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Advance Mitigation

What is Advance Mitigation?

Advance mitigation is a form of permittee-responsible mitigation constructed in advance of a permitted impact. An advance mitigation site needs to be planned, designed, permitted, and constructed before a transportation project can use any mitigation credit generated by the site. Advance mitigation can be done solely as an advance mitigation site or in conjunction with concurrent mitigation required by a federal, state, or local permit for a transportation project. Generally, a site must meet performance standards for two years following construction before it generates advance mitigation credit.

Advance Mitigation Benefits

Advance mitigation can be a cost effective and ecologically beneficial mitigation option.  The benefits of advance mitigation can include:

  • Permitting time may be reduced for future projects,
  • Mitigation ratios may be less than those required for concurrent mitigation, 
  • Sites can be larger and provide more ecological function, and 
  • Reduced monitoring and management costs because of efficiencies in size. 

Advance mitigation, along with mitigation banking is preferred by regulatory agencies because of the greater certainty of mitigation success and reduced temporal loss of wetland function. The US Army Corps of Engineers and the Washington State Departments of Ecology and Fish and Wildlife have developed guidance on advance mitigation.

How is Advance Mitigation different?

In contrast to mitigation banking, and In-Lieu Fee Programs, project proponents remain responsible for mitigation success, and advance mitigation value cannot be sold to a party that was not part of the mitigation site's development. 

Funding for advance mitigation can be a challenge because the mitigation site must be constructed several years before transportation project funding is available. Projects may obtain funding for early mitigation work from the WSDOT’s Advanced Environmental Mitigation Revolving Account (AEMRA). Contact Doug Swanson in the HQ Environmental Services Office for more information about AEMRA.

Early Planning and Design

Advance mitigation should be considered within the context of other feasible mitigation options during the project planning phase.  Planning for an advance mitigation site requires an early assessment of wetlands, and knowledge that future projects will have unavoidable wetland impacts

Design of an advance mitigation site should begin in the Scoping phase of the first project to use the mitigation credit.  Mitigation planning, coordination, design, construction, and the required 2-year establishment period may require a 3 to 4 year lead time before credit is available for construction impacts. Designing an advance mitigation site is similar to designing a concurrent mitigation site (pdf 98 kb).  The mitigation plan should identify how credit value will be created and how its use will be tracked.


Advance mitigation projects need to be permitted during the Scoping phase, before they are constructed. Separate permits are required for transportation project impacts during the Permitting phase. The ratio of mitigation to impact area depends on the condition and function of the advance mitigation site at the time credits are used. The process for using advance credits includes evaluating the suitability of mitigation value to compensate for project impacts and maintaining a ledger of available area.   


WSDOT’s Olympic Region currently has two advance mitigation sites; Spring Valley near Tacoma, and Jimmycomelately Creek near Sequim. The Southwest Region is currently developing a site at Tarlatt Slough at the south end of Willapa Bay.  Extra mitigation value may be available at these sites.  Contact the region wetland biologist for information.