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Revised Quarterly Monitoring Report – <br />Fourth Quarter/Annual 2024 <br />www.arcadis.com <br />Revised - Forward Landfill 4Q24 Quarterly Mon Report 06262025 2 <br /> Eight groundwater monitoring wells were installed after the issuance of the MRP (AMW-54R, AMW-60S, <br />AMW-60M, AMW-61M, AMW-61S, AMW-62, AMW-63, and AMW-64) and were added to the groundwater <br />monitoring network. <br /> Four offsite monitoring wells (7833-MW-01 through 7833-MW-04) are monitored quarterly. <br />For evaluation purposes, the groundwater monitoring wells at the Site have been divided into three groups based <br />on the depth of the screened interval (shallow, intermediate, and deep). Shallow wells are screened <br />predominantly at elevations greater than -50 feet relative to mean sea level (MSL). Intermediate wells are <br />screened predominantly at elevations of -50 to -125 feet relative to MSL. Deep wells are screened predominantly <br />at elevations below -125 feet relative to MSL. <br />During the fourth quarter 2024 groundwater monitoring event, all the locations in the current groundwater <br />monitoring network were sampled with the exception of three locations. Three piezometers (PZ-1, PZ-2, and PZ- <br />3) located offsite on the California Department of Corrections and Rehabilitation (CDCR) Property north of Site <br />will be added to the groundwater monitoring event in second quarter 2025 in accordance with the MRP (RWQCB <br />2024a). <br />Supplemental analyses are conducted every 5 years. The next 5-year analyses will be conducted in third quarter <br />2028 (MRP Table 4 [RWQCB 2024a]). <br />2.1.2 Field Activities <br />Quarterly sampling was conducted in accordance with the Sampling and Analysis Plan, as provided in Appendix <br />A, and the MRP (Section B.1 and Tables 2 and 3;RWQCB 2024a). Well monitoring was conducted by Del-Tech <br />Geotechnical Support Services (Del-Tech), located in Oakdale, California. Del-Tech collected depth-to-water <br />(DTW) measurements at all monitoring wells between November 7 and 22, 2024 and collected groundwater <br />samples between November 13 and December 6, 2024. <br />DTW measurements were collected at each well before purging and sampling, with field records provided in <br />Appendix B. The groundwater elevation data for the Site are summarized in Table 2, and a groundwater elevation <br />contour map is provided as Figure 8. Groundwater in the vicinity of the site generally flowed towards the <br />northeast, with an average hydraulic gradient of approximately 0.002 foot per foot and an average flow rate of <br />approximately 2.0 feet per day (730 feet per year) (MRP Table 5 [RWQCB 2024a]). <br />Following gauging activities, the wells were purged and groundwater samples were collected. The samples were <br />submitted to Pace Analytical Environmental Services (Pace), located in Bakersfield, California, a state-certified <br />laboratory. The fourth quarter 2024 samples were analyzed for routine physical parameters (i.e., turbidity, <br />temperature, specific conductance, and pH) as stipulated in MRP Table 2 (RWQCB 2024a), and constituent <br />parameters as stipulated in MRP Table 3 (RWQCB 2024a). <br />Field data sheets are provided in Appendix B. Laboratory analytical reports and chain-of-custodies are provided in <br />Appendix C. <br />2.1.3 Analytical Results <br />Laboratory analytical results from the fourth quarter 2024 groundwater monitoring event are presented in Tables <br />3a through 3c. The volatile organic compound (VOC) data presented in the tables include results greater than the