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Mr. Gabriel Kar c* *Project 939-01.09 <br /> April 9, 1992 <br /> Page 5 <br /> Underground vaults and manholes in the migrant housing facility were also <br /> monitored for combustible gas concentrations. Recent storms had <br /> saturated the ground and flooded many of the vaults, decreasing the <br /> probability of detecting landfill gas in exterior areas. No methane was <br /> detected in any of the underground structures monitored. <br /> From the observations of the monitoring staff and conversations with Mr. <br /> Bob Reed of the Housing Authority, the houses appear to be well-isolated <br /> from potential gas intrusion. Mr. Reed stated that the soil pads below the <br /> units were compacted to 97 percent of maximum Proctor density to <br /> minimize the potential for differential settlement and concrete slab <br /> cracking. Two low permeability synthetic membranes were integrated into <br /> the concrete floor slabs, and a passive gas venting system was included <br /> below the slabs and in the utility trenches. EMCON staff noted no cracks <br /> in the floors, walls, or ceilings of the houses and only very minimal hairline <br /> cracking of exterior concrete pavements, supporting the assertion of <br /> adequate foundation construction. <br /> The landfill site equipment building and office was also monitored for <br /> landfill gas intrusion with the GasTech. No methane was detected in the <br /> site buildings. <br /> CONCLUSIONS <br /> The gas monitoring wells along the western, northern, and northeastern <br /> property lines appear to contain concentrations of methane exceeding the <br /> Title 14 regulatory limit of 5 percent by volume. Measurements in wells <br /> along the southern edge of the site frequently did not detect methane. <br /> Methane gas was not detected in any of the monitored on-site or off-site <br /> structures, which included most of the units in the migrant labor housing <br /> development adjacent to the western boundary of the landfill site. <br /> The analysis of three gas samples for the ten AirSWAT compounds <br /> detected the same compounds as those found in samples analyzed during <br /> the Calderon AirSWAT testing program performed in 1988. The total <br /> concentration of AirSWAT compounds in the current sample set from the <br /> PJ9 9390109.EOW <br />