Final Clean Water Act Rulemaking: What is a Water of the United States?

Final Rule Issued:  On May 26, 2015, the Environmental Protection Agency (“EPA”) and the U.S. Army Corps of Engineers (“Corps”) issued their final rule defining the scope of “waters of the United States” regulated under the Clean Water Act (“CWA”).1 The agencies assert the rule will simplify and speed up the permit process through clearer definitions and increased use of bright-line boundaries to establish features that are “jurisdictional by rule” and therefore do not require case-specific analyses of a significant nexus to a downstream water of the United States to establish jurisdiction.

The attached charts itemize the types of features that are included in the definition of waters of the United States, and those that are expressly excluded from the definition in the new rule.

Many comments on the draft rulemaking were generally unfavorable, asserting that the agencies are engaged in a vast expansion of federal power and that the rule would more than double the miles of waterway subject to regulation under the CWA.  Resource companies, agricultural interests, the construction industry, and developers are concerned about regulatory impacts, particularly in the Southwest where dry conditions already make jurisdictional determinations difficult.  Further, expanding jurisdiction over small and headwater channels could substantially expand the areas of typically dry features subject to regulation.

Why It Matters:  The scope of waters of the United States is important because the CWA imposes significant regulatory requirements on private activities. Section 404 requires Corps permits for placement of “fill” material into waters of the United States. Section 311 mandates provisions for oil spill prevention and response.  Section 402 imposes requirements for point source discharges, and section 401 requires state or tribal water quality certifications. Issuance of a CWA permit is a federal action that triggers the requirements of the National Environmental Policy Act and other federal statutes, including the Endangered Species Act and the National Historic Preservation Act.  A determination that an activity triggers regulatory jurisdiction under the CWA can result in significant delays and expense.

What are Waters of the United States?:  The CWA provides the Corps and EPA authority to regulate activities in “Navigable Waters,” which include “Waters of the United States, including the territorial seas.”2 Such waters do not have to be “navigable in fact,” but must have a connection to interstate or foreign commerce.3 The agencies defined waters of the United States to include features such as rivers and lakes that are considered “traditionally navigable waters,” as well as interstate waters including wetlands, impoundments of waters of the United States, tributaries of waters of the United States, adjacent wetlands, and some intrastate waters with interstate commerce connections.4

The definition of this term and the extent of regulatory jurisdiction have been contentious.  Recent United States Supreme Court decisions excluded isolated intrastate waters from CWA jurisdiction, and led to a requirement to establish a “significant nexus” with a downstream water of the United States “more readily understood as navigable” in order to exert jurisdiction over upstream tributaries on a case-by-case basis.5 The agencies have repeatedly attempted to provide clarity to the regulated community following court decisions, and this rulemaking is the latest and most comprehensive effort.

Key Changes in the New Rule:

Jurisdictional by Rule:  Under the previous rules and practice, the agencies made case-by-case jurisdictional determinations, and compiled site-specific evidence to make “significant nexus” determinations.  The new definition eliminates the need for case-by-case determinations for many types of features that are now defined as “jurisdictional by rule” without site-specific confirmation.  In particular, all tributaries of waters otherwise identified as Waters of the United States are jurisdictional by rule, and will not require a case-specific analysis to establish existence of a significant nexus in order to exert jurisdiction.

Tributaries: Tributaries can include natural or man-altered waters, including some ditches, and can extend upstream to small “headwater” channels. The new rule makes a categorical finding of significant nexus for all tributaries, including headwaters far upstream from any “traditionally navigable water,” regardless of whether or how often water actually flows from the headwaters to the downstream navigable water.  This conclusion relies on scientific studies that accompany the rulemaking and are available on EPA’s website.

Erosional Features: The rule clarifies that small erosional features such as rills and gullies are not jurisdictional waters of the United States.  The final rule explains that the difference between these features and tributaries is that tributaries exhibit a bed, banks and an ordinary high water mark, and erosional features do not.  However, since tributaries are now “jurisdictional by rule” and no further analysis is required, it is unclear how the agencies will define the upstream limits of tributaries, particularly in the arid Southwest, without case-specific analyses.

Ditches: Certain ditches are now expressly excluded from jurisdiction, including ditches with ephemeral or intermittent flow that are not a relocated tributary or excavated in a tributary, or that drain wetlands.  Also excluded are ditches that do not flow, either directly or indirectly, into a water identified in paragraphs (i) through (iii) (those waters more readily understood as navigable).  Roadside ditches are not expressly excluded, but the preamble notes that many such ditches will be excluded under the new definition.  It appears that ditches that drain to a tributary (but do not relocate a tributary and are not excavated in a tributary), or drain to an impoundment, adjacent water, or other water would not be jurisdictional.  Further, the rule does not affect the exemptions under CWA § 404(f) for irrigation ditches and maintenance of drainage ditches.

Nearby and Neighboring Waters: The rule now provides bright-line distances for jurisdiction over nearby waters in category (viii), and to establish “neighboring” waters for purposes of “adjacency.”

Other Exclusions:  The rule retains the existing exclusions from jurisdiction, including water treatment systems, prior converted cropland, artificial features, and groundwater, and adds exclusions the agencies historically applied in practice.

Connectivity: While the preamble notes that groundwater and other excluded features are not waters of the United States, it reiterates that such features can be used to establish connectivity between upstream and downstream features which themselves may be waters of the United States due to that connection.

Take-Aways:  The new rule could have serious implications for private activities that affect waterways, channels, and wetlands.  In the arid Southwest, upstream channels and arroyos can be dry most of the time and carry water only sporadically after intense precipitation events, and then only for short distances.  The application of the “jurisdictional by rule” definition will result in all tributaries being subject to regulation, regardless of whether case-specific evidence of a significant nexus to a downstream water of the United States exists to justify that conclusion in particular circumstances.  Further, it remains unclear how far upstream a tributary designation will extend.  That can be a particularly complex determination in arid Southwest channels.  While the agencies assert the new definition should speed up the Corps’ permit process since it will not require site-specific evidence to establish a significant nexus for features now considered “jurisdictional by rule,” site work will likely still be necessary to determine the boundary between jurisdictional (bed, bank and ordinary high water mark) and non-jurisdictional features, and to assess efficacy of proposed mitigation measures.


  1. 1.  The pre-publication version and additional information about the final rule are available here.
  2. 2.  33 U.S.C. § 1362(7).
  3. 3.  The waters must be presently used, used in the past, or may be susceptible for use (with or without reasonable improvements) to transport interstate or foreign commerce.  33 C.F.R. Part 329.
  4. 4.  33 C.F.R. § 328.3; 40 C.F.R. § 230.2.
  5. 5.  See Solid Waste Agency of N. Cook Cnty. v. U.S. Army Corps of Eng’rs, 531 U.S. 159 (2001); Rapanos v. United States, 547 U.S. 715, 780 (2006).  The waters identified in paragraphs (i) through (iii) of the rule (e.g., waters used in interstate or foreign commerce, interstate waters, and the territorial sea), and those with perennial or regular flow sufficient to float a boat, are typically seen as “more readily understood as navigable.”