Historic releases of process solutions resulted in elevated concentrations of volatile organic compounds (VOCs) in soil and groundwater at the site. As part of Michigan’s Industrial Pretreatment Program, water samples were collected from the site’s wastewater treatment system sump that had been treating the water for VOCs. Each of these samples detected PFOS at concentrations of 4,000-6,000 ng/L, which is greater than allowable discharge limits.

AECOM successfully negotiated with regulators to develop a reasonable and cost-effective path forward to protect human health. The team designed and installed an automated interim PFAS treatment system that effectively removes PFAS concentrations to non-detectable levels before being discharged to the sanitary sewer. The team completed subsurface evaluations to characterize, delineate and map the extent of PFAS impact, and also studied the potential fate and transport of PFAS off-site. A desktop evaluation reviewed the facility’s past use and products produced, and the team performed a forensic analysis to determine PFAS families of those chemicals. The forensic evaluation resulted in the identification of on-site and off-site sources, as well as CSM development for PFAS migration at the facility.

AECOM designed geological cross sections to evaluate vertical and lateral extent of impact and developed a working conceptual site model for the facility. A remedial alternatives evaluation determined the most cost-effective approach would be an in-situ sorption barrier. A groundwater treatability study evaluated the optimal dose response of varying grades of colloidal carbon for sequestration of PFAS. The study evaluated optimal dosage for in-situ injections of colloidal carbon as a barrier technology to inhibit off-site migration of PFAS. The results of the initial evaluation were successful, a second bench scale and tank study was performed, and a field pilot study was undertaken in 2020, with full-scale implementation scheduled for 2021.