CORRESPONDENCE_2000-2002 - Laserfiche WebLink

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BUR Procedures Perimeter landfill gas monitoring was conducted at seven landfill gas probes during May 1, 2002 by LFR personnel. Concentrations of methane, oxygen, and carbon dioxide within the seven soil gas probes were monitored using a calibrated Landtec GEM 2000 gas analyzer and extraction monitor (GEM). The GEM was certified as calibrated to factory specifications by the rental supplier, EquipCo, prior to each sampling event. At each probe, a reading of ambient air in the vicinity of the probe being tested was recorded before soil gas was monitored within the probe. Initially, the GEM was attached to the soil gas probe, the valve was opened, and the initial soil gas probe pressure was monitored and recorded. Then the GEM's internal pump was activated to extract soil gas from the probe. Readings for methane, oxygen, and carbon dioxide were monitored until the readings stabilized. After the readings were recorded, the internal pump was deactivated and the post-reading soil gas probe pressure was monitored and recorded. The soil gas probe valve was then closed, and the GEM was disconnected. The main office, maintenance yard buildings, and the weigh station were also monitored to assess potential gas accumulations at the foundations. The landfill gas probe and building locations are shown on Figure 2. LFR personnel were unable to locate landfill gas probes GP-1, GP-2, or GP-3. These three probes have apparently been buried with soil by earth moving equipment. As a result, no monitoring was conducted at these locations. Results As shown in Table 1, methane was detected above its lower explosive limit (LEL) in GP-10 at Forward Landfill during the second quarter of 2002. The GEM displayed a stable reading of 5.8 percent by volume for methane at GP-10. Methane was not detected at the other Forward Landfill soil gas probes during the second quarter of 2002. Oxygen readings in soil gas probes ranged from 16.7 percent by volume in GP-10 to 21 percent by volume in GP-9. Carbon dioxide readings ranged from 0.0 percent by volume in GP-9 to 3.7 percent by volume in GP-10. These data are generally consistent with previous soil gas data at this site. The relative pressure of the probes ranged from -0.1 to 0.1 inches of water indicating that the pressure within the soil gas probes is at or near equilibrium with atmospheric pressure. Methane was not detected during monitoring of the buildings (office, yard, and scale house) at Forward Landfill.