In the Twin Cities East Metro region of St. Paul Minnesota, PFAS contamination has been identified across surface water, in groundwater, and in drinking water aquifers that serve multiple local communities. Under contract with the Minnesota Pollution Control Agency (MPCA), we developed an understanding of how contamination originating from historic disposal sites was moving through an engineered flood control system — and how that system was contributing to a regional spread of PFAS.
The stormwater management project, named Project 1007, was constructed in the late 1980s, and extends approximately 14 miles traversing waterways through multiple communities. Project 1007 includes open channels, pipes, storm sewers, dams, and interconnected surface and groundwater features. The purpose of Project 1007 was to provide flood protection, but its scale and connectivity raised a critical question: was the system also acting as a regional pathway for PFAS, allowing the spread of upstream contamination to drinking water wells?
MPCA faced complexities inherent to substantial legacy contaminant releases that were able to traverse a very large area via water infrastructure systems. PFAS migrated horizontally and vertically, transiting the built infrastructure across watershed boundaries, groundwater divides, and through multiple aquifers. Impacts extended far beyond a single site, requiring a robust investigation and comprehensive interpretation of multiple types of data that could withstand regulatory and public scrutiny and inform long-term decision making — without compromising flood control operations relied upon by communities facing combined flood management and PFAS challenges.
Comprehensive characterization across a 120-square-mile impacted region
We were engaged to deliver a large-scale PFAS assessment and feasibility study focused on understanding PFAS sources, pathways, and receptors across the 120-square mile region around the Project 1007 corridor. The work was structured to answer regional questions first and develop greater detail where necessary to support and advance remedial decisions.
The team conducted extensive investigation and characterization efforts for PFAS from multiple primary historical and secondary transported sources. AECOM teams sampled soil, sediment, surface water, surface water foams, biota, and groundwater across the region detailing PFAS impacts throughout the project area.
At the core of the program was the development and continual refinement of a comprehensive conceptual site model (CSM). This model integrated surface water conveyance, groundwater flow, and surface-to-groundwater interactions into a single, coherent geologically structured framework. It provided MPCA with a defensible, systemwide understanding of how PFAS migrates through both natural and engineered pathways — a distinct advantage using a watershed approach to a regional-scale problem.
“This feasibility study points the way forward with options for a more robust environmental cleanup to remove PFAS from surface water and groundwater while preventing the East Metro PFAS plume from spreading further.” –MPCA Official
Tracking PFAS vertically and horizontally across multiple aquifers and watersheds
The complexity of the investigation reflected the scale of the system. PFAS transport had to be evaluated across multiple depths, geologic units, and hydrologic conditions. Deep bedrock monitoring wells were installed using sonic drilling and vertical aquifer profiling to accurately define contaminant movement within and between aquifers. Sampling methods varied from deep groundwater pumping to surface water and biotic sampling, all designed to determine clear linkages between surface water features and drinking water aquifers. Taken a step further, planned forensic PFAS analysis will decipher unique chemistry signatures and defined zones of mixing from two primary historic source areas.
AECOM fully integrated surface water, groundwater, and PFAS fate-and-transport modeling with the complex CSM. We transcended limitations inherent to isolated local datasets and synthesized regional trends, time dependent movement, chemical changes in PFAS signatures, and the influence of the conveyance system as a whole. Calibrated against current conditions, collectively, these models offered predictive information on PFAS transport over the next 50 and 100 years, which was essential to guide long-term remedial solutions and region-wide decision-making.
Bench scale and pilot studies were incorporated to test separation and destruction technologies, positioned to inform feasibility-stage decisions. The field pilot was focused on near-source PFAS contaminated surface water and groundwater as one part of the overall remedial solution for the entire impacted East Metro. These tests were conducted while maintaining an investigation emphasis on understanding the system, reducing uncertainty, and identifying where intervention would be most effective if pursued. Our field pilot study results were released to the public by MPCA in May 2026 in the “Project
1007 Feasibility Study.” One component of the field pilot was focused on removing and concentrating PFAS from surface water and groundwater near a source. The efforts were successful in removing long-chain target PFAS by more than 95% and concentrating PFAS by 3 to 6 orders of magnitude. AECOM and other contractors further tested the performance of five types of PFAS destruction technologies on the concentrate. We also performed bench-scale testing, including rapid small-scale column tests (RSSCTs), to evaluate PFAS removal on water further from the source areas where drinking water protection is necessary.
The Feasibility Study performed a complete alternatives analysis, incorporating results from pilot and bench studies, to recommend a remedial alternative for East Metro. The feasibility study recommended source zone control to protect from ongoing migration, groundwater well extraction and treatment systems to provide safe drinking water supply, surface water treatment with in-situ permeable absorptive barriers to protect sediment, access restrictions to highly affected areas, and long-term monitoring of the cleanup.
Reduced uncertainty for long-term planning, funding, and regulatory decisions
The program delivered a systemwide, evidence-based understanding of PFAS movement across a large regional infrastructure network. The integrated conceptual site model and modeling framework clarified how PFAS travels from historic source areas through surface water and groundwater pathways, and how the flood control system contributes to downstream transport.
This work underpinned feasibility stage evaluations and targeted remedial concepts, including options designed to limit plume migration and support long-term groundwater resource protection. Importantly, the investigation informed decisions affecting drinking water aquifers serving multiple East Metro communities, using a consistent and defensible technical foundation.
This in-depth study created a shared understanding among multiple governing agencies managing water, infrastructure, and public health concerns across the region.
A replicable framework for managing PFAS in complex water systems
PFAS challenges increasingly intersect with large, aging infrastructure systems. Project 1007 demonstrates why watershed scale investigations are essential where flood control, surface water management, and drinking water protection overlap.
The methods applied — targeted PFAS characterization, integrated modeling, and a comprehensive conceptual site model — provide a replicable framework for other agencies facing PFAS impacts across complex conveyance systems.