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North County Landfill Landfill Methane Rule (LMR) Surface Emissions Monitoring Fourth Quarter 2025 INTRODUCTION This letter provides the results of the November 11, 21 and December 1, and 11, 2025, LMR and NSPS surface emissions monitoring(SEM) performed by SCS Field Services (SCS) at the subject site. All work was performed in accordance with our approved contract dated, November 2018, and LMR requirements. SUMMARY AND CONCLUSIONS On November 11, 2025, instantaneous surface emissions testing showed ten (10) exceedances of the LMR instantaneous threshold limit of 500 parts per million by volume (ppmv)for instantaneous monitoring. Based on these monitoring results, corrective actions were taken, and follow-up monitoring was conducted as required. These results are discussed in a subsequent section of this report. In addition, during the instantaneous monitoring event, SCS performed simultaneous integrated monitoring of the landfill surface. During the monitoring events, eight(8) grid areas were observed to exceed the 25-ppmv limit for integrated monitoring. Based on these monitoring results, corrective actions were taken, and follow-up monitoring was conducted as required. These results are discussed in a subsequent section of this report. SCS performed integrated monitoring of the landfill surface as required by the LMR, the landfill was divided into 50,000 square foot areas. The North County Landfill surface area was therefore divided into 84 grids, as shown in Figure 1-A in Attachment 1. In addition, quarterly monitoring of the pressurized piping or components of the Gas Collection and Control System (GCCS)that are under positive pressure must be performed quarterly. Results of the testing of the landfill gas (LFG) Blower Flare Station (BFS) pressurized pipe and components indicated that all test locations were in compliance with the 500 ppmv requirements. Further, as required under the LMR, any location on the landfill that has an observed instantaneous methane concentration above 200 ppmv must be stake-marked and Global Positioning System (GPS) located on a site figure. One (1) location was observed during this monitoring event. When locations are observed to exceed the 200 ppmv threshold, they are shown in the figure in Attachment 3. As stipulated in the LMR, upon completion of four consecutive SEM events without an exceedance of the 25 ppmv or 500 ppmv standards, other than non-repeatable momentary readings, the landfill may request an exemption from the more stringent monitoring required by the rule and apply for a 100-foot spacing requirement on an annual basis for closed landfills or quarterly for active disposal North County Landfill—Fourth Quarter 2025 www.scsenaineers.com 1