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Compensatory Mitigation Options

Options for providing compensatory mitigation for unavoidable wetland impacts vary depending on local circumstances and project requirements. Mitigation options may include using mitigation value from a WSDOT mitigation bank, advance mitigation, or unused credit from an existing mitigation site. Alternatively, mitigation credit may be purchased from a certified third-party mitigation bank or In-Lieu Fee Program. If these options are unavailable at your location, the project team may elect to develop new permittee-responsible mitigation designed and constructed to meet the specific needs of the project.

Understanding Mitigation Needs

Considering mitigation options at any stage of a project requires an estimate of impacts to wetlands and the amount of mitigation that is needed to compensate for project impacts. WSDOT has developed Wetland and Buffer Impact Assessment Guidance (pdf 465 kb) that describes the process used to determine wetland and buffer impacts after the NEPA process is complete.  This guidance provides a process and checklist for assessing impacts.  The amount of mitigation needed can be obtained with the WSDOT Mitigation Area Calculation Guidance (pdf 70 kb). This guidance details how to estimate the acreage of mitigation required for a project during the Permitting phase. Additional resources related to regulatory requirements for mitigation are included in the Mitigation Toolbox.

Evaluating Mitigation Options

The following mitigation options (pdf 25 kb) are discussed in the latest Federal regulations governing compensatory mitigation. The list below is in the generally preferred order of consideration. Early coordination with regulatory agencies to ensure that the types of mitigation available will be suitable for mitigating project impacts is prudent. When making decisions about compensatory mitigation options, the project team selects the most cost-effective option that yields the greatest environmental benefit.

Using Existing WSDOT Mitigation Value

Determine if existing WSDOT investments have available and appropriate mitigation value.

Purchasing Existing Third-Party Credit

Purchasing mitigation credit from a certified third-party mitigation bank or In-Lieu Fee program may be a cost-effective option available if your project occurs in a sponsors service area. The actual cost of mitigation credits will vary and are negotiated with the source sponsor. It is important to contact sponsors directly to ensure the availability of appropriate credit.

  • Third-Party Mitigation Bank Credit - Using mitigation credit from a certified wetland mitigation bank with credits available to purchase is preferred because the mitigation is developed in advance of project impacts.
  • In-Lieu Fee Credit. Purchase of mitigation credit from an in-lieu fee program that has been constructed includes a component of advance compensation. If the program has been approved, but the mitigation has not been constructed, this option may or may not be advantageous to both WSDOT and the resource.

Developing New Mitigation

If existing credit from constructed sites is unavailable it may be necessary to develop new compensatory mitigation. Permittee-Responsible Mitigation involves WSDOT developing mitigation and includes design, permitting, construction, monitoring and long-term management.

  • Advance mitigation is a form of permittee responsible mitigation that is constructed and developed during the scoping phase.  Because the mitigation is in advance of project impacts, mitigation ratios may be more favorable.
  • Concurrent Mitigation is permitted constructed and funded as part of a transportation project. Typically higher ratios are required to address reduced certainty of mitigation site success and temporal losses in wetland function between the time of the impact and when the mitigation site is fully functional.

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