Theme: 07. Per- and Polyfluorinated Alkyl Substances (PFAS)

Topic Area: 7m. PFAS Site Characterization

Formatted Title:

Groundwater PFAS Characterization of an Oil Storage and Distribution Site with Multiple Secondary PFAS Sources

Background/Objectives:

Oil refining operations were first implemented in the area of the site in the late 1800s and the site currently covers approximately 450 acres. Operations include bulk petroleum storage/transfer and the facility is located in a highly industrialized urban setting. Aqueous film forming foam (AFFF) containing per- and polyfluorinated alkyl substances (PFAS) have been widely used at the site.

The formulations of AFFF have changed throughout the history of the site which initially used legacy perfluorooctanesulfonic acid (PFOS). As modern fluorotelomer manufacturing process began, the AFFF was transitioned to fluorotelomer-based AFFF containing long-chained fluorotelomers or C8 AFFF. This foam has been replaced with C6 fluorotelomer based foams currently used for firefighting at the site.

Throughout historic operations at the facility, AFFF has been discharged to address various fires, releases and testing of the fire suppression systems. When released, the AFFF either infiltrates into the ground or runs across impervious surfaces to the stormwater management system, which depending on groundwater levels can be an exfiltration source further downgradient from the release. In addition to AFFF, other regional sources of PFAS to the site include an offsite historical landfill, an offsite former fluoro-chemicals manufacturing facility, which among other thing incinerated PFAS materials, as well as other anthropogenic background sources (i.e., precipitation).

Approach/Activities:

The site geology consists of a layer of artificial fill containing a mixture of sand, sit, clay and gravel which generally sits above a low permeability clay layer. Below the clay layer is an unconsolidated layer of glacial till, glaciolacustrine clay and glacial fluvial deposits. Bedrock lies between approximately 25 and 135 feet below ground surface (bgs). The water table is typically found in the fill deposits.

To characterize PFAS impacts to groundwater, samples have been collected from over 150 monitoring wells screened at three different depths within the unconsolidated deposits at the site. Additionally, samples of rainwater and currently used AFFF were analyzed to provide a baseline for a contemporary background source and a C6 AFFF source.

The groundwater analytical data were evaluated against groundwater samples collected from the fluoro-chemical manufacturing site, samples collected near the landfill and samples collected from the up-gradient portions of the site to determine how these sites have attributed to groundwater PFAS concentrations at the site.

Results/Lessons Learned:

The groundwater PFAS sampling results indicate several different distributions of PFAS compounds are present at the site. The groundwater data provide evidence of impacts associated with legacy PFOS AFFF, legacy fluorotelomer AFFF and current C6 fluorotelomer AFFF. The groundwater has also been impacted with PFAS from the former fluoro-chemicals manufacturing facility. Up-gradient portions of the site are impacted with PFAS constituents at concentrations greater than groundwater standards from both background and secondary sources. Remediation efforts to the required regulatory standards will be potentially hampered by a long-term continual source of PFAS from precipitation.

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Ashley Korin