by Austin Zen, ENV SP
Navigable Waters Protection Rule (NWPR), published on April 21, 2020 and effective on June 22, 2020, provides a new definition of “waters of the United States” (WOTUS) for the purposes of the Clean Water Act (CWA). The rule seeks to create more clarity regarding which wetlands are federally regulated – viewed as WOTUS – and which wetlands are merely wetlands not subject to federal protection.
CWA directs the U.S. Environmental Protection Agency (EPA) and the Department of the Army (Army) to protect “navigable waters” from the discharge of pollutants, including the placement of fill material to support the construction of infrastructure or development projects; however, it does not clearly define WOTUS. This lack of clarity has resulted in decades of debate and confusion over its scope. Disputes over federal regulation – known as “jurisdiction” – often end up in court, sometimes the U. S. Supreme Court. These key decisions (notably United States v. Riverside Bayview, SWANCC v. U.S. Army Corps of Engineers, and Rapanos v. United States) sometimes help to provide additional clarity, but sometimes these decisions create more confusion.
The NWPR is the latest attempt to clarify the definition of WOTUS and it makes the following key changes to the scope of WOTUS:
- Ephemeral features – waters that “flow . . . only in direct response to precipitation (e.g., rain or snow fall)” were sometimes viewed as WOTUS are now excluded from federal jurisdiction in all cases.
wetlands, which were viewed as WOTUS, are now only jurisdictional if:
- they abut (touch at least one point or side) a WOTUS;
- it is inundated by flooding from a WOTUS in a typical year; or
- it is physically separated by specific natural features or artificial structures while maintaining a direct hydrologic surface connection with a WOTUS in a typical year.
which were generally not jurisdictional, can be jurisdictional if they satisfy
these flow conditions (perennial or intermittent in a typical year)
- relocate a tributary;
- are constructed in a tributary; or
- are constructed in an adjacent wetland.
- Significant Nexus is no longer used for determining jurisdiction.
- Non-jurisdictional features are defined.
You may have noticed that the term “typical year” is a critical element in determining whether a water is federally regulated or not. The NWPR’s preamble defines “typical year” as “when precipitation and other climatic variables are within the normal periodic range (e.g., seasonally, annually) for the geographic area of the applicable aquatic resource based on a rolling thirty-year period.” The EPA fact sheet defines it as “the normal periodic range of precipitation and other climactic variables for that waterbody.”
Whether a particular wetland on your project site is federally regulated will sometimes depend upon how the Army will determine if it is inundated in a “Typical year.” Based upon our initial interactions with the Army they appear to be using two methods. First, they appear to be assuming that inundation from the 10-year storm event is equivalent to a typical year inundation. We believe that approach over-estimates the hydrologic connection from a typical year, because a 10-year storm event only has a 10% annual chance of occurring, which is hardly typical. This will tend to add wetlands to federal jurisdiction rather than exclude them.
Second, they are relying on the U.S. Army Corps of Engineers’ Antecedent Precipitation Tool (APT) to determine if a hydrologic connection exists. The ATP obtains 30 years of precipitation data from nearby weather monitoring stations to estimate if the site condition is “wet”, “normal”, or “dry”. The APT defines “normal” as within the 30th and 70th percentiles of the 30 years of precipitation data. While the APT can describe the general condition of a site, it cannot detect if a wetland will be inundated by flooding or connected hydrologically to a WOTUS, so it does not resolve the uncertainty in determining federal jurisdiction. We are not sure how the Army is using this approach to determine jurisdiction.
Both methods are not technically rigorous. If your project requires a drainage study and you are using a hydrology and hydraulics model for design and permitting, we urge you to consider using the model to estimate the maximum water surface elevation resulting from the average depth of rain falling in any 24-hour period observed at a nearby rain gauge during the past 30-years. This meets the regulatory intent of the “typical year.” Your drainage study expert can obtain the 30 years of daily observations from a nearby gauge, calculate the average rainfall depth, and then drop that rain data into the model. The water elevations can be compared to the wetland elevations to determine which are inundated and which are not.
For any questions or more information, please contact Austin Zen, ENV SP, Environmental Scientist, at (281) 921-8720 or at firstname.lastname@example.org.