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System (GPS) located on a site figure. Three (3) locations were observed during this monitoring event. If locations are observed to exceed the 200-ppmv reporting threshold during future events, they will be shown in the figure in Attachment 2. To help prevent potential future exceedances, SCS recommends that the landfill surface be routinely inspected and any observed surface erosion be routinely repaired. BACKGROUND The Foothill Landfill is an active organic refuse disposal site. By way of background, organic materials buried in a landfill decompose anaerobically (in the absence of oxygen) producing a combustible gas, which contains approximately 50 to 60 percent methane, 40 to 50 percent carbon dioxide, and trace amounts of various other gases, some of which are odorous. The Foothill property contains a system to control the combustible gases generated in the landfill. SURFACE EMISSIONS MONITORING On November 3 and 4, 2025,the instantaneous and integrated SEM was performed over the surface of the subject site. The monitoring is intended to identify any specific locations or areas of the landfill surface with organic compound concentrations exceeding the LMR threshold limit values of 500 ppmv measured as methane for instantaneous monitoring, or an average methane concentration of 25 ppmv for the integrated monitoring in the 50,000 square foot grids as required under the LMR. During this event, SCS performed the monitoring on a 25-foot pathway following the rules as required. EMISSIONS TESTING INSTRUMENTATION/CALIBRATION The instruments used to perform the landfill surface emission testing consisted of the following: • Thermo Scientific TVA 2020 portable Flame Ionization Detector(FID). This instrument measures methane in air over a range of 1 to 50,000 ppmv. The TVA 2020 meets the State of California Air Resources Board (CARB) requirements for combined instantaneous and integrated monitoring and was calibrated in accordance with the United States Environmental Protection Agency(US EPA) Method 21. • Electronic Weather Anemometer with continuous recorder for meteorological conditions in accordance with the LMR. Instrument calibration logs and weather information are shown in Attachments 5 and 6. SURFACE EMISSIONS MONITORING PROCEDURES Surface emissions monitoring was conducted in accordance with the LMR. Monitoring was performed with the TVA-2020 inlet held within 3 inches of the landfill surface while a technician walked a grid in parallel paths not more than 25 or 100 feet apart over the surface of the landfill. Cracks, holes, and other cover penetrations in the surface were also tested. Surface emissions readings were monitored continuously and recorded every 5 seconds. Any areas in exceedance of the 200 or 500 ppmv standards (reporting and compliance levels, respectively) would be GPS-tagged and stake-marked for on-site personnel to perform remediation or repairs. The integrated average is based on the readings stored on the instrument which are recorded every 5 seconds. The readings are then downloaded and the averages are calculated for each grid using SCS Foothill Landfill—Fourth Quarter 2025 www.scsenaineers.com 2