Laserfiche WebLink
Mr. Gabriel Karr - P.E. Project 939-01.09 <br /> November 1, 16- <br /> Page 3 <br /> ground surface. Six-inch-diameter locking steel casings were installed in <br /> concrete at the surface to house and protect the gas probes. The steel <br /> casings were painted orange so they would be visible to site operating <br /> personnel. <br /> GAS PROBE MONITORING PROCEDURES <br /> Each gas probe was monitored for soil-gas pressure, methane, and oxy- <br /> gen concentrations on October 11 and October 18. The results are pre- <br /> sented in table 2. Oxygen concentrations and combustible gas concentra- <br /> tions (as methane equivalent) were measured with a portable combustible <br /> gas analyzer, the GasTech® Model 1939-OX (GasTech). The GasTech <br /> has a self-contained motorized pump that allow continuous sampling and <br /> analysis of the gas. Soil-gas pressures were measured with a digital <br /> pressure meter, Air-NeotronicsO Model PDM 205. The gas probes were <br /> generally monitored in the early afternoon. <br /> FIELD QUALITY CONTROL <br /> Before field sampling, the GasTech was calibrated in the field. The <br /> GasTech was leak checked, the methane percent and oxygen scales were <br /> calibrated against a certified gas sample containing 49.5 percent methane <br /> and zero (0) percent oxygen. The lower explosive limit (LEL) scale was <br /> calibrated against a certified 20 percent LEL methane standard. These <br /> equipment checks and calibrations are documented in attachment B. <br /> GAS PROBE MONITORING RESULTS <br /> The gas probe monitoring data for the first two monitoring events are pre- <br /> sented in table 2. The maximum of the two methane measurements for <br /> each gas probe casing is presented in the last column. The measured <br /> methane concentrations from all the probes range from undetectable to <br /> 60 percent methane. Methane measurements exceeded the LEL concen- <br /> tration for methane at all gas well locations except GW-6, GW-7, and <br /> GW-9. Higher methane concentrations were typically noted in the inter- <br /> mediate and deeper probe casings, indicating that atmospheric dilution of <br /> the landfill gas is probably occurring at shallow depths in the site soils. No <br /> quantifiable concentrations of methane were measured in any of the probe <br /> casings in GW-6 and GW-7. <br /> PJ9 9390109.GOW <br />