How We Reduced PFAS-Impacted Groundwater Migration by up to 99% at the Oakland Inner Harbor

THIS WEEK’S CONTRIBUTOR:
Laura McNamara, PE, PMP | Sr. Director of Environmental Labs & Installation Management
APTIM | Remediation & Technical Solutions
Laura.McNamara@APTIM.com
Laura has more than 23 years of experience performing and managing environmental investigation and remediation projects across the US for the Air Force, Army Corps of Engineers, and Defense Logistics Agency. She is an expert in PFAS investigation, treatment, and management to protect the health of our clients’ environments and communities.

How We Reduced PFAS-Impacted Groundwater Migration by Up to 99% at the Oakland Inner Harbor

Historical firefighting training at the former Naval Air Station (NAS) Alameda in California led to the release of per- and polyfluoroalkyl substance (PFAS) resulting in impacts to groundwater at the site. The historical release(s) have led to these persistent substances migrating toward the Oakland Inner Harbor, posing a potential risk to aquatic ecosystems. Because viable in-situ methods to destroy PFAS remain elusive, effective strategies for adsorption and sequestration are critically important—and we are proud to have delivered those here.

Thank you to my APTIM teammates (Nels Johnson, Robert Mayer, Michael Lightner, and Paul Hatzinger) and our partners at Bayside Engineering Construction (Abram Eloskof, Gary Cronk, and Sridhar Palakur) and Regenesis (Craig Sandefur and Dan Nunez) for their collaboration on this innovative project itself and the synopsis of our work below, broken down in three key stages.

Stage 1. Investigate Extent of PFAS Contamination

APTIM, in collaboration with Bayside Engineering Construction and Regenesis, undertook pioneering research at Installation Restoration (IR) Site 14 to address impacts caused by PFAS-containing firefighting foams used at NAS Alameda. The team developed a 720-foot permeable adsorptive barrier (PAB) utilizing colloidal activated carbon (CAC). This barrier was specifically designed to intercept and significantly reduce PFAS-impacted groundwater migration toward the harbor.

Initial groundwater assessments at IR Site 14 revealed PFAS concentrations substantially above the Department of Defense (DOD) screening standards, including levels up to 1,100,000 nanograms per liter (ng/L) for perfluorooctanoic acid (PFOA) and 302,000 ng/L for perfluorooctane sulfonic acid (PFOS). These initial findings triggered the completion of an initial extensive remedial investigation, ultimately leading to the selection and pilot testing of CAC technology to provide an interim remedial measure to address the migration potential of PFAS from site groundwater to the Inner Harbor.

Stage 2. Develop Customized PFAS Remediation Innovation

The chosen CAC solution, commercially available as Plumestop®, involves injecting a polymer-stabilized suspension of fine activated carbon particles into the aquifer. These particles adhere strongly to subsurface sediments, greatly enhancing their capacity to adsorb PFAS without significantly affecting groundwater hydraulics. Essentially, CAC creates a subsurface filter that immobilizes contaminants, preventing further downstream migration. Compared to conventional pump-and-treat approaches, CAC is both more sustainable and energy-efficient.

To maximize the effectiveness of the barrier, detailed pre-design evaluations were conducted. These included laboratory column tests conducted in APTIM’s Lawrenceville, New Jersey, laboratory, soil coring analyses, and groundwater sampling. Passive flux meter studies further quantified the contaminant mass flux. Initially, the barrier design was based solely on groundwater flux. However, incorporating additional considerations, such as soil back-diffusion, nearly doubled the initial CAC dosage estimate. This underscores the critical importance of thorough site characterization in remediation efforts.

The final PAB design recommended by APTIM and implemented by the team included variable CAC dosage, ranging from 2.5% to 7.5%, calibrated to match the contaminant levels along the barrier’s length. The design also accounted for existing storm sewer infrastructure to prevent injected CAC from discharging into the Harbor during installation. The CAC was injected using direct-push technology at depths between 1 and 15 feet, effectively targeting the contaminated groundwater zone. Real-time monitoring allowed for adaptive management, promptly addressing challenges such as variations in soil permeability.

Stage 3. Monitor PFAS Contaminate Reduction

Post-installation monitoring included quarterly sampling from 18 strategically positioned groundwater wells. Four monitoring events revealed significant PFAS concentration reductions. Within the barrier itself, concentrations of PFOS and PFOA dropped by more than 99%. Downgradient wells experienced reductions ranging from 40% to 99%, affirming the barrier’s substantial capability to prevent PFAS migration toward the Oakland Inner Harbor.

Mass flux analyses further confirmed the barrier’s efficacy, indicating substantial reductions in PFOS flux. Despite minor variability attributed to tidal effects, overall results strongly support the successful sequestration of PFAS contaminants within and downgradient of the treatment zone. The project was executed efficiently, within 11 months of contract initiation, maintaining schedule and budget constraints and exemplifying effective project management and technical proficiency.

The Alameda site results compellingly demonstrate CAC’s potential as a groundwater migration and mitigation remediation approach. This innovative field test highlights the broad applicability of CAC technology, offering a promising, cost-effective alternative to traditional groundwater remediation methods for DOD installations and beyond.

APTIM’s PFAS Solutions: From Flask to Field

With APTIM’s Flask to Field™ PFAS services, we are poised to support clients with investigations, evaluation and testing of possible remedies, selection of the most appropriate actions, and implementation and monitoring. Partner with us today to achieve long-term protection of human health and the environment.

Published in June 2025