Owners of septic systems and other nonpoint sources of pollutants should be quaking in their boots.

The Clean Water Act’s regulatory program only addresses discharges of pollutants to navigable waters from point sources, defined as “any discernible, confined and discrete conveyance.” In 2020, Justice Breyer, writing for six justices, held the Clean Water Act regulates a direct discharge from a point source and a discharge that is the “functional equivalent” of a direct discharge. County of Maui v. Hawaii Wildlife Fund, et al., 140 S. Ct. 1462 (2020). He then identified seven non-exclusive factors for courts to consider when determining if something is functionally equivalent.

On July 15, 2021, on remand from the Supreme Court, the District Court for the District of Hawaii relied on the following facts to determine that a discharge into the injection well at issue in the Maui case, which is permitted under the Safe Drinking Water Act, is functionally equivalent to a direct discharge to navigable waters and therefore is regulated under the Clean Water Act:

• evidence of a hydrologic connection between the injection wells and coastal waters,
• evidence that at least 2 percent of the wastewater from the wells reaches the ocean through identified seeps and of that amount, some reaches the ocean in 84 days, 50 percent reaches the ocean in 300 days, 70 percent reaches the ocean in 400 days, and 90 percent reaches the ocean in 600 days,
• evidence that the wastewater enters a shallow groundwater aquifer about 200 feet below the well and upon mixing with groundwater flows through the aquifer as diffuse flow and reaches the ocean after traveling from 0.3 to 1.3 miles, and
• expert testimony that all waters that infiltrate the soil on an island ultimately find their way to the sea.

The court agreed that the discharge that reached the ocean was diffuse and it was not clear where 98 percent of it entered the ocean. Further, the court agreed that the diffuse flow passed through rock and other substances and changed chemically as it moved through the aquifer. According to the U.S. District Court for the District of Hawaii, these facts did not preclude a determination that the discharge is the functional equivalent of a direct discharge into navigable waters.

In reaching its decision, the court focused attention on the volume of pollutants rather than its means of conveyance, specifically holding that diffuse flow is functionally equivalent to a direct discharge. Diffuse flow is the opposite of channelized flow and is a fundamental characteristic of a nonpoint source. However, under Maui and under the district court opinion, you could tag almost any source of pollution with a point source label.

The court’s analysis presents risks to all nonpoint sources. Septic systems on Cape Cod, in Key West, and along the shores if Wisconsin lakes present similar fact patterns. Undoubtedly millions of others do as well. There also are untold examples of other diffuse flows of pollution that may reach navigable waters. The source of the pollution may be a pile of dirt, a smokestack, a car that leaks oil onto a parking lot, a stormwater pond that relies on groundwater infiltration, or an aquifer storage and recharge system. Both Maui and the district court decision leave no principled way to distinguish these sources from the underground injection wells at issue in Maui. Eventually, this issue will have to return to the Supreme Court.