Last week, in what may or may not be the last round in the ongoing efforts by Michael and Chantell Sackett to build a house on wetlands in Idaho, 
the 9th Circuit Court of Appeals found that:
EPA reasonably determined that the Sacketts’ property contains wetlands that share a significant nexus with Priest Lake, such that the lot was regulable under the CWA and the relevant regulations.
The history of the case is tortuous, entertaining, and altogether too long even to summarize adequately in a blog post. Suffice it to say that, after EPA’s rather humiliating defeat before the Supreme Court, and after the passage of seven years, the District Court ruled in EPA’s favor, finding the Sackett’s property was subject to CWA jurisdiction and that the issuance of EPA’s compliance order was not arbitrary and capricious.
The Sacketts appealed, but in the meantime, the Trump EPA withdrew the order and notified the Sacketts that it had no intention of taking any further action against them. When the Sacketts maintained their appeal, EPA moved to dismiss it as moot. However, the 9th Circuit concluded that EPA had not met the “heavy burden” required to establish mootness, because the withdrawal of the order was voluntary and not the result of any independent circumstance that would preclude EPA from changing its mind yet again in the future.
With mootness disposed of, the 9th Circuit turned to the merits – which means navigating the craziness environmental lawyers know as Rapanos. I will confess that I used to find the multiple opinions in Sackett entertaining; now I just want it to go away. Here, the 9th Circuit had ruled in 2007 that the Kennedy concurrence was the controlling rule of law. In this recent Sackett decision, the Court decided that there was no reason to revisit that holding.
From there it was fairly easy to conclude that it was not arbitrary and capricious under the “significant nexus” test to find that the Sacketts’ property was subject to CWA jurisdiction.
It seems to me that the Sacketts should have declared victory when EPA withdrew the enforcement order. They may be hoping to be a test case for SCOTUS, but I’ve never thought that this was a good case on the merits for conservatives to push. The facts are pretty much an advertisement in support of the significant nexus approach.
Which doesn’t mean that the Supreme Court won’t take the inevitable appeal or that SCOTUS won’t rule in the Sacketts’ favor if they do.
Having studied many of these situations for many years in the field, it is particularly vexing to see how little the various judges (including Kennedy and Scalia) were made to understand how variable the nexus is between any given wetland and significant harm to a WOTUS. It is very often determined by the arbitrary choice of what EVENT (or series of events) has been selected as the reference point-e.g., 25, 100, 500 year storm. A more frequently recurring event may move a significant amount of dissolved contaminants versus a much larger/more rarely recurring event moving contaminants bound to particulates. Further, site-specific chemistry determines how available the contaminants are to cause significant harm (e.g, is a toxic metal or nutrient bound up or ultimately available). It seems to me that an appropriate regulatory approach requires (unfortunately from an implementation standpoint) more data on these factors than time and budget often allow.