.com <br /> June 22, 2006 <br /> File No. 07202055.00 <br /> Ms. Christina Carbajal <br /> Forward Landfill <br /> 9999 S. Austin Road <br /> Manteca, California 95336 <br /> Subject: Second Quarter 2006 San Joaquin Valley Unified Air Pollution Control District <br /> (SJVUAPCD) Rule 4642 Surface Emissions Testing at the Forward Landfill, <br /> Manteca, California <br /> Dear Ms. Carbajal: <br /> This letter provides results of the April 26, 2006, SJVUAPCD Rule 4642 landfill surface <br /> emissions/component monitoring performed by SCS Field Services (SCS) at the subject site. All <br /> work was performed in accordance with our current contract. <br /> Summary and Conclusions <br /> On April 26, 2006, surface and/or component emissions testing showed no exceedences of the <br /> SJVUAPCD Rule 4642 threshold limit of 500 ppmv. The highest surface and/or component <br /> reading detected was 50 ppmv. Based on these test results, no additional testing is required at <br /> this time. Therefore, the next quarterly surface test event is due by the end of September 2006. <br /> Background <br /> As you know, the Forward Landfill site is an active organic refuse disposal site. By way of <br /> background, organic materials buried in a landfill decompose anaerobically (in the absence of <br /> oxygen) producing a combustible gas which contains approximately 50 to 60 percent methane <br /> gas, 40 to 50 percent carbon dioxide, and trace amount of various other gases, some of which are <br /> odorous. The Forward Landfill property contains a LFG collection and flare system to control <br /> the combustible gases generated in the landfill. <br /> The gases produced in a landfill will either vent vertically to the atmosphere or migrate <br /> horizontally through subsurface soil to locations on adjacent properties. If the soil surrounding a <br /> landfill consists of permeable materials, there is a greater likelihood that the LFG will migrate to <br /> off-site locations. If the methane gas component of LFG is allowed to accumulate in a confined <br /> area (i.e., utility lines, irrigation valve boxes, vaults, basements, wall spaces, etc.) and is exposed <br /> to an ignition source, it can be explosive at concentrations between 5 and 15 percent by volume. <br /> At higher concentrations, methane is flammable. However, the presence of methane gas in site <br /> soil does not mean there is an immediate threat of explosion because flames cannot typically <br /> propagate through soil. <br /> Offices Nationwide <br />