Functional Equivalence and NPDES Implications to Groundwater Discharges

A lot can change in a year! Since the Maui Decision and EPA Draft Guidance issued in December 2023, many of us have wondered what the implications will be to stormwater infiltration basins, injection wells, and NPDES Permitting in general. What have we learned and what happens next? Let's talks about forever chemicals, universal pollutants and pollutant forensics. This session will be interactive, so bring your stories and lessons learning!

Full Abstract: The discharge of pollutants to groundwater through infiltration or injection can result in the transport of unaltered pollutants back to surface water resources. The County of Maui was sued by the Hawaii Wildlife fund for a fully permitted injection of domestic wastewater into the subsurface through injection well that, due to the local geology and groundwater flow characteristics, unintentionally released harmful concentrations of pollutants to the Pacific Ocean in violation of surface water quality standards. As a result, the EPA and authorized NPDES permit authorities must now consider other situations where groundwater and surface water communication can result in degradation of a surface water resource.
This session will review the legal history of the Maui Decision and the scope of the Functional Equivalence guidance issued by EPA. A review of the factors to be considered in a functional equivalence determination with be presented. Additionally, we will review geologic structures that can enhance the fate and transport of pollutants through the groundwater to surface water pathways.
Implications of the Maui Decision on specific regions in the United States will be discussed. Karst terrain environments, unconfined, sand and gravel aquifer systems, and proximity to surface water resources can trigger the need for a deeper review of pollutant movement in the subsurface. What information does an applicant need to consider in the permitting and how does one comply with groundwater protection criteria in addition to surface water quality standards?
The presentation will review of a few local ordinances, including Bowling Green Kentucky and Spokane Washington, that have already built groundwater protectiveness criteria into stormwater infiltration design standards to mitigate for pollutant transport. Join this discussion to identify the trends in regulations, the affected design criteria, and some mitigating factors that designers and permittees should consider to protect water resources in the United States.
Want to know more? We will also discuss the PFAS/PFOA regulations for stormwater and wastewater discharge. This ubiquitous substance can be found in most influent waters, as a residue, in soils, containers, and wastes, and in our wastewater flows. With the permanent nature of the chemical compounds in nature and the difficulty in controlling the source, testing for and treating to the action levels, and the ongoing demand from regulators to reduce the impact to water sources, what can NPDES permittees expect to see in our permits and Best Management Practices? How does functional equivalence bear on PFAS contaminant tracking? In this brief review of this specific pollutant in the context of functional equivalence, we can shed some light on the nature and impact of connected water resources and the need to carefully manage stormwater in a changing world.