Wetland and stream reconnaissance and assessment

This page contains technical information used by qualified wetland biologists (pdf 566 kb) for completing wetland and stream reconnaissance and assessment on Washington State Department of Transportation (WSDOT) projects. Wetland and stream reconnaissance and assessment document existing conditions and allow project engineers and designers to avoid and minimize impacts to wetlands and other waters. Staff use assessments of impacted wetlands and streams to design compensatory mitigation. Wetland and stream reconnaissance and assessment provide information for National Environmental Policy Act (NEPA) documentation and permit applications, including the joint aquatic resource permit application (JARPA)

  • Wetland and stream reconnaissance identifies potential wetlands and other waters and approximates their locations during early planning and scoping stages of projects.
  • Wetland and stream assessments determine the location, boundary, and area of wetlands and their rating, classification, and functions. It also includes other waters such as lakes, streams, and ditches and determines their location, boundary, and classifications.

Read Chapter 431: Wetlands in the WSDOT Environmental Manual (EM) for policies regarding wetlands. Go to the EM to find the laws and policies that drive the work we do. Come here to our webpages to learn how to do the work for WSDOT projects.  See the Determining jurisdiction of wetlands and other waters page for more on law and policy regulating waters of the US and waters of the state.

If archeological materials or human remains are discovered during fieldwork, use the Cultural resources and wetlands (pdf 2,242 kb) document to comply with federal and state cultural resource laws and regulations.

Information on this page:

Wetland and stream reconnaissance

During the planning and scoping phase of a project document reconnaissance, also referred to as wetland and stream inventory, in a Wetland and Stream Inventory memo.

To determine presence of wetlands or other waters in the project vicinity, follow Procedure and Task 300-a: Determining presence or absence of wetlands, streams, and other waters for planning and scoping (pdf 254 kb). Follow our Sensitive areas naming conventions (pdf 562 kb) to ensure wetlands and other waters are clearly and consistently identified in the field and on plans and figures.

Use the WSDOT GIS Workbench to estimate presence of sensitive resources in the project vicinity and aid in background research. External partners may access this information from other data sources. Review the following information in preparation for wetland field work:

  • National Wetland Inventory.
  • Local wetland inventories.
  • Hydric soils.
  • Topographic maps.
  • Satellite imagery and infrared and true-color aerial photographs.
  • WSDOT mitigation site locations.

Make a field visit(s) to identify potential wetlands and other waters and approximate their locations.

Prepare a Wetland and Stream Inventory memo including:

  • Description and map of the study area.
  • Approximated wetland boundary, area, and category.
  • Estimated locations of other waters.

Wetland and stream assessment

During the environmental review and permitting phase of a project, coordinate with the project team to determine the necessary documentation for a given project. A qualified biologist does a wetland and stream assessment resulting in a Wetland and Stream Assessment Report (WSAR). A WSAR supports NEPA documentation, permit applications, and potential mitigation.

Review Procedure and Task 431-a: Assessing Waters and Wetlands (NEPA) (pdf 271 kb) to learn how to coordinate a wetland and stream assessment and obtain a WSAR. Wetland and stream assessment includes the same office tasks prior to field work as described above in the wetland and stream reconnaissance section, Follow our Sensitive areas naming conventions (pdf 562 kb) to ensure wetlands and other waters are clearly and consistently identified in the field and on plans and figures.

If a Wetland Discipline Report is deemed appropriate, use the Wetland Discipline Report Checklist (pdf 49 kb) to satisfy NEPA. Wetland Discipline Reports generally include documentation of existing conditions, impact analysis, and conceptual mitigation. Avoid duplicating information. Coordinate with your project team to “right size” your documentation. For example, a Discipline Report may end up as a short document, covering project description, summarizing existing conditions and impact analysis, and including the WSAR and conceptual mitigation memo as attachments.  See our webpages on the EA/EIS process and Prepare quality environmental documents for more information on NEPA documentation.

If a Vegetation Discipline Report is deemed appropriate, use the Vegetation Discipline Report Checklist (pdf 54kb), and the Vegetation Discipline Report Template (pdf 73 kb) to aid document development and review.   

Use the Generic Scope of Work for Delineation (docx 54 kb) to help build the wetland and stream delineation and assessment section in your consultant contracts.

Wetland and stream assessment report

Follow Procedure and Task 431-a: Assessing Wetlands Waters and Wetlands (NEPA) (pdf 271 kb) and use the Wetland and Stream Assessment Report (doc 354 kb) template.

The WASR documents the wetland and stream assessment and includes:

Future mitigation sites also require an assessment to determine the boundary between existing wetland areas, such as preservation or enhancement, and new wetland establishment areas.

Reports are valid for five years from the date of the field work. If the project is delayed, review field work and update the report before JARPA submittal.

Wetland assessment

Delineation Methods

Use the Corps of Engineers Wetlands Delineation Manual for delineation methods outlined by the US Army Corps of Engineers (the Corps). The Corps considers wetland delineations valid for five years from the date of field work.

Determine which Land Resource Region (LRR) your project is located in using the Major Land Use Resource Areas map (Natural Resources Conservation Service (NRCS) Agriculture Handbook 296) (pdf 626 kb).

Follow our Sensitive areas naming conventions (pdf 562 kb) to ensure wetlands and other waters are clearly and consistently identified in the field and on plans and figures.

Delineation Tools

Use these tools, forms, guidance, and links for collecting vegetation, soil, and hydrology data for wetland delineation.

Wetland determination data forms

Find the WSDOT-created electronic version of the Corps Wetland Determination Data Forms (ftp server) for both Arid West (AW) and Western Mountains, Valleys, and Coast (WMVC) Regions. The forms require a full Windows operating system and Excel. Mobile versions do not support the macros used in the forms.

Built-in features of the WSDOT forms include tools for inserting scientific plant names with their associated wetland indicator status (WIS), also referred to as “FAC status”, automated calculations, and dropdown menus for common responses.


Use the Plant Code List (pdf 271 kb) to record field data for plants commonly found in Washington. This list provides scientific and common names, native vs. introduced, and WIS of a subset of commonly encountered plants based on the 2016 National Wetland Plant List (NWPL).

A corresponding WSDOT auto-text macro for Microsoft Word inserts information when you enter plant codes, including scientific name, common name, and WIS. Find installation instructions, plant codes, and the macro file “Autotext_Plants.dotm” on the WSDOT public FTP server.

Poisonous and harmful plants to avoid

People working in the field should be aware of poisonous and harmful plants to avoid. Our online (pdf 7.7 mb) and print-friendly (pdf 7.8 mb) booklet provides information on common plants to avoid. If printing, from print settings select “print on both sides of paper” AND “flip on short edge”.


Reference the most recent versions of the U.S. Department of Agriculture (USDA) National Resource Conservation Service (NRCS) publications to describe soils on your project site:


The following tools support the collection and analysis of hydrologic characteristics of your site:

We may install shallow groundwater monitoring wells or piezometers during mitigation site selection, site design, or on mitigation sites during monitoring to gather groundwater information. These tools are less commonly used for wetland assessment, but may be used to gather additional hydrology information or in problematic situations. See our mitigation page for more information.

Rating forms

Before rating your wetland, use the boundary between Eastern and Western Washington (pdf 59 kb) map to determine what geographic area your project is located in. Refer to Washington State Department of Ecology’s (Ecology) most recent version of the Washington State Wetland Rating System appropriate for your region.

Use the following WSDOT adapted data forms to rate wetlands in your study area.

Western Washington forms:

Eastern Washington forms:

Classification methods

We use two different classification methods for wetland assessment.

Functions assessment

Potentially impacted wetlands require functions assessment.

Use the Wetland Functions Characterization Tool for Linear Projects (pdf 96 kb) referred to as the Best Professional Judgement (BPJ) tool. A nationally or state recognized rapid functional assessment method isn’t available. BPJ was developed by WSDOT, along with regulatory and resource agencies and one tribe, to characterize wetland functions for WSDOT projects. This tool evaluates and documents functions of potentially impacted wetlands on your project, including water quality, hydrologic, biological, and social functions.

Washington State Department of Ecology’s Credit/Debit method is also an acceptable functional assessment method. It calculates if a proposed wetland mitigation project adequately replaces lost functions and values of impacted wetlands. Use this method primarily for in-lieu fee mitigation proposals. The BPJ tool is preferable for most WSDOT projects as applying the Credit/Debit method to projects with more than a few wetlands is challenging.

Wetland and stream buffers

Local agencies require regulatory wetland and stream buffers. Review wetland and stream regulations in local city or county municipal codes or critical areas ordinances to determine regulatory buffer requirements for your project.

Some projects may span several jurisdictions including cities, counties, and tribal lands. For example, you may have a project where some wetlands fall:

  • Within the city limits - apply the city’s buffer widths.
  • Within the unincorporated county - apply the county’s buffers.

On the boundary between jurisdictions - apply the wider buffer to the feature unless a project specific variance is warranted.

Stream assessment

During the environmental review and permitting phase of a project, identify streams within a project’s area of potential effect (APE). Gather the following stream information and document in the WSAR:

Stream delineation methods

Follow the Corp’s methodology for OHWM identification in non-tidal areas established in the Corps regulatory guidance letter 05-05 .

Use MHHW to delineate tidally influenced waters. MHHW is the average of the higher high water height of each tidal day observed over the National Tidal Datum Epoch, a 19-year period of data collection that informs mean values of tidal datums. Find MHHW datums from specific monitoring stations on the NOAA Tides and Currents website and help interpreting the data on their Tidal Datums page.

Follow our Sensitive areas naming conventions (pdf 562 kb) to ensure wetlands and other waters are clearly and consistently identified in the field and on plans and figures.

Ditch assessments

If a project proposes potential impacts to ditches, the project engineer’s office (PEO) requests that a qualified wetland biologist (pdf 566 kb) identify potentially impacted ditch sections during the wetland assessment field work. The PEO provides the biologist with plan sheets identifying potentially impacted ditch sections, known flow directions, and relevant infrastructure such as culverts and stormwater features. Review Procedure and Task 431-a: Assessing Waters and Wetlands (NEPA) (pdf 271 kb) for more details. We don’t make jurisdictional calls, but can recommend a jurisdictional determination. The Corps is responsible for the final decision. See our US Army Corps of Engineers jurisdiction over wetlands and other waters page for more information.

Identifying jurisdictional ditches

Only assess ditch sections that will be potentially impacted to make a jurisdictional recommendation(s).

Assess ditches by walking ditch lines up gradient from the nearest downstream Water of the United States (WOTUS). When you cannot physically access the area, use background information, such as topographic maps, USGS StreamStats, and aerial photos to help identify where the ditch flows and if it drains to a WOTUS.

  • Use the WSDOT-created jurisdictional ditch recommendation field form (doc 18 kb) during field work to document ditch sections with proposed impacts. Surveyors survey jurisdictional ditch centerlines which are  included on plan sheets.  Biologists don’t need to flag jurisdictional ditch features unless they contain wetlands or streams. For more information on documenting ditches on plan sheets see the MicroStation application drawing patterns (pdf 1.65 mb).
  • Document ditches regulated as wetlands in the wetland section of the WSAR. Document ditches regulated as tributaries in the stream section of the WSAR.
  • Document ditches exempted form Corps jurisdiction on the field data form. Save it in the project file as internal documentation showing the ditch was evaluated and recommended as a ditch exempt from Corps jurisdiction.


Assessment guidance unique to WSDOT projects

Find information related to unique scenarios sometimes encountered on WSDOT projects below:

  • Road prisms (pdf 212 kb) – Use this document when projects include wetlands located adjacent to road prisms.
  • Cut slopes (pdf 229 kb) – Follow this guidance when projects involve wetlands on cut slopes.
  • Buffers across roadways (pdf 227 kb) – Refer to this information when wetland buffers are adjacent to or extend across roadways.
  • Isolated wetlands (pdf 41 kb) – Refer to these guidelines to determine if a wetland is isolated.