Topic Area: 4c. Activated Carbon-Based PFAS Treatment Technologies

Formatted Title:

Colloidal Activated Carbon Barrier Pilot Test

Background/Objectives:

A large-scale pilot test is being conducted at Site 14, Alameda Point (Former Naval Air Station Alameda), California (site) to test the effectiveness of an in situ colloidal activated carbon (CAC) barrier to reduce the mass flux of per- and polyfluoroalkyl substances (PFAS) from migrating into the Oakland Inner Harbor. PFAS have been detected in groundwater at the site from the past use of aqueous film forming foam (AFFF) during firefighting drills.

The concentrations of PFAS in site groundwater range from 7.6 nanograms per liter (ng/L) to above 300,000 ng/L. Perfluorooctanesulfonic acid (PFOS) is generally present at the highest concentration, but a range of other typical PFAS (e.g., perfluorooctanoic acid [PFOA], perfluorobutanesulfonic acid [PFBS]) are present as are perfluoroalkyl acid (PFAA) precursors. Based upon PFAS concentrations, site geochemistry, geology and hydrology, as well as results from other laboratory and field tests, a CAC barrier was considered as a viable option to decrease PFAS concentrations in groundwater and reduce mass flux to the Oakland Inner Harbor.

Approach/Activities:

A total of 340,000 pounds of CAC, in the form of PlumeStop^®, was injected across 280 direct push injection points to create a 720-foot barrier parallel to the shoreline of Oakland Inner Harbor. To evaluate the effectiveness of the barrier, three transects consisting of two sets of nested wells were installed. One transect is upgradient of the barrier, one is on the downgradient edge of the barrier, and one singe well is downgradient of the barrier. Groundwater has been collected from these wells to evaluate changes in PFAS concentrations. Passive flux meters (PFMs) were installed in select transect wells before and after the installation of the barrier to evaluate changes in PFAS mass flux due to the CAC barrier.

Michael Lightner

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(Group 1, Poster Board #20) Colloidal Activated Carbon Barrier Pilot Test