Proposed "Waters of the U.S." Rule: Can Significant Nexus Be Clarified?

On March 31, we discussed that, at best, EPA's and the Corps' proposed rule defining what waters fall under federal jurisdiction provides only partial clarity.  The agencies have done little to clarify the circumstances in which there is no federal jurisdiction.  They have done more to clarify when they do have jurisdiction.  But is the proposed rule clear enough?

Recall that this question relates to the first of the two jurisdictional tests, which we discussed last Thursday - that a water is jurisdictional if is adjacent to tributaries of navigable waters.  Digging deeper into this test, the question is whether it provides any useful, additional clarity on top of that already provided by Justice Kennedy's opinion in Rapanos.

The test is based on two new definitions - of floodplain and riparian area.  If a water is in one of these two areas, it is considered adjacent and therefore jurisdictional.  The definition of floodplain is somewhat confusing and that of riparian area is completely opaque.   Perhaps recognizing this, the agencies have specifically asked for comments on both terms.

What Is a Floodplain?

First, the definition of floodplain.  The rule defines it as "an area bordering inland or coastal waters that was formed by sediment deposition from such water under present climatic conditions and is inundated during periods of moderate to high water flows."  Setting aside the question of what are "present climactic conditions" and whether that represents years, decades or an epoch, the larger problem is that the agencies' description of "moderate to high water flows" is not common floodplain parlance.  The Federal Emergency Management Agency identifies 100-year floods, 5-year floods and the like, but EPA and the Corps have chosen not use these already defined and fairly specific delineations.  Instead, the agencies have intentionally selected a malleable standard.  In the preamble to the proposed rule, the agencies acknowledge that:

There is, however, variability in the size of the floodplain, which is dependent on factors such as the flooding frequency being considered, size of the tributary, and topography. As a general matter, large tributaries in low gradient topography will generally have large floodplains. . . whereas small headwater streams located in steep gradients will have the smallest floodplains. It may thus be appropriate for the agencies to consider a floodplain associated with a lower frequency flood when determining adjacency for a smaller stream, and to consider a floodplain associated with a higher frequency flood when determining adjacency for a larger stream. When determining whether a water is located in a floodplain, the agencies will use best professional judgment to determine which flood interval to use (for example, 10 to 20 year flood interval zone).

In other words, the agencies have elected to define floodplain so that its size will vary from case-to-case, reducing clarity.

What Is a Riparian Area?

The meaning of the term riparian area is even harder to divine. The agencies define it as

an area bordering a water where surface or subsurface hydrology directly influence the ecological processes and plant and animal community structure in that area. Riparian areas are transitional areas between aquatic and terrestrial ecosystems that influence the exchange of energy and materials between those ecosystems.

None of the associated terms, like "ecological processes" "plant and animal community structure" or "exchange of energy and materials" are defined.  Nor, for that matter, is the "area" of the necessary structure, which creates a circularity - one must look at an unidentified ecological "area" to determine the riparian "area."

The most impenetrable phrase, though, is the area's "ecological processes and plant and animal community structure." All areas, upland and wetland, have such processes and structures.  Where one begins and one ends can border on the metaphysical.

Perhaps more unfortunately, this test is no more clear or  more expeditious than the eight-year old "significant nexus" test, discussed yesterday and which this test is supposed to clarify.  Identifying an area whose hydrology directly influences the ecological processes and plant and animal community structure in an area will have to be done case-by-case, just like the current significant nexus test.  And how to do so is no more obvious than how to identify an area under the significant nexus test that has chemical, physical and biological impacts on a downstream water.

Thus, in the end, the Agencies have provided two tests in order to clarify the "significant nexus" test.  One is the significant nexus test itself.  And the other is no more clear or expeditious.

This is the fifth in a series of posts regarding EPA and the Corps' proposed rule redefining "waters of the United States" under the Clean Water Act.

Photo credit: Nelson Minar / Foter / CC BY-SA