The Science Advisory Board has at last released its peer review of EPA’s draft report on Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis, the technical support for the proposed rule on definition of “waters of the United States” under the Clean Water Act. The SAB paper is generally supportive of EPA’s analysis.

As has been reported in this blog, the proposed rule has generated a great deal of controversy, causing EPA and the Corps to extend the comment period twice (November 14 is the current deadline). Part of the controversy relates to EPA’s analysis of the technical literature supporting the proposed rule, particularly the effect of tributaries, intermittent and ephemeral streams on navigable waters. A detailed explanation of the proposed rule, case law leading up to it, and prior agency guidance can be found here.

The SAB paper confirms EPA’s science, but recommends more nuance in some instances. For example, the paper agrees that tributaries, intermittent and ephemeral streams can have a significant effect on the physical, biological and chemical integrity of receiving waters, but notes that the question is not simply whether there is a connection between upstream sources and navigable waters. Rather, the paper urges EPA to acknowledge there is a “gradient of connectivity.”

The SAB also makes recommendations to improve the clarity of the EPA report and make more definitive statements. For example, the SAB states that the literature supports a firmer statement on downstream functions of “unidirectional,” non-floodplain wetlands. The SAB also recommended that EPA expand the discussion of approaches to quantifying connectivity, which would increase the utility of the document for regulators.

The SAB paper certainly is a necessary element of the scientific support for EPA’s and the Corps’ proposed rule for determining jurisdiction. But it is unfortunate that the agencies reached their policy choices in the proposed rule without the benefit of the SAB’s input.

Whether that reversed sequence matters in the long term remains to be seen. Even if EPA and the Corps had waited until the SAB completed its peer review, the rule would probably have come out roughly the same and attracted as much comment.