The Trump administration last week scaled back Clean Water Act (CWA) protection of wetlands by narrowing the definition of waters falling under the U.S. Environmental Protection Agency’s (EPA’s) oversight. A new EPA Final Rule announced on January 23 replaces an Obama administration policy rescinded by the Trump administration in September that had employed a broader definition and thus placed more wetlands under federal regulation.

The new Rule, known as the Navigable Waters Protection Rule, sets forth four categories of waters protected under the CWA: (1) territorial seas and traditional navigable waters; (2) perennial and intermittent tributaries; (3) certain lakes, ponds and impoundments (those that “contribute surface water flow in a typical year” to territorial seas/traditional navigable waters); and (4) wetlands that are adjacent to those jurisdictional waters. The Rule protects navigable waters and core tributary systems flowing into those navigable waters, according to the EPA’s press release. The Rule also expressly identifies waters that will not be subject to CWA jurisdiction. These include areas that contain water only in direct response to rainfall, groundwater, many ditches (including farm and roadside ditches), prior converted cropland, farm and stock watering ponds, and wastewater treatment systems.

The EPA stated that its implementation of the Rule will lead to a unified regulatory scheme and end the robust litigation and resulting uncertainty of the Obama-era policy. It is certain that Trump’s Rule will be challenged, however, and many environmental groups have already stated their intent to do so. They allege the new Rule ignores science and will result in pollution of the nation’s waters by removing federal oversight of many previously regulated waters, including smaller seasonal streams and wetlands that are not adjacent to or specifically connected at the surface to larger navigable waters.