Commercial Facility Soil and Groundwater PFAS Investigation
Terraphase was engaged to review the results of a per- and polyfluoroalkyl substances (PFAS) investigation conducted by a third-party consultant at a hospital property in Pennsylvania. Historical records indicated the site had previously discharged laundry wastewater (greywater) to a drain field south of the main facility, raising concerns about potential PFAS impacts to soil and groundwater.
Scope of Services
Terraphase’s services included the development and implementation of a focused soil and groundwater investigation at the property to replicate prior results and characterize the nature and extent of PFAS compounds in soil and groundwater. The ultimate goal for the site is to obtain a release of liability (ROL) under Pennsylvania Act 2 regulations that demonstrates attainment of a selected remedial standard.
Consistent with the initial investigation, six PFAS compounds: (perfluorooctane sulfonate [PFOS], perfluorooctanoic acid [PFOA], perfluorononanoic acid [PFNA], perfluorohexanesulfonic acid [PFHxS], perfluoroheptanoic acid [PFHpA], and perfluorobutanesulfonic acid [PFBS]) were targeted for analysis in soil and groundwater. Results confirmed the presence of PFOS, PFNA, and PFOA in both soil and groundwater, with additional PFAS (PFHxS, PFHpA, and PFBS) detected in groundwater. The investigation also identified PFOS and/or PFOA at concentrations above the respective Pennsylvania Department of Environmental Protection (PADEP) residential and non-residential medium-specific concentrations (MSCs) in multiple soil and groundwater sampling locations throughout the site.
Based on the results of the initial investigation, Terraphase developed, and is currently completing, a more comprehensive soil and groundwater investigation designed to fully characterize the extent of the PFAS impacts in soil and groundwater at the site. The comprehensive investigation will include evaluating the potential significance of human and ecological exposure to PFAS compounds in soil and groundwater to determine the need for remedial or risk management actions necessary to obtain an ROL.
Notable Accomplishments
- Verified and expanded on third-party PFAS findings with consistent results
- Identified exceedances of PADEP MSCs across multiple areas of the site
- Maintained rigorous quality assurance/quality control (QA/QC) protocols with no detectable contamination in control samples
Groundwater and Pore Water PFAS Investigation
Terraphase conducted the first investigations of per- and polyfluoroalkyl substances (PFAS) in sediment pore water in the San Francisco Bay, California. The study was initiated to address regulatory concerns about potential migration of PFAS into the bay from shallow groundwater at an industrial facility, potentially impacting aquatic receptors.
Scope of Services
Terraphase performed hydrogeologic investigations, including a tidal influence study and slug testing, to develop a conceptual site model and estimate the groundwater discharge zone. Pore-water samples were collected at two depths from 12 locations along 6 transects perpendicular to the shore, between 5 and 50 feet offshore, using a custom-modified, PFAS-free Trident probe. PFAS concentrations in pore water were compared to regional background values and ecological screening criteria.. Data were used to calculate dilution-attenuation factors (DAFs) and to propose site-specific groundwater screening levels for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), which were accepted by the San Francisco Bay Regional Water Quality Control Board (RWQCB).
Notable Accomplishments
- Completed the first PFAS pore-water investigation in the San Francisco Bay
- Identified no exceedances of PFAS aquatic-receptor screening criteria in pore water
- Demonstrated attenuation of PFAS from groundwater to sediment pore water
- Calculated site-specific DAFs for PFOS (33) and PFOA (10)
- Developed and received regulatory acceptance of site-specific groundwater screening levels
Brownfield PFAS Investigation
Terraphase provided remediation services at an industrial site in New York. The site is enrolled in the New York State Department of Environmental Conservation (NYSDEC) Brownfield Cleanup Program (BCP), a remedial program governed by 6 NYCRR Part 375. In accordance with program requirements, the site investigation included evaluation for per- and polyfluoroalkyl substances (PFAS).
Scope of Services
Terraphase prepared and implemented a Remedial Investigation Work Plan addressing PFAS sampling in soil and groundwater using U.S. Environmental Protection Agency (USEPA) Method 1633. Soil samples were collected via GeoProbe® direct-push technology using PFAS-compatible materials in accordance with NYSDEC guidance. Groundwater samples were obtained from permanent on- and off-site monitoring wells using low-flow sampling techniques and PFAS-compatible polyethylene tubing. While no historical PFAS usage was documented at the site, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were detected in one soil sample below the unrestricted use threshold. Groundwater samples showed PFAS concentrations above New York fresh groundwater (Class GA) ambient water quality standards, though these are considered consistent with known regional background levels in the Bronx and New York City area. NYSDEC will make a final determination following review of the Remedial Investigation Report.
Notable Accomplishments
- Conducted PFAS soil and groundwater sampling in accordance with NYSDEC 2023 guidance
- Supported regulatory compliance under the NYSDEC Brownfield Cleanup Program
