TASK 1 – Review of Work Completed by other State and Federal Agencies • Identify and summarize the published studies, models, and methods used by other state and federal agencies to evaluate PFAS leachability from soils to groundwater. • Identify and summarize the published studies, models, and methods used by other state and federal agencies to evaluate PFAS leachability from dredged sediments to groundwater. • Identify and summarize any site-specific or generic approaches implemented by other states or agencies to develop PFAS soil leaching screening levels, standards, or criteria. • Prepare a draft summary memorandum of all items in this task for EGLE/MPART review and comment. Present the findings of this task to EGLE/MPART at a virtual meeting within 14 calendar days after draft memorandum submittal. Address all comments to the satisfaction of EGLE/MPART within 14 calendar days of receipt of comment. Submit the final summary memorandum to EGLE/MPART for approval. TASK 2 - Review of Available Research and Models for Use in Michigan • Assemble, review, and summarize available national research and data on PFAS soils related to leaching of PFAS to groundwater, including predictive modeling for PFAS precursor mass in soils. • Review and summarize available models and methodology that can be used to predict PFAS leaching from soils. • Evaluate and summarize chemical, physical and geological specific inputs required for each model. • Evaluate the ability of the model(s) to include the full USEPA Method 1633 PFAS analyte list. • Evaluate the ability of the model(s) to predict PFAS concentrations in groundwater from soils contaminated by various PFAS sources (e.g., firefighting foams, electroplating waste, consumer products) considering the precursor mass that can reside in soils long term. • Perform a sensitivity analysis of the recommended top 3 models, as approved by MPART/EGLE. • Evaluate model limitations for the recommended top 3 models, as approved by MPART/EGLE, with respect to soil type(s), geology, PFAS concentrations, applicability to PFAS mixtures and precursor compounds, source of PFAS release, and relevant sources of uncertainty. • Recommend up to 3 models to be validated in Task 3. • Prepare a draft summary memorandum of all items in this task for EGLE/MPART review and comment. Present the findings of this task to EGLE/MPART at a virtual meeting within 30 calendar days after draft memorandum submittal. Address all comments to the satisfaction of EGLE/MPART within 30 calendar days of receipt of comment. Submit the final summary memorandum to EGLE/MPART for approval. TASK 3 – Validation of Recommended Model(s) Upon review of the information gathered from the previous tasks, EGLE/MPART may choose to conduct limited validation of the recommended model(s). This task shall commence only at EGLE/MPART’s request and only after all other tasks have been completed and approved. A lump sum has been set aside to provide a budget for such work. The initial phase of work will include validation of the model(s) against existing paired soil, groundwater, and/or leachate PFAS data. If requested, a second phase of model validation work may include collection of soil and groundwater PFAS data from select sites across the state, running the recommended model(s), and comparison of the actual analytical data to the model produced data, and developing conclusions.
