The U.S. Environmental Protection Agency (EPA) recently published the final report, Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis of the Scientific Evidence.  Its importance relates to Clean Water Act (CWA) jurisdictional decisions over more isolated wetlands and small or seasonal streams. Since the 2006 U.S. Supreme Court decision, Rapanos v. United States, a geographically isolated waterbody (such as a vernal pool or intermittent stream) must have a "significant nexus" to "navigable waters" to be regulated under the CWA; however, the term, "significant nexus," has remained controversial and open to interpretation.

The Connectivity Report investigated over 1,200 peer-reviewed studies regarding the effects of streams, non-tidal wetlands, and open waters on larger downstream waters. Among the findings from the literature are the following:

• All streams with flows connecting to larger, downstream waters affect those receiving waters, regardless of the size of the stream or frequency of flows.  
• Wetlands in the riparian areas and floodplains of rivers protect downstream water quality and are physically, chemically, and biologically integrated with the rivers.
• Disconnected, isolated wetlands may provide physical, chemical, and biological functions that could affect the integrity of downstream navigable waters, such as by intercepting pollutants that would otherwise travel downstream.
• Cumulative conditions of a watershed influence the functions of streams and wetlands and must be evaluated to determine the nexus to downstream waters.

Under CWA Section 404, the EPA and the U.S. Army Corps of Engineers (USACE) have permitting authority regarding discharge of dredged or fill material into “navigable waters of the United States.” Under current guidance, the regulatory agencies assert jurisdiction over traditional navigable waters, wetlands adjacent to traditional navigable waters, non-navigable tributaries of traditional navigable waters that are relatively permanent (i.e., perennial or seasonal), and wetlands that directly abut such tributaries. Jurisdiction over more isolated waterbodies is based on a fact-specific analysis regarding whether they have a significant nexus with a traditional navigable water.   

A significant nexus exists when the tributary and/or wetland has a more than insubstantial effect on the “chemical, physical, and/or biological integrity” of traditional navigable waters. The Connectivity Report provides evidence regarding the chemical, physical, and/or biological functions and effects of wetlands on traditional navigable waters. It is consistent with draft EPA and USACE guidance regarding waters protected under the CWA. The Connectivity Report will be considered in the development of rulemaking regarding CWA jurisdiction and, in the meantime, may assist in making decisions about significant nexus in CWA permit jurisdictional determinations.

If you have any questions, please contact Bonnie Peterson, Ascent's Regulatory Practice Manager, or Ascent Principal, Curtis Alling.