COMPLIANCE INFO_1968-2006 - Laserfiche WebLink

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However , as settlement continued , the subsurface fire regen- erated, resulting in a void beneath a portion of the concession - building . Cracks and fissures in the void surface resulting from the combustion of materials provided a natural draft pathway for air into the landfill , and allowed smoke to vent freely to the subfloor area . The void was filled and sealed by injecting a bentonite clay/sand slurry beneath the building. To extinguish the subsur- face fire, eight injection wells were located to a depth of 30 to 35 ft within the vicinity of the fire. The wells were used to determine the limits of the fire , to monitor subsurface temper- ature and gas composition, and to provide a conduit for carbon dioxide (CO2) injection . To extinguish the subsurface fire , approximately 25 tons of liquid CO2, at -109°F and 300 pounds per square inch (psi ) , was injected into the eight wells to cool subsurface temperatures and to displace any oxygen present. Monitoring for subsurface tem- peratures and carbon monoxide indicates that the fire has been successfully controlled. SUMMARY Development of a completed landfill site must account for the significant problems associated with settlement and gas pro- duction . These problems become significantly greater when occu- pied structures are included as part of the development . Devel - opment can be accomplished with the design and installation of a properly engineered LFG control system, and routine maintenance of the system. The decision to develop a landfill site with the necessary protection system requires effective operation , mainte- nance , and monitoring programs carried out by qualified personnel to ensure that the LFG control systems provide continuous, safe conditions for site occupancy. LFG-75