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Wetland Construction

Photo of a wetland delineation buffer


Wetland mitigation site construction
plans should include provisions for construction oversight and compliance monitoring by staff with the appropriate technical background and knowledge of permit requirements. Any deviations from mitigation plans and permits must be reported and approved by regional environmental staff and all permitting agencies prior to deviating from project plans and specifications.

Areas of compliance include:

  • Regulatory
  • Contract Provisions and Plan Sheets
  • Training

Regional Environmental Compliance Plans have been developed for each region to assure compliance with environmental requirements during construction. The basic elements include written procedures, training, tracking performance, conducting constructability reviews, and commitment tracking. 

Contract Provisions and Plan Sheets

WSDOT is also in the process of developing proven and acceptable methods for work in streams and wetlands. These methods would evaluate common permit conditions that would be linked to a standard library of specifications. This is intended to apply common permit conditions and integrate them into work procedures.


WSDOT provides environmental training for project inspectors tasked with overseeing compliance on project sites. Compliance training is available for all inspectors. Other current compliance-related training opportunities offered statewide include, but are not limited to:

  • Introduction to Wetlands
  • Environmental Permitting 101

Critical Areas Fencing

Wetland mitigation site construction plans include fencing of critical areas to prevent unintended and unpermitted impacts that could lead to violations of local, state, and/or federal environmental permits.

Critical areas may be wetlands, existing vegetation, or other aquatic resources such as streams and lakes that are shown in the plans. Existing critical areas must be identified and protected during construction. Wetland mitigation may include enhancing an existing wetland and/or creating a new one.

Project Delivery Memo #09-02 for High Visibility Construction Fencing (pdf 933 kb) revises the requirements for and use of high visibility fencing to define construction limits near wetlands and other sensitive areas.


Means and Methods

Compacted soils can decrease the success of wetland mitigation sites by changing surface hydrology and increasing competition pressure on native plants. Measures must be taken to minimize soil compaction.

These measures to minimize soil compaction include:

  • Using low ground pressure equipment.
  • Restricting ingress and egress points on the mitigation site.
  • Limiting paths or roadways within the site.
  • Ripping or tilling compacted soils.
  • Using mats such as steel or plastic plates or hog fuel to reduce compaction caused by equipment.

Roadside Work Plan

Special attention should be paid to the sequencing construction activity of wetland mitigation sites, and the timing shall not be compromised without prior permission from regulatory agencies. The following must be considered.

  1. Storage
  2. Staging
  3. Excavation
  4. Weed Control
  5. Planting
  6. Contingencies

Temporary Erosion and Sedimentation Control

Temporary Erosion and Sedimentation Control (TESC) plans will be physically present, easily accessible, and closely followed during construction. Training in TESC/Erosion Control is available at WSDOT. 


Planting and Irrigation Guidelines

Planting methods are included in the Standard Specifications, Division 8-02 Roadside Restoration. Special provisions will be included in the construction plans. Planting plans shall not be substantially compromised without prior permission from regulatory agencies.

When construction is complete, submit mitigation site as-built materials to comply with US Army Corps of Engineers 404 permits and Washington State Department of Ecology 401 Individual Water Quality Certifications.  WSDOT provides guidance on how to prepare as-built materials (pdf 133 kb) to satisfy these permits. 

As-built plans should also be sent to Doug Littauer (, the Wetland Monitoring Manager so the mitigation site may be accurately monitored and for record retention.