August 29, 2022

Defining the “Waters of the United States” is a Twisting Tributary of Change


The “Waters of the United States” (WOTUS) seems simple enough to define. Yet the definition of WOTUS has expanded and contracted at least three times in the past seven years alone, with each new administration putting a new tributary-like twist on it.

It is important to know what bodies of water are considered WOTUS because it dictates whether the federal Clean Water Act applies to that body of water. The Clean Water Act prohibits discharge of pollutants from a point source into WOTUS without a permit under Section 402. The Army Corps of Engineers has the authority to issue permits for the discharge of dredge and fill material into WOTUS under Section 404. Under Section 303, the states and tribes must adopt water quality criteria for WOTUS, and establish total maximum daily loads of pollutants for WOTUS that does not meet the criteria.

The definition of WOTUS has been in flux for many years between regulatory rulemaking and Supreme Court rulings that have provided less than helpful guidance.

How is WOTUS currently defined? The list includes waters used for interstate commerce; interstate waters including interstate wetlands; other waters whose degradation or destruction could affect interstate or foreign commerce; impoundments of waters otherwise defined as waters of the United States under this definition; certain tributaries of waters; the territorial sea; and wetlands adjacent to these waters.

What’s not a WOTUS? Ephemeral features that flow only in direct response to precipitation and diffuse stormwater runoff; ditches; prior converted cropland; artificially irrigated waters; artificial lakes; water-filled depressions constructed or excavated incidental to mining or construction activity; and water-filled pits excavated for the purpose of obtaining fill, sand or gravel. While groundwater and groundwater connections have generally not been viewed as a WOTUS, the Supreme Court in County of Maui, Hawaii v. Hawaii Wildlife Fund et. al. held that the Clean Water Act requires a permit if the addition of pollutants through groundwater is the functional equivalent of a direct discharge to WOTUS.

Any waters that are not WOTUS can still be regulated by state law, which can be more stringent. In Washington, the water quality standards prescribed by state law are applied to non-WOTUS wetlands. Oregon has broad state authority to regulate and protect surface waters, and stream and wetland protection are carried out through permitting programs such as Oregon’s Removal-Fill Law.

The constant flux of the definition hinges on each administration’s take on WOTUS. In 2015, the Obama administration’s Clean Water Rule attempted to define WOTUS extremely expansively, to include even minor isolated streams and wetlands, requiring only a “significant nexus” between those waters and larger “navigable waters.” The Trump administration repealed the Obama-era rule with the Navigable Waters Protection rule, eliminating the significant nexus test, and limiting WOTUS to navigable waters, their tributaries, lakes, ponds and impoundments of navigable waters and adjacent wetlands.

The Trump-era definition of WOTUS was challenged by 20 states in a lawsuit, including Oregon. In 2021, the US. District Court of the District of Arizona vacated and remanded the Navigable Waters Protection rule. After that, the EPA announced a proposed rule to revise the definition to put the pre-2015 definition back into place with updates to respond to Supreme Court decisions. The Supreme Court recently accepted a case interpreting WOTUS (Sackett v. Env’t Protection Agency), with oral arguments expected in October.

Meanwhile, the Biden administration seeks to expand the definition once again. If recent history is any lesson, we can expect each new Republican administration to attempt to reduce the reach of the Clean Water Act, and each new Democratic administration to seek to increase the reach. For industries discharging pollutants or stormwater and those involved in dredge and fill projects, keeping a close watch on this issue is essential to ensuring compliance with the Clean Water Act.

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Tags: Water, Environmental and Natural Resources

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