Formatted Title

3M Settlement Project 1007 Source Assessment and Feasibility Study Findings: Regulation and Resource Protection

Background/Objectives

Two of the oldest PFAS source areas in the world are located in the East Metro area of the Twin Cities region of Minnesota. The source areas contain identifiable blends of PFAS industrial waste, dumped in a wetland and unlined landfill setting dating back 70 years ago. The two source areas have leached impacts conveyed via surface water and groundwater pathways since that time, transforming into terminal, mobile and persistent PFAS plumes in complex hydrogeologic settings.

Impacts span more than 120 square miles from these two source areas, presenting challenges for sustainable natural resource protection, planning and cost implications. Under the 2018 3M Settlement with the State of Minnesota, a Source Assessment and Feasibility Study resulted in a robust multi-media data set and long-term drinking water resource protection considerations for decision-makers and residents of the region. Results of this work include bench- and field-scale pilot studies for PFAS remediation in surface water and groundwaters. The study aimed to inform regulators, governing bodies and citizens alike to understand the breadth of impacts, potential remedial options and cost impacts for current and future generations under the auspice of evolving human and ecological health knowledge.

Approach/Activities

This five-year study included an expedited approach to site characterization, integrated monitoring across media in foam, surface water, sediment and throughout six regional aquifers to inform the regional conceptual site model. Contaminant analysis combined statistical evaluations, analytical forensics and manufacturer-specific data for signature identification. An ecological risk assessment including species sample collection was completed for aquatic and terrestrial receptors. Hydrogeologic data were used to develop a combined surface water and groundwater numeric model, integrating site-specific fate and transport parameters into the transient mode of the model. Pilot studies were conducted to understand interim corrective action options using physical removal and concentration of PFAS in the environment followed by destructive technologies testing from eight individual technology vendors including electrochemical oxidation, plasma, supercritical water oxidation and photochemical technology types. The study addressed potential regional groundwater remediation options by evaluating regional-scale pump and treat systems that could provide multiple municipal supply demands. This was coupled with a managed aquifer recharge component and informed by site-specific injection capacity and geochemical studies.

Results/Lessons Learned

This study provides a comprehensive understanding of the impacts to human health, ecosystems and the environment from historic PFAS disposal. It goes further to demonstrate potential options for reducing impacts at the source areas and downstream in various media through pathway interruption and harnessing physical removal and destruction technologies. The study informs decision-makers with options for providing safe drinking water supplies to impacted area communities, protect drinking water resources for future generations and estimates the financial burden to reduce the continued spread of PFAS in the region. The final Feasibility Study Report and supporting studies are anticipated to be complete by the end of Q1 2024.