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Mr. Tom Morton May 7, 1987 Page 2 CONCLUSIONS AND RECOMMENDATIONS The results indicate that LFG has moved through the subsurface soils away from the refuse-filled areas near Probes 1, 2, 4, 9, and 10 at concentrations greater than 5 percent (the lower explosive limit for methane in air) . Lesser migration of LFG is presently occurring near Probes 3, 6, 7, and 8 and none was detected at Probe 5. The actual extent of LFG migration has not been determined but it is likely to extend into the nearby farm labor housing facility, particularly in the first row of buildings on the east side. Although the design of the structures within the housing facility included some gas control measures, i.e. , underfloor gravel and vent pipes with risers, it is recommended that the following actions be taken: • Investigate for the presence of combustible gas within the soil at close proximity to the structures. This can be accomplished by driving bar holes 2 to 3 feet into the soil and sampling beneath the ground surface with a combustible gas detector. (The gas control system's vent risers might also give an indication of the presence of gas beneath the buildings.) • If combustible gas is found in the soil or in the risers, then the interior of the structure should be monitored for the possible presence of combustible gas. If combustible gas is found, the point(s) of gas entry must be found and sealed immediately. • Regardless of whether LFG is found nearby, the interior of the buildings should be inspected periodically to check the integrity of the concrete floor and to observe floor cracks, joints, and utility penetrations for proper seal- ing. • Installation of additional gas monitoring probes should be considered between the buildings and the refuse fill to permit more accurate measurement of the LFG movement.