In psychology, the term “closure” refers to humans’ desire for a firm answer to a question and general aversion to ambiguity. Nine years since Rapanos, after multiple attempts by the EPA and the Army Corps (“the agencies”) to clarify the term through guidance, and after over 1 million public comments on a proposed rule, we all yearn for closure on the meaning “waters of the United States” (“WOTUS”). In the new WOTUS final rule just issued, the agencies attempt to once and for all settle the question of which waters and wetlands qualify for federal protection under the Clean Water Act (“CWA”).

Have the agencies expanded the scope of the CWA with the new rule? Clearly yes. By how much? Depends who you ask. The agencies believe positive jurisdictional determinations will increase negligibly (less than 5%), while industry critics and some legislators argue that the rule represents agency overreach on a massive scale. Likely, the truth lies somewhere between the two extremes.

Perhaps a better question to ponder is whether the rule adequately performs as advertised by more clearly defining WOTUS. Do regulated entities now have a workable standard to apply in determining whether they need to apply for CWA permits? Do regulators have a workable standard to apply in implementing the Act? Do the courts, if faced with new cases, have a functional rule to apply?

Yes, the rule provides more bright-line categories of waters that are jurisdictional, such as tributaries and adjacent waters, arguably providing greater clarity. It also for the first time provides needed definitions for regulatory terms like “tributary” and “neighboring.” It more neatly lays out the exclusions to WOTUS and treatment of certain types of features, like ditches, in a way that regulated industry should find helpful.

But no, the final rule will not eliminate all ambiguity. For some categories of potential WOTUS, the rule will perpetuate confusion.

For instance, the definition of tributary requires the feature to have “physical indicators of a bed and banks and an ordinary high water mark” and the Preamble to the rule indicates that the agencies can use historical indicators to ascertain if these exist. “Ordinary high water mark” is ambiguous and unevenly applied; use of historical indicators could easily lead to contradictory results. Likewise, the definition of “adjacent waters” includes “neighboring waters,” but to ascertain if a water is “neighboring,” one must first know its distance from the ordinary high water mark of a traditionally navigable water, interstate water, territorial sea, impoundment, or tributary, whether the water is located within a 100-year floodplain, and if it is within a certain distance from the high tide line of a traditionally navigable water, interstate water, or territorial sea. This information isn’t exactly captured on a website or map. These are technical, complex determinations that regulated entities are not in best position to make. Even sophisticated regulators will require up-to-date FEMA floodplain maps, modeling data, and manpower to make such determinations – all costing time and money.

And we haven’t even considered yet the most complicated categories of jurisdictional waters under the final rule! The agencies retain Justice Kennedy’s “significant nexus” test for two categories of waters. First, five subcategories of similarly situated waters (such as prairie potholes) are jurisdictional when they are determined, on a case-specific basis, to have a significant nexus to at traditionally navigable water, interstate water, or territorial sea. Second, the rule allows for case-specific consideration for waters located within the 100-year floodplain of a traditionally navigable water, interstate water, or territorial sea, and all waters located within 4,000 feet of the high tide line or ordinary high water mark of a tributary if they have a significant nexus to a traditionally navigable water, interstate water, or territorial sea. If this sounds confusing, that’s because it is!

Jurisdictional determinations under these last two categories face all the technical complexity of the tributaries and adjacent waters categories AND require a “significant nexus” determination – consideration of whether it is more than speculative or insubstantial that the feature in question would affect a function of a jurisdictional water that contributes to that water’s chemical, physical, or biological integrity.

The bottom line is that regulated entities and regulators will still need to spend substantial time and money to determine if certain waters are jurisdictional. Perhaps the agencies’ perceived need to square the new definition with Justice Kennedy’s fact-intensive significant nexus test guaranteed an outcome that is less than clear-cut. In the meantime, at least until the courts have at the final rule, true closure on the meaning of WOTUS remains elusive.