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Wetland Delineation

Wetland delineation establishes the existence (location) and physical limits (size) of a wetland for the purposes of federal, state, and local regulations.

Wetland delineation is also an element of a “jurisdictional determination.” This process identifies which water bodies within a project's boundaries meet the definition of "waters of the United States." For more information on this, see the Corps' Regulatory Guidance Letter 08-02, Jurisdictional Determinations (issued June 26, 2008, PDF 118 kb).

Remember that the Corps of Engineers (Corps), not applicants or their consultants, determines whether or not a wetland is a "water of the United States" and thus regulated under the federal Clean Water Act (CWA). If the Corps determines that a wetland is not subject to the CWA, the wetland may still be a "water of the State" and subject to regulation by Ecology as well as by local jurisdictions. For more information on Ecology's regulation of wetlands determined by the Corps to be non-jurisdictional due to their isolation from navigable waters, click here.

Wetland delineation should result in three things:

A wetland boundary clearly marked in the field.
A map that clearly identifies data collection points and the boundaries of the delineated wetland. (Topographic and aerial site maps are very helpful.)
A report that explains how the boundary was determined. It should include:

A description of how and when the delineation was done.

Data forms used to delineate the wetland area (see shaded box for clarification on which forms to use).

The map described in #2 above.

A soil survey map.

Click here for a checklist of information that should be in your wetland delineation report, as well as a sample report outline.

NOTE: You may need to hire a qualified wetland professional to help you identify and delineate wetlands (using the manuals listed below) and prepare a delineation report. For tips to help you find and select a qualified wetland professional, click here (PDF, 81 KB).

Wetland delineations must be done using the methods outlined in the following manuals:

Washington State Wetland Identification and Delineation Manual (Chapter 173.22.080 WAC). The state manual is consistent with the Corps 1987 manual (described below). It also includes guidance that clarifies the 1987 manual, as well as guidance on regional issues addressed by the Seattle District of the Corps and EPA Region 10. All state agencies require that you follow the state manual for any project that is subject to state laws and regulations on wetlands. Any city or county implementing their regulations under the Growth Management Act (Chapter 36.70A.175 RCW) also requires that you follow it.
1987 Corps of Engineers Wetlands Delineation Manual (PDF, 1.43 MB) and all applicable guidance that is not superseded by the new regional Supplements (see below).
Regional Supplements to the 1987 Wetland Delineation Manual. The Corps is engaged in an ongoing effort to develop supplemental regional criteria for the 1987 Wetland Delineation Manual. Two regions fall within Washington: the Arid West (dry lands west of the Continental Divide, from Idaho and eastern Washington south to the U.S.-Mexico border) and Western Mountains, Valleys, and Coast. For a map of the regions, click here (PDF, 1.5 MB).
The Corps now requires you to use the appropriate regional Supplement when delineating wetlands:
- Arid West Final Regional Supplement (September 2008, PDF, 4.7 MB).
  This is Version 2.0 of the Arid West Regional Supplement; it replaces the “interim” version (PDF, 13MB), which was published in December 2006.
- Western Mountains, Valleys, and Coast Interim Regional Supplement (April 2008, PDF, 5 MB).
  Effective date: June 27, 2008. For details see the Corps Special Public Notice (issued May 28, 2008, PDF, 111 KB).
You can find answers to frequently asked questions about the regional Supplements in the shaded box below.

Frequently Asked Questions:
Regional Supplements to the 1987 Corps Wetland Delineation Manual

Which data forms should I submit to Ecology?

Ecology will follow the same policy as the Corps of Engineers. That is, you only need to submit the data forms found in the appropriate regional Supplement:

Arid West data forms.

Western Mountains, Valleys, and Coast data forms.

However, if you find that using the Supplement results in a different wetland boundary line, we encourage you to submit forms from both the state delineation manual and the Supplement. Ecology will make the final determination on the boundary.

Which data forms should I submit locally?

It depends on your jurisdiction. Some local jurisdictions specifically mention the state delineation manual in their Critical Areas Ordinances. These jurisdictions may require you to use the data forms in the state delineation manual in addition to the Supplement's data forms. Other local jurisdictions might develop a similar policy to Ecology's to simplify the tasks for wetland delineators. That decision, however, will be made at the local level.

Will Ecology revise the state delineation manual to include information from the regional Supplements?

Yes, but not until the Corps releases the final versions of both Supplements. The Western Mountains, Valleys, and Coast regional supplement may change during the "interim" period, and Ecology does not want to adopt a rule that may have to be changed in year or two.

For a printer-friendly version of this information, see the related Focus Sheet: Focus On Wetland Delineation Forms.

If you have any questions on how to use the state delineation manual or about wetland delineation in general, email Tom Hruby at Ecology.