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Quarterly Monitoring Report – Third Quarter 2025 <br />www.arcadis.com <br />Forward Landfill 3Q25 Quarterly Mon Report 5 <br />Pan lysimeters FU-19E and FU-19W are not listed in the MRP and were not monitored until second quarter 2025. <br />Sumps FU-19E and FU-19W are listed (MRP Table 25 [RWQCB 2024]), as shown on Figure 4. When pan <br />lysimeters FU-19E and FU-19W were visited for sampling in third quarter 2025, the locations were dry. The <br />locations should be included in Table 6 of the MRP in the next revision. <br />The lysimeter samples were analyzed in accordance with MRP Tables 8 and 9 (RWQCB 2024). Tables 5a and 5c <br />detail results of soil pore liquids if they are present during the monitoring event. Supplemental analyses are <br />conducted every 5 years. The next 5-year analyses will be conducted in third quarter 2028 (MRP Table 10 <br />[RWQCB 2024]). <br />The MRP also states that each lysimeter will be screened for methane or VOCs by a gas analyzing device or <br />photo ionization detector, and a USEPA Method TO-15 VOC sample may be obtained (MRP Section B.2.b and <br />Table 7 [RWQCB 2024]). This process began in second quarter 2025. The prescreening of methane was <br />conducted using a gas analyzing device for methane detection. A USEPA Method TO-15 VOC sample should <br />only be collected if the methane concentration exceeds 1% by volume. The screening results are included in <br />Table 5a. During the prescreening activities, one suction lysimeter (FU-05-B) had a concentration of 14.0% <br />methane. Suction lysimeter FU-05-B was then sampled for VOCs by USEPA Method TO-15 and the results are <br />presented in Table 5b. <br />2.2.2 Quarterly Results <br />Field inspection results are provided in Appendix B. All but three of the lysimeters were dry or contained <br />insufficient soil pore liquids for sampling. Three suction lysimeters (LY-A, LY-Pond-N, and FU-04W-B) at the Site <br />contained sufficient liquid for analysis of VOCs. A fourth suction lysimeter (LY-Pond-S) was damaged and unable <br />to be sampled. <br />Tables 5a and 5c present analytical results for suction and pan lysimeter locations, respectively. As shown in the <br />tables, VOCs were detected at concentrations exceeding the applicable MDLs or PQLs at the Site during third <br />quarter 2025. Cumulative data for all monitoring points for the unsaturated zone for the past year (third quarter <br />2024 through third quarter 2025) are included in Appendix D. <br />2.3 Surface Water Monitoring <br />This section describes surface water monitoring conducted during third quarter 2025 and the associated results. <br />Surface water monitoring is conducted in accordance with MRP Section B.3 (RWQCB 2024). <br />2.3.1 Monitoring Program <br />Two creeks are present near the Site (Figure 1). The north fork of Littlejohn’s Creek borders the north and west <br />sides of the Site. The south fork of Littlejohn’s Creek borders the south side of the landfill area on the east and <br />west sides of the Site. Both creeks are dammed upstream by Farmington Dam and usually are dry. Surface runoff <br />from the landfill areas is channeled to sedimentation basins, which are located near the southwest corner of the <br />Site, adjacent to the creeks, as shown on Figure 5. The water in the sedimentation basins typically is evaporated. <br />Four surface water monitoring points have been established for the Site (MRP Table 11 [RWQCB 2024]). The <br />surface water monitoring locations are described in Table 2-1 below and shown on Figure 5.