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Quarterly Monitoring Report – Third Quarter 2025 <br />www.arcadis.com <br />Forward Landfill 3Q25 Quarterly Mon Report 9 <br />The next annual testing of the LCRS at the Site will be conducted during fourth quarter 2025. <br />4.1.3 Leachate and Surface Impoundment Monitoring <br />Leachate from the sumps at the Site are pumped to surface impoundment WMU-F (F-North) and WMU-F (F- <br />West) for evaporation. The locations of the surface impoundments are shown on Figure 4. <br />During third quarter 2025, leachate was observed in WMU D-88, WMU D-89, WMU D-93/94, WMU D-01, WMU <br />D-02, WMU FU-03, WMU FU-04, WMU FU-05, WMU FU-06, WMU FU-19, WMU FU-23, WMU FU-24, and <br />surface impoundments F-North and F-West. D-89 was unable to be sampled due to riser extension activities <br />being conducted at this location. Sampling details are discussed in Section 4.1.1 and results are presented in <br />Table 8. <br />The volume of leachate pumped to each surface impoundment during third quarter 2025 is documented in <br />Appendix E and summarized in Table 4-1 below (as required by MRP Table 26 [RWQCB 2024]). The freeboard in <br />the surface impoundments was measured weekly; the freeboard logs are also included in Appendix E. The <br />minimum freeboard observed in third quarter 2025 was 7.4 feet in F-North and 7.8 feet in F-West. <br />Table 4-1 Volume of Leachate During Third Quarter 2025 <br />Surface Impoundment <br />Quarterly Pumped <br />Leachate Volume <br />(gallons) <br />Maximum Average <br />Leakage Rate per MRP <br />(gallons/day) <br />Average Pumped <br />Leachate Volume <br />(gallons/day) <br />WMU-F (F-North) 93,600 <br />14,445 <br />1,040.00 <br />WMU-F (F-West) 81,300¹ 903.33 <br />Note: <br />1The flow meter at leachate sump FU-04E was observed as not operating correctly on August 23, 2025. A new flow meter was <br />installed at this location on September 17, 2025. <br />Leachate may be recirculated at the Site in accordance with the RWQCB-approved Leachate Recirculation Plan <br />(Forward 2017). According to the Forward Landfill Operations Manager, leachate recirculation was performed at <br />the Site during third quarter 2025 for dust suppression activities. The Site’s maximum average leakage rate, <br />which was proposed and documented in the 2024 WDRs (RWQCB 2024), is 14,445 gallons per day. The <br />maximum average leakage rate was not exceeded at the Site in third quarter 2025. <br />The Site has approved the disposal of up to 200,000 gallons per year of landfill gas condensate from the Foothill <br />Landfill located in San Joaquin County. During third quarter 2025, the Site did not accept any leachate from the <br />Foothill Landfill. <br />4.2 Leachate Seep Monitoring <br />Leachate seep monitoring is conducted in accordance with MRP Section D.2 (MRP Tables 29 and 30 [RWQCB <br />2024]). The surface seeps at the Site are inspected weekly. <br />No surface seeps were observed at the Site during third quarter 2025; therefore, no seep samples were collected.