October 31, 2014

Definition of "Waters of the United States" Under the Clean Water Act

  • Ryan M. Yonk

  • Ken J. Sim

  • Josh DeFriez

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The Environmental Protection Agency and Army Corps of Engineers have proposed a rule changing the definition of “waters of the United States” under the Clean Water Act (CWA). Under current law, whether or not a water body qualifies as “waters of the United States” is determined case-by-case. The proposed rule seeks to add clarity to this process by providing a more robust definition for “waters of the United States.”

The rule would lead to expansion of the agencies’ jurisdiction, and it would impose higher costs on those who comply with the CWA. The proposed rule fails to demonstrate that its benefits outweigh its costs. It will likely fail to improve environmental outcomes and lead to uncertainty about what is allowed under the CWA.

Alongside this regulation, the EPA and US Department of the Army issued an interpretive rule related to exemption from permitting under the Clean Water Act. Significant regulatory actions, as defined under President Clinton’s Executive Order 12866, must undergo review by the Office of Information and Regulatory Affairs (OIRA) and often must also be accompanied by a Regulatory Impact Analysis. Interpretive rules can have significant economic impacts, just as regulations do, and agencies that employ these methods can circumvent procedures in the regulatory process put in place to ensure sound decision-making. 


  • The proposed rule increases areas of uncertainty for those that must comply with the CWA. For example, the proposed definition of “tributary” is so broad that a home’s rain gutter could very well qualify and be deemed jurisdictional by the agencies.
  • The agencies have underestimated or failed to accurately describe their proposed increase in jurisdiction. The rule empowers the agencies to establish jurisdiction over virtually any water formation nationwide.
  • The agencies have failed to analyze the costs of delayed and forgone development. For example, on a recent small project under CWA jurisdiction, compliance cost an estimated additional 3.5 years of delay and over $2.5 million in direct costs.
  • The agencies have failed to adequately analyze the costs to local governments. Cities in floodplains or with streams and rivers will have to spend time and money to prove to the agencies that they are not affecting jurisdictional waters.
  • The definitions in the proposed rule use a one-size-fits-all approach that ignores the variety of environmental and economic realities across the nation. For example, 94 percent of Arizona’s and 88 percent of New Mexico’s waterways are intermittent or ephemeral in nature, and thus the proposed rule could disproportionately affect development in the Desert Southwest.
  • The scientific report upon which the agencies have based the rule has not yet been peer-reviewed or released for public scrutiny.


  • The EPA and Army Corps of Engineers should recognize legal limits required by Supreme Court precedent.
  • The agencies should also disclose and peer-review the science on which the proposed rule relies.
  • Along with this regulation, the agencies issued an interpretive rule regarding the applicability of the exemption from permitting under the Clean Water Act. The agencies should comply with Executive Order 12866, which requires that significant regulatory actions undergo review by the Office of Information and Regulatory Affairs within the Office of Management and Budget. 
    Along with this regulation, the agencies issued an interpretive rule regarding the applicability of the exemption from 
    permitting under the Clean Water Act.