Legal Challenges Could Flow from Tributary Definition

On May 27, the U.S. Environmental Protection Agency (EPA) and the U.S. Army announced the Clean Water Rule, which is intended to clarify the scope of the Clean Water Act in determining jurisdictional waters.

The Clean Water Rule generally maintains the current status of municipal separate storm sewer systems and encourages the use of green infrastructure to protect water quality. However, questions remain about the rule’s definition of tributaries and when that definition applies to ephemeral or intermittent streams — which would make them jurisdictional. According to the EPA, 60% of U.S. stream miles flow only seasonally or after rain, and 1 in 3 Americans rely on these sources for drinking water.

According to some environmental attorneys, the tributary definition is the part of the rule most likely to be challenged. Based on the rule, a tributary must possess the physical characteristics of a bed, bank, and an ordinary high water mark as well as evidence of the frequency, duration, and volume of flow characteristic of a tributary. Further, to be considered jurisdictional, tributaries must significantly affect the health of downstream waters. Based on these definitions, tributaries primarily include headwater streams.

Additionally, there has been ongoing concern about whether ditches fall under the definition of a tributary. Erosional features and ditches with intermittent flow specifically are excluded along with ditches draining into wetlands. According to EPA, the rule limits protections to ditches that involve a relocated tributary or ones that are excavated in a tributary.

The final rule also further defines adjacent open waters and wetlands as jurisdictional if they are within 100 feet of the ordinary high water mark of a jurisdictional water or within the 100-year floodplain and within 1500 feet of the ordinary high water mark of covered waters. Certain isolated waters also could fall under the scope of the Clean Water Act based on both their connectivity and proximity to traditional navigable waters, interstate waters, and territorial seas. A significant nexus determination is based on the isolated water’s effects on the physical, biological, or chemical integrity of jurisdictional waters, such as through an exchange of pollutants, flow, or organisms. Additionally, scientific analyses assessing connectivity will consider how isolated waters affect the nearest jurisdictional water as a group rather than individually.

Under the Clean Water Rule, an exclusion will trump an inclusion, said Ken Kopocis, deputy assistant administrator of EPA’s Office of Water, in a recent webcast about the rule. So even if an excluded ditch falls within the defined limits of adjacent waters, it will not be considered jurisdictional. Read more.

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