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Regulatory Updates

Interpretation of “Waters of the United States” (WOTUS) Reverts to Pre-2015 Regulatory Definition

Sherry Constable | September 29, 2021

On August 31, 2021, the U.S. District Court for the District of Arizona issued an order vacating and remanding the 2020 Navigable Waters Protection Rule in the case of Pascua Yaqui Tribe v. U.S. Environmental Protection Agency. Based on this order, the United States (U.S.) Environmental Protection Agency (EPA) and U.S. Army Corps of Engineers (ACOE) have halted implementation of the 2020 Navigable Waters Protection Rule and are interpreting the definition of “waters of the United States” (WOTUS) consistent with the pre-2015 regulatory program. The U.S. EPA and U.S. ACOE (the agencies) have indicated that they will continue to review the order and consider next steps, including moving forward with revising regulations as announced on June 9, 2021.

Hence, at this time and until further notice, the U.S. EPA and U.S. ACOE will interpret the term “waters of the United States” to mean the pre-2015 regulatory definition as included in Title 40 Code of Federal Regulations Section 230.3(s) (40 CFR 230.3(s):

  1. All waters which are currently used, or were used in the past, or may be susceptible to use in interstate or foreign commerce, including all waters which are subject to the ebb and flow of the tide;
  2. All interstate waters including interstate wetlands;
  3. All other waters such as intrastate lakes, rivers, streams (including intermittent streams), mudflats, sandflats, wetlands, sloughs, prairie potholes, wet meadows, playa lakes, or natural ponds, the use, degradation or destruction of which could affect interstate or foreign commerce including any such waters:
    1. Which are or could be used by interstate or foreign travelers for recreational or other purposes; or
    2. From which fish or shellfish are or could be taken and sold in interstate or foreign commerce; or
    3. Which are used or could be used for industrial purposes by industries in interstate commerce;
  4. All impoundments of waters otherwise defined as waters of the United States under this definition;
  5. Tributaries of waters identified in paragraphs (s)(1) through (4) of this section;
  6. The territorial sea;
  7. Wetlands adjacent to waters (other than waters that are themselves wetlands) identified in paragraphs (s)(1) through (6) of this section; and,
  8. Waste treatment systems, including treatment ponds or lagoons designed to meet the requirements of CWA (other than cooling ponds as defined in 40 CFR 423.11(m) which also meet the criteria of this definition) are not waters of the United States. [, September 13, 2021]

To ensure you are compliant with this regulatory change, we recommend you review and consider the following:

  • If you have a permit, certification, or permit application under review that is affected by the WOTUS interpretation, TRC recommends discussing the implication of the recent U.S. EPA and U.S. ACOE position with your regulating entity to determine if any changes to the permit, certification, or permit application are needed.
  • If you have WOTUS that have the potential to change status from the 2020 Navigable Waters Protection Rule definition to the pre-2015 interpretation, TRC recommends re-evaluating the applicability of WOTUS to the site and identifying affected permits and certifications.
  • If your facility is not currently subject to Clean Water Act programs because there are not WOTUS at the site, TRC recommends evaluating whether the new WOTUS interpretation will trigger Clean Water Act permitting and compliance requirements and consult with your regulating entity.
  • The U.S. EPA and U.S. ACOE are planning further revisions to the regulations. Stay abreast of additional future changes to the WOTUS definition interpretation.

TRC will continue to monitor and provide updates on this regulation. You can contact for more information.

Sherry Constable

Sherry is TRC’s National Service Leader for Hazardous Materials/Hazardous Waste Services. She has 25 years of experience in environmental engineering and consulting with oil and gas; industrial; and government clients and specializes in solid and hazardous waste management; spill and emergency response planning and preparation; regulatory analysis; RCRA permitting; stormwater management and permitting; and facility compliance. She holds a bachelor’s degree in Environmental Engineering from Vanderbilt University and a master’s degree in Civil/ Environmental Engineering from the University of Texas at Austin. Sherry can be reached at

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