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FORWARD/AUSTIN LANDFILL <br /> PERIMETER LANDFILL GAS (LFG) MONITORING PROBE <br /> AND ON-SITE STRUCTURE TESTING <br /> FOURTH QUARTER 2022 <br /> INTRODUCTION <br /> This letter provides results of gas monitoring probes (GMP) and on-site structure testing for the <br /> fourth quarter of 2022 (October through December) performed by SCS Field Services (SCS). All <br /> testing, monitoring protocols and reporting were performed in general conformance with Title 27 <br /> California Code of Regulations (CCR)Article 6. Briefly, these regulations require that solid waste <br /> disposal site owners/operators implement LFG control or monitoring provisions to ensure that <br /> methane gas concentrations in soils at the property boundary do not exceed the lower explosive limit <br /> (LEL, or 5 percent by volume) and that interiors of on-site structures do not exceed 1.25 percent by <br /> volume in air. Below is a summary of our quarterly monitoring activities. <br /> SUMMARY AND CONCLUSIONS <br /> On October 6, 7 and 10, 2022, no methane gas (the combustible component of LFG) in excess of the <br /> LEL was detected at any perimeter subsurface compliance GP probe location tested or in excess of <br /> 1.25 percent by volume in air at any interior locations or on-site structures. These results indicate <br /> that at the time of our testing the subject site perimeter subsurface GP probes and interiors of on- <br /> site structures are in compliance with requirements of Title 27 CCR. <br /> GAS TESTING INSTRUMENTATION AND METHODS <br /> Testing for methane gas, oxygen gas, carbon dioxide gas and pressure was performed using a <br /> Landtec GEM-5000 Gas Analyzer calibrated to methane gas. The instrument measures combustible <br /> gas concentrations as a percentage by volume (0 to 100 percent) in the gas sampled. The detection <br /> limit for this instrument is approximately 0.10 percent by volume. <br /> Gas monitoring probe testing procedures are as follows: <br /> • Connect sample tubing, open test valve; observe pressure and record data. <br /> • For probes 20 feet deep or less, turn on sample pump, observe and record methane, <br /> oxygen, and carbon dioxide gas concentrations, when readings have stabilized for 30 <br /> seconds. <br /> • For probes more than 20 feet deep, turn on sample pump, extract a minimum of one <br /> probe volume, observe and record methane, oxygen, and carbon dioxide gas <br /> concentrations, when readings have stabilized for 30 seconds. <br /> • Close test valve, disconnect sample instruments and secure sample location. <br /> Forward/Austin Landfill—Fourth Quarter 2022 www.scsenaineers.com <br /> 1 <br />