[US] Final Rule: Rulemaking Clarifies Definition of “Waters of the U.S.” Under Clean Water Act

On May 27, 2015, the U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers finalized a rule that clarifies the Clean Water Act’s definition of “Waters of the U.S.”, clarifying the scope of which bodies of water receive protection under the Act.  Although the rulemaking does not impose additional requirements under the CWA, it redefines the scope of waterbodies subject to regulation, including tributaries, seasonal streams, and adjacent bodies of water.

Why clarifying the Clean Water Act Regulations definition of “Waters of the U.S.” ?

In an attempt to clarify which water sources are protected under the CWA, the EPA and the Army Corps of Engineers have finalized a rule (the “Waters of the U.S. Rule”) that expands on the definitions of which waterbodies are subject to regulation under the Act.  The rule refines the definition of “tributary” and clarifies what kinds of wetlands, erosional features, and ditches are covered under the Waters of the U.S. Rule.  The rule specifies that tributaries (which feed downstream waters), “must show physical features of flowing water—a bed, bank, and ordinary high water mark—to warrant protection.”  This is significant because the rule establishes that wetlands, lakes, and ponds can be tributaries if they contribute to downstream flow, and therefore would be subject to the permitting requirements under the CWA.

Establishing for the first time a boundary limit on what constitutes an “adjacent body of water”

In addition, the Waters of the U.S. Rule establishes a boundary limit on what constitutes an “adjacent body of water” for the first time in CWA history.  Specifically, an adjacent body of water is protected if it is within the 100-year flood plain (an area that has a 1 percent chance of flooding each year) but is not more than 1,500 feet from a protected waterbody.  Furthermore, certain water features such as prairie potholes, Texas coastal prairie wetlands, and western vernal pools in California are now explicitly afforded CWA protection.  Planting, harvesting, and moving livestock activities will continue to be exempt under this rule, and new exemptions for certain artificial lakes and ponds have been enacted.

No creation of new permitting requirements

Although the rule does not create any new permitting requirements, it also does not address land use or private property rights.  Since the EPA and Army Corps of Engineers proposed it in April 2014, the new rule has faced opposition from farmer coalitions, oil and gas stakeholders, and other industries that disparage it as an overstep of federal authority.  Since ditches that function like a tributary will now be regulated under the rule, agricultural opponents criticize the rule as a federal land grab that should be overturned.  The House has already passed legislation (H.R. 1732, the Regulatory Integrity Protection Act of 2015) to block the rule and legislation that would require the EPA to change the rule is now being considered in the Senate (S. 1140, the Federal Water Quality Protection Act).

The new Waters of the U.S. rule will become effective 60 days after it is published in the Federal Register.

Red-on-line EHS Legal specialist

Sources :


H.R. 1732, the Regulatory Integrity Protection Act of 2015 


Clean Water Act

Proposed Rule Amending Definition of “Waters of the United States” Under the Clean Water Act, Federal Register, 79 FR 22187 (April 21, 2014) 

Solid Waste Agency of Northern Cook County v. Army Corps of Engineers, 531 U.S. 159 (2001)