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Streamflow duration assessment method now available

Release Date: 03/06/2009
Contact Information: Scott Clemans (Corps), 503-808-4510; Tracie Nadeau (EPA), 503-326-3685; Jess Jordan (DSL), 541-388-6060

Tool designed to help identify waters subject to regulatory jurisdiction
PORTLAND, Ore. — The U.S. Army Corps of Engineers, U.S. Environmental Protection Agency and Oregon Department of State Lands today made available a new tool to help identify waters that may be subject to those agencies’ regulatory jurisdiction.
The Oregon Streamflow Duration Assessment Method is a scientific tool for quickly analyzing more than 20 environmental factors to distinguish between ephemeral, intermittent and perennial streams.
That data will be used to determine whether a stream may be subject to jurisdiction under Section 404 of the Clean Water Act and the State of Oregon’s Removal-Fill statute.
Conducting work that impacts such streams, such as placing fill in them to prepare a site for future construction, often requires a permit from the Corps’ Regulatory Branch and DSL’s Removal-Fill Permit Division.
 “Teams of scientists have field-tested the method to assess its clarity and ease of use,” said Richard Parkin, director of EPA’s Office of Ecosystems, Tribal and Public Affairs in Seattle.  “We believe this method is a major step in evaluating streams and ensuring environmental protection of our water resources.”
Use of the method is recommended but not required, said Mike Turaski of the Corps’ Regulatory Branch. “We encourage regulators, consultants and natural resource specialists to use the method, because it will make it easier to provide the information the Corps and DSL need to make more timely and predictable jurisdictional determinations,” he said.
The agencies have released the method for use as an interim version.  It will be tested for one year before it is finalized, and the agencies encourage practitioners and the public to provide comments on their experience using it.
The agencies will hold training sessions in Portland, Medford and LaGrande, Ore., this spring to help interested parties become more familiar with the method.
Information about the method, data forms and training sessions will be available on the Web at
For more information about the Corps’ Regulatory program or DSL’s Removal-Fill Permit program in Oregon, visit or
Information about the EPA’s Pacific Northwest Regional Office is available at