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' Options to consider in the design of a perimeter LFG control system are the well vacuum and the well spacing. An increase in the well vacuum may extend the ROI of the extraction wells sufficiently to form the "vacuum curtain", as was the intent of the initial design. ' However, the option of reducing the well spacing was selected as the more conservative approach. 3.0 SYSTEM OPERATION 1 3.1 INTRODUCTION ' Waste decomposition and the production of LFG can be a very lengthy process and depends on a variety of factors including the amount, type, and moisture content of the ' waste. In many instances, LFG extraction systems have to operate for a substantial number of years after waste is placed to keep sites in compliance with today's regulations. However, given the fact that Forward Landfill has an active interior gas extraction system ' and that additional wells are scheduled to be installed around WMU-B and WMU-C, migration to the western perimeter is expected to diminish. The perimeter system described herein is intended to serve as a temporary measure to bring the site into ' compliance. 3.2 INITIAL SYSTEM OPERATION The perimeter gas migration control system will operate as a "vacuum curtain" until levels at the property boundary are within regulatory guidelines. Each year the perimeter system will be evaluated to determine if the system can be reduced or eliminated from operation and monitoring. Probes GP -8 and GP -9 will continue to serve as the primary regulatory compliance points for the southwestern boundary of the site once the perimeter system is ' removed from service. If deemed appropriate to scale back the operation and monitoring of the temporary system, Forward will provide documentation that justifies this course of action. The temporary wells and probes installed will be left intact in case it is warranted that the system be brought back on-line. ' 4.0 SCOPE OF WORK ' 4.1 CONSTRUCTION ACTIVITIES BAS recommends the installation of thirty-nine (39) additional LFG probes be installed along ' the western property boundary. The probes will be installed in between existing and proposed gas extraction wells, with spacing not to exceed 40 feet. Thirteen (13) LFG ' extraction wells will be installed at a maximum of 40 feet spacing during the initial installation. This spacing is based on the results of the simulation which provides 1 9 Installation Work Plan to Remediate Landfill Gas Migration ):\Allied\Forward\Workplan\Forward Evaluation - rev4.doc:9/15/2004