2024-766-E-Solid Waste-Draper Aden Associates-Orange County Regional Landfills Closed MSW Landfill Leachate PFAS Study

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Mr. Robert Williams December 6, 2024 – Closed MSW Landfill Leachate PFAS Study – Phase 1 Page 2 of 5 The wet well for PS #1 was “dry” for both 2023 and the Spring 2024 sampling events, but leachate was present in PS #1 during the Fall 2024 sampling event, conducted in mid-November. TRC had initially prepared a contingency plan to find alternative access points for sampling the leachate, but it appears the leachate may be sampled in a conventional manner from one or both sumps. TRC recommends we examine the Landfill Gas (LFG) production records, in pursuit of a better understanding of the causes for the leachate sump going dry. TRC also recommends performing a visual inspection of the landfill cover to detect potential maintenance needs. SCOPE OF SERVICES Task 1 - Site Visit and Records Review: TRC engineers and a sampling technician will visit the landfill with Facility staff to confirm that we can sample leachate at one or both pump stations and inspect the landfill cover for regulatory compliance, e.g., healthy vegetation, no erosion or obvious settling. We will request records for the leachate system and LFG production. TRC will prepare a list of field and laboratory analytes to detect whether PFAS compounds are present in the leachate, and if so, what chemical compounds and other characteristics are present that would affect treatability. Task 2 - PFAS Sampling Event: TRC’s experienced staff will conduct the leachate sampling and test key field parameters using specialized PFAS sampling protocols at one or both pump stations. TRC will deliver the samples to subcontractor Pace Analytical in Raleigh, NC (Pace), which will analyze the samples under strict chain-of-custody protocols. Pace will analyze the samples for PFAS using EPA Method 1633f with other constituents specified by NCDEQ and basic water chemistry. Task 3 - Reporting and Project Management: TRC will provide the Facility with a draft summary report for the sampling event. TRC will treat the data as confidential and review our findings with Facility management, prior to issuing any final reports. The report will describe in brief whether PFAS are present in the South Landfill leachate; if so, what specific PFAS compounds are present, and what other constituents are present that might affect treatability. This report will not be a full treatability study, whereas more data may be required. Please keep in mind the POTW will be facing similar concerns over the discharge of PFAS, and it makes sense for these entities to cooperate – this itself will drive some of the treatment effort needed by the landfill. This study will be left for a future Phase 2. Our report will provide an opinion on which of the many available technologies OCSWD may wish to evaluate further, pursuant to a full treatability study or a “proof of concept” field demonstration. We will provide Orange County with an opinion on order-of-magnitude treatment costs, based on what is known at the time. The content of this report can be better defined once the sampling data is in hand. TRC will make a brief statement concerning landfill cover maintenance issues, based on our observations. After reviewing the findings with OCSWD, TRC will finalize the report for your records and prepare the sampling data only for submittal to NCDEQ – only what is required. Other findings and preliminary recommendations are not required to be submitted. Docusign Envelope ID: 911DA9D6-C358-4231-B7E3-0443B926487C