On March 24, 2021, the Pennsylvania Department of Environmental Protection (PADEP) announced that it issued an National Pollutant Discharge Elimination System (NPDES) permit to the Biddle Air National Guard Base (ANGB) (formerly the Horsham Air Guard Station) containing discharge limits of 70 parts per trillion (ppt) for the combined concentration of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), two common per- and polyfluoroalkyl substances (PFAS).  The permit authorizes the discharge of treated stormwater and groundwater from the site.  The site has long been the subject of investigation for volatile organic compounds.  In mid-2014, PFOA and PFOS were also found in drinking water wells near the site, and the Navy and Air National Guard, under United States Environmental Protection Agency (USEPA) oversight, continue to investigate PFAS in groundwater at and near the site.

This imposition of discharge limits is notable because PADEP has not yet promulgated a water quality standard for any PFAS, including PFOS and PFOA, and has not established effluent limits to achieve any such standard.  Based on its 2021 regulatory agenda, it is not clear whether DEP intends to promulgate any standard this year.  Under typical circumstances, a PADEP NPDES permit incorporates effluent limitations for specific parameters promulgated under Chapter 93 of PADEP regulations.

PADEP permits may also incorporate a general “narrative” criteria, which require that water not contain concentrations or amounts of substances sufficient to be “inimical or harmful” to the water uses to be protected or to human, animal, plant, or aquatic life. 25 Pa. Code § 93.6. The narrative criteria are often applied to floating materials, such as oil, grease, and scum.

Here, absent a promulgated water quality standard for either PFOA or PFOS, PADEP explained in its permit fact sheet that it relied on the general narrative water quality regulatory criteria to justify its PFOA and PFOS discharge limits in the ANGB NPDES permit.  Per section 93.6(b), “specific substances to be controlled include, but are not limited to, floating materials….”  25 Pa. Code § 93.6(b).  Here the narrative criteria are being used to set effluent limits for specific pollutants for which DEP has not yet promulgated an effluent standard.

The Horsham Air Guard Station appealed the Department’s NPDES issuance.  We will monitor that case as it progresses before the Environmental Hearing Board.

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