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Brendan Kenny Central Valley Regional Water Quality Control Board July 15, 2025 In accordance with the WDRs in the Order, the GWTS effluent limit for VOCs was not detected above the practical quantitation limit. Given the results from all effluent samples collected, the GWTS was compliant with the WDRs during the reporting period. Details regarding influent and effluent sampling, field sheets, and copies of the laboratory reports are provided under separate cover in the Second Quarter 2025 Groundwater Treatment System Monitoring Report and will be submitted by July 30, 2025. Residential Treatment Systems During the reporting period, Forward continued to provide operation, monitoring, and maintenance for 14 residential GWTSs on Austin and Newcastle Roads. The treatment systems are composed of inline sediment filters and dual GAC vessels that remove VOCs from the water prior to the water entering the residences. Regular system sampling and maintenance on the treatment systems are performed by Del -Tech. The effluent sample concentration limit for VOCs at each residential GWTS was non -detect. All residential GWTSs were in compliance with this effluent limit during the reporting period. A separate summary report for the residential GWTSs is prepared quarterly and the results for the reporting period will be submitted by August 1, 2025. Landfill Gas Collection and Control System During the reporting period, the landfill GCCS at the Site was monitored by a network of landfill gas extraction wells. The landfill gas collected from these wells is routed and split between two onsite flares (FL -100 and FL - 150) and the onsite landfill gas -to -energy plant operated by Ameresco. Flares FL -100 and FL -150 were previously reported as Flare A-2 and Flare A-3, respectively. The landfill gas extraction wells are monitored bi-weekly by SCS Field Services (SCS) of Modesto, California and reported by Geosyntec Consultants (Geosyntec) of Oakland, California. The SCS bi-weekly monitoring results for point -of -compliance wells and individual wells are included in Tables 1 and 2 of Geosyntec's Second Quarter 2025 Corrective Action Program Update, which is included as Attachment 2. VOCs were detected at concentrations ranging from 600 parts per billion by volume (ppbv) in gas probe GP-1AD to 6,200 ppbv in gas probe GP -10M (Attachment 2, Table 1). The CAO requires annual VOC analysis by United States Environmental Protection Agency Method TO -15 for any probe with methane concentrations exceeding 1 percent by volume and/or VOC concentrations exceeding 10 ppbv. On April 30, 2025, three gas probes (GP -1 OD, GP -10M, and GP -10S) had exceedances of methane greater than one percent by volume. In addition, 12 gas probes (GP-1AD, GP-1AM, GP-1AS, GP-2AD, GP-2AM, GP-2AS, GP-6AM, GP-6AS, GP -10D, GP -10M, GP -10S, and GP -11 S) had VOC concentrations above 10 parts ppbv. As a result, these 12 probes will require annual sampling and analysis of VOCs using Method TO -15. The next annual sampling event will be performed no later than November 30, 2025. In addition, the landfill GCCS undergoes periodic maintenance and tuning to produce the highest percentage of landfill gas and to minimize the collection of oxygen. The general operation of the landfill GCCS during the reporting period is documented by Geosyntec (Attachment 2). During the reporting period, the average flow rates to flares FL -100 and FL -150 were 1,544 and 1,406 standard cubic feet per minute (scfm), respectively. Except for standard flare malfunctions or shutdowns, the landfill GCCS operated continuously (24 hours per day) without any significant downtime. A summary of operation time for FL -100 and FL -150 is provided below: • Flare FL -100 had a total run time of 708.73 hours and a total downtime of 11.27 hours in April 2025, a total run time of 725.93 hours and a total downtime of 18.07 hours in May 2025, and a total run time of 694.78 www.arcadis.com 3/4 Forward Landfill 2Q25 CAP Update_ 07152025_ draft OFC Comment