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Quarterly Monitoring Report – Third Quarter 2025 <br />www.arcadis.com <br />Forward Landfill 3Q25 Quarterly Mon Report 8 <br />4 Additional Facility Monitoring <br />This section describes additional facility monitoring of leachate, seeps, cannery waste land application, and the <br />Site. Additional facility monitoring is conducted in accordance with MRP Section D (RWQCB 2024). <br />4.1 Leachate Monitoring and Leachate Collection and <br />Removal System Testing <br />This section describes leachate monitoring activities and testing of the leachate collection and removal system <br />(LCRS) during third quarter 2025, along with the associated monitoring results. The LCRS testing is conducted in <br />accordance with MRP Section D.1 (MRP Tables 25 through 28 [RWQCB 2024]). <br />4.1.1 Leachate Monitoring <br />Leachate samples are collected quarterly at the Site. The LCRS sump monitoring network in MRP Table 25 <br />includes 22 locations (RWQCB 2024). Of note, locations TS-1 (FU-23) and TS-2 (FU-23) replaced MRP location <br />FU-23, and locations TS-3 (FU-24) and TS-4 (FU-24) were not included in the MRP. These locations (TS-1 <br />through TS-4) were added in fourth quarter 2024. As a result, the LCRS sump monitoring network should have a <br />total of 25 locations, as presented in Table 1 and Figure 4. Additionally, sump D-93/94 for waste management unit <br />(WMU) D-93/94, listed in Table 25 of the MRP, was improperly labeled in the field as D-93/95 and has been <br />labeled as D-93/95 since May 13, 2020 (see location on Figure 4). The appropriate nomenclature has been used <br />since second quarter 2025. <br />Quarterly leachate monitoring includes the field analyses and laboratory analyses specified in MRP Table 27 <br />(RWQCB 2024). Leachate monitoring was conducted on August 7 and August 15, 2025. Leachate samples from <br />the LCRS sump monitoring network at the Site are also analyzed semiannually for dissolved inorganic <br />constituents and metals, as required by Water Code Section 13267 Order for Technical Reports Regarding <br />Acceptance of Hazardous Waste, Forward Landfill, San Joaquin County (RWQCB 2017b; see Section 3.1). The <br />semiannual laboratory analyses are scheduled for the first and third quarters of the calendar year. The field and <br />laboratory monitoring results for third quarter 2025 are summarized in Table 8. <br />4.1.2 Leachate Collection and Removal System Testing <br />The LCRS at the Site is tested annually in accordance with MRP Section D.1.a (RWQCB 2024). In addition, an <br />annual inspection of each sump is performed by Del-Tech, which most recently occurred on November 8 and 9, <br />2024. Visual inspections of sumps are also performed weekly by Del-Tech. Documentation of this process is <br />included in Appendix E. <br />LCRS continuity testing consists of injecting a high-concentration tracer dye into the far side of the LCRS and <br />allowing the liquids to migrate through the unit to settle in the low point of the LCRS sump. The non-toxic tracer <br />dye liquids allow migration to the lowest point of the sump. Once the tracer dye has migrated through the system, <br />it can be extracted and detected from the sump extraction pipe, indicating that a conduit is present through the <br />unit. If excessive liquid is backed up into the drainage layer of the LCRS, the tracer dye will take longer to migrate <br />to the sump.