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FORWARD/AUSTIN LANDFILL <br /> PERIMETER LANDFILL GAS (LFG) MONITORING PROBE <br /> AND ON-SITE STRUCTURE TESTING <br /> FIRST QUARTER 2023 <br /> INTRODUCTION <br /> This letter provides results of gas monitoring probes (GMP) and on-site structure testing for the first <br /> quarter of 2023 (January through March) performed by SCS Field Services (SCS). All testing, <br /> monitoring protocols and reporting were performed in general conformance with Title 27 California <br /> Code of Regulations (CCR)Article 6. Briefly, these regulations require that solid waste disposal site <br /> owners/operators implement LFG control or monitoring provisions to ensure that methane gas <br /> concentrations in soils at the property boundary do not exceed the lower explosive limit(LEL, or 5 <br /> percent by volume) and that interiors of on-site structures do not exceed 1.25 percent by volume in <br /> air. Below is a summary of our quarterly monitoring activities. <br /> SUMMARY AND CONCLUSIONS <br /> On January 31, March 20, 28 and 29, 2023, no methane gas (the combustible component of LFG) in <br /> excess of the LEL(5 percent by volume) was detected at any perimeter subsurface compliance GP <br /> probe location tested or in excess of 1.25 percent by volume in air at any interior locations or on-site <br /> structures. These results indicate that at the time of our testing the subject site perimeter <br /> subsurface GP probes and interiors of on-site structures are in compliance with requirements of Title <br /> 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—First Quarter 2023 www.scsengineers.com <br /> 1 <br />