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Environmental Consultants 4707 Greenleaf Circle 209 545-8490 <br /> suite F Fax 209 545-8391 <br /> Modesto, CA 95356 www.scsengineers,com <br /> July 19, 2006 <br /> File No, 07202055.00 <br /> Ms. Christina Carbajal <br /> Forward Landfill <br /> 9999 S. Austin Road <br /> Manteca, Calif mua 95336 <br /> Subject; Operation,Monitoring, and.Maintenance of the Landfill Gas(LFG) Migration <br /> Control Facilities at the Forward/Austin Landfill,Manteca., California <br /> Dear Ms. Carbajal, <br /> This letter provides a status report on the operation;,monitoring, and maintenance (O&M)work <br /> performed by SCS Field Services(SCS)on the subject system. All activities were performed in <br /> accordance with our approved contract work scope dated February 14, 2003. Below is a summary <br /> of O&M efforts during the period of June 1 through 30,2006. <br /> Conclusions and B�ecorqmendations <br /> As of the dates of our testing,the LFG control facilities appeared to be operating ti act and <br /> generally meeting the operational. criteria. Also,no methane gas concentrations above the LEL <br /> were detected at only Perimeter Monitoring Probe tested. ,Also, on June 14, 2006, SCS performed <br /> monitoring of Temporary Gas Probes, defined as TGP-01 through TGP-39,as directed by the <br /> Client. Results of this monitoring indicated that methane gas concentrations in excess of the LEL <br /> were detected at several locations tested,(up to 58.4 percent by volume). Note,that these probes <br /> are irAended for evaluation purposes only and are not compliance locations. ,All LFG extraction <br /> wells were observed to be.receiving adequate vacuum and several were adjusted during this <br /> monitoring panod. Recommendations regarding repair or maintenance activities may be <br /> contained in subsequent sections of this report. Please advise SCS as soon as possible <br /> regarding implementation of these recommendations. <br /> BackgKound <br /> As you know,the ForwardlAustia 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,40 <br /> to 50 percent carbon dioxide,and trace amounts of various other gases, some of which are <br /> odorous. The Forward/Austin property contains a system to control the combustible gases <br /> 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 likelihoodthat the LFG will mi grate to <br /> off-site locations. <br /> OfFices Natianwicle <br />