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On June 22, 2020, the Navigable Waters Protection Rule (NWPR) became effective in all states, except Colorado. Under the new rule, waters of the U.S. (WOTUS) are defined as:

  1. territorial seas and traditional navigable waters (TNWs)
  2. perennial and intermittent tributaries that contribute surface water flow to Category 1 waters in a typical year
  3. certain lakes, ponds, and impoundments of jurisdictional waters
  4. wetlands adjacent to other jurisdictional waters

The NWPR also defines 12 categories of exclusions. Most notably, all ephemeral streams (e.g., arroyos) are categorically excluded from being considered a WOTUS and therefore are not federally protected under the Clean Water Act (CWA). Federal CWA Section 404 permits for dredge or fill activities would not be necessary for impacts to such drainage features.

New Arizona Regulations

In Arizona, the Arizona Department of Environmental Quality (ADEQ) administers a number of CWA programs, includingSection 402 of the CWA, known as the Arizona Pollution Discharge Elimination System (AZPDES). In response to the new federal rule, ADEQ is currently pursuing changes to the definition of “Waters of Arizona” (WOA) and associated state regulations, including the AZPDES permit program, that would apply to certain categories of surface water features that are not protected under the CWA NWPR.

Once the new WOA changes are in place, projects that do not discharge directly to a WOTUS as defined under the NWPR (either directly or indirectly via a local Municipal Separate Storm Sewer System [MS4]) may still require an AZPDES permit and Stormwater Pollution Prevention Plan (SWPPP) if located on non-tribal land, cause 1 acre or more of ground disturbance, and may discharge to a WOA.

More information is provided here:


With offices across the U.S., including three in Arizona, SWCA can provide coordination services and local assistance in complying with the Clean Water Act. Please contact rwaldron [at] swca [dot] com (Russell Waldron) or victoria [dot] casteel [at] swca [dot] com (Vicki Casteel) for more information.