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4.4 SAMPLING AND ANALYSIS PROCEDURES <br /> The gas probes were sampled February 16 and 18, 1988, no earlier than <br /> 24 hours after they had been installed. Before the sample was col - <br /> lected, two well volumes were purged from the probe. The probe was <br /> sampled immediately after it was purged. <br /> An OVA and GasTech were then used in the field to measure the sample's <br /> total organics as methane. The OVA is a factory-calibrated instrument <br /> (Section 5.1.1) . The GasTech was calibrated in the office as dis- <br /> cussed in Section 5. 1 .1 . <br /> 4.5 RESULTS <br /> Table 6 lists the total organics measured as methane and the sampling <br /> information for each probe. In Probes P-2, P-3, and P-4, located on <br /> the southern perimeter of the landfill , methane concentrations were <br /> detected in the range of 0.0002 to 0.001 percent by volume (2 to <br /> 10 ppm) . In Probe P-5, 0.4 percent by volume total organics measured <br /> as methane was detected. Probes P-1 and P-6, located near the en- <br /> trance of the landfill , contained the highest levels at 50 and 30 per- <br /> cent by volume, respectively, indicating possible off-site gas migra- <br /> tion at the northwestern boundary of the landfill . <br /> PJ9 9390304.00D 4-2 Rev. 0 09/20/88 <br />