In what is keying up to be a very controversial issue, the EPA and Corps issued a new rule on May 27, 2015 defining “waters of the United States”. The agencies intend the new definition to be a “bright line” for delineating the limit of their jurisdiction under the Clean Water Act (CWA). This new Rule affects all aspects of the CWA, including the regulation of discharges into waters of the United States, as well as the National Pollutant Discharge Elimination System permit program, the oil spill prevention and response program, and the water quality and total maximum daily load programs. The agencies suggest that their bright line is “narrower than under existing regulation,” but the basis for such a statement may be hard to find in the new Rule. The new definition will have implications to future projects in determining impacts to “waters of the U.S.”, will affect permitting strategies, and may also have an effect on state wetland programs currently under consideration.
Wetlands and open waters (e.g. rivers, streams, and ponds) are both included in the definition, some of which will be regulated “by rule” and others for which a significant nexus determination will be required. A few will not be covered due to their greater distance from a regulated tributary and a number of aquatic features will be exempted by definition.
Regulated by inclusion in the definition
The new definition expands regulation to all “tributaries to traditional navigable waters” that possess an ordinary high water mark, including wetlands and non-wetland waters (e.g., lakes and ponds) that are within 1,500 feet of a regulated tributary or tidal water. This is a significant expansion of the definition as previously some tributaries were not regulated if they did not have a significant nexus or may have flowed underground prior to reaching a navigable water.
Supporting the inclusion of all tributaries under the new Rule, the agencies state that the science, as summarized in the EPA’s technical report  concerning the ecological and physical connectivity of tributaries, has met the burden created by the Rapanos decision to show a significant nexus regardless of the duration or magnitude of their flow. The basic definition of a tributary is any linear drainage feature that possesses an “ordinary high water mark” (OHWM). The features used to demarcate the upper limit of the OHWM, can be readily discerned in the field using guidance developed by the Corps in recent years. Most of the features used to identify the OHWM are left by flowing water and can occur equally in natural tributaries and in man-made drainages, making it important to distinguish between those features which meet the limited exclusions as non-regulated ditches dug in uplands and those which regulated because they are re-aligned tributaries. In addition, the agencies have determined that a tributary does not lose its jurisdictional status even if it flows underground or through culverts, concrete channels, or pipes for any distance before being discharged to another tributary.
Redefining the terms used to evaluate adjacency, wetlands and non-wetland waters will now be considered jurisdictional if they are located either within the 100-year flood plain or within 1,500 feet of a tributary or tidal water whichever is smaller. This “brightline” is larger than what has been used in the past by many Districts in establishing adjacency and is based on a new definition of the term “neighboring”.
Regulated if a significant nexus is present
 assuming they are not within five categories that include prairie potholes, Carolina and Delmarva bays, pocosins, western vernal pools, and Texas coastal prairie wetlands. Wetlands that fit within any of these categories must be evaluated in a combined manner when it comes to a significant nexus test and most likely will always be subject to federal jurisdiction regardless of their distance or hydrologic connection to traditional navigable waters.
Two aspects of the significant nexus determination make it likely that many, if not all, wetlands will be regulated. The first is that wetlands will be consolidated as “similarly situated” and the significant nexus will be evaluated based on the functions of all similar wetlands in the watershed, with the assumption that when evaluated as a whole rather than individually there may be a noticeable effect on downstream navigable waters. The definition of “similarly situated” wetlands includes all wetlands within a watershed that drain to the nearest navigable water. The larger the watershed, the more “similarly situated” wetlands there are and the agencies have used a large watershed size based on flow to the nearest navigable water. As a result, wetlands draining into tributaries that may only reach a navigable water many miles downstream will be combined and evaluated under the significant nexus guidelines. Secondly, the new Rule provides for many factors to be evaluated for significant nexus and that the presence of any one factor may be used to reach a significant nexus determination. One of these factors is “contribution of flow” and another is “runoff storage,” factors which are both likely to be attributed to most wetlands. Some of the factors are so vague or difficult to disprove that applicants will face an uphill battle in overcoming the assumption that a significant nexus does exist. Given the applicability of these factors to most wetlands and the consideration of all wetlands within the watershed when making the determination, it is likely that all wetlands will be found to have a significant nexus and will therefore be covered under the definition.
May not be regulated due to distance from a tributary
The definition excludes those wetlands that are outside the 100 year floodplain or more than ¾ of a mile from the nearest tributary or tidal wetland. As noted above, some categories of wetlands that may fit into this group will be regulated regardless of their distance. However, given the high density of tributaries in many landscapes and the practical implications that two adjacent tributaries with their individual combined buffer distances will total 1.5 miles, it is not likely, except in very flat landscapes, that any wetland will be truly outside the required distance.
Ditches have been given considerable attention in the new definition, with ephemeral ditches excluded as long as they do not contain a “relocated tributary,” or are excavated in a tributary. Using slightly different criteria, intermittent ditches are excluded as long as they do not contain a relocated tributary or drain a wetland. Ditches with a permanent flow are regulated as tributaries.
The agencies continued all previous exemptions and added a few new exemptions for farm ponds excavated in dry land (and not impoundments), log cleaning ponds, and cooling ponds, but admitted that they had been excluded previously by practice. Luckily for those constructing stormwater treatment wetlands, such features have now been exempted, although the agencies claimed that they were never regulated in the past. Finally, puddles have now been officially defined as “a very small, shallow, and highly transitory pool of water that forms on pavement or uplands during and after a rainstorm” and have been exempted from regulation.
Implications to landowners and permit applicants
The new Rule is intended to take effect within 60 days following its publication in the Federal Register, which is scheduled for late June 2015 (with the new Rule taking effect in late August 2015). However, it is likely that Congress will continue to hold hearings, pass legislation, withhold funds, or find other mechanisms for delay. Whether they are successful will depend upon the necessary votes to override a Presidential veto. Various industry and agricultural interests are also likely to sue and seek an injunction. However, it is best to expect that these new definitions will remain in effect until some future Supreme Court overturns the new Rule or further redefines “waters of the U.S.” Under that scenario, landowners and public agencies seeking to undertake projects should recheck their calculations on impacts and mitigation based on the new definition for projects that are not yet in the pipeline. Luckily, a grandfathering provision is in effect with the new Rule if you have an approved or preliminary JD already.
The “bright line” is likely to become more obscured as various groups read the fine print and as the agencies develop guidance for their staff to implement these definitions. Interpretations are likely to vary considerably so the best approach is to consult with both your biologist and your legal counsel as this new definition takes hold.
 Significant nexus is a term proposed by Supreme Court Justice Kennedy as a basis for evaluating whether a wetland has an important enough influence on navigable waters to be regulated under the Clean Water Act.
 US EPA. 2015. Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis of the Scientific Literature.
 As a practical matter, the density of tributaries on the landscape is such that few wetlands would be found more than 4000 feet from a regulated tributary; however, in flat landscapes it may be possible.
 This was recognized as a potential problem in the Arid West because of the relatively large watersheds draining to a feature that is defined as a navigable water and an exception was added that it may be more reasonable to use a smaller watershed such as a HUC 10 hydrologic unit.