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Mitigation Sequencing

The mitigation sequence spans the life of a project. Mitigation is a sequence of actions required by NEPA, SEPA, Governor's Executive Order 90-04, and WSDOT's Protection of Wetlands Policy. This involves understanding the affected environment and assessing transportation effects throughout project planning, development, and construction. This concept is not limited to wetlands, but the discussion below focuses on how the mitigation sequence applies to wetlands and WSDOT projects (pdf 71 kb).

Project staff are required to consider ways to make as little impact to wetlands as possible in all stages of the project. All unavoidable impacts to wetlands and other “waters” require compensatory mitigation. Any relevant and reasonable mitigation measures that could improve the project must be identified.

During every phase of project development through construction, each step in the mitigation sequence must be considered before proceeding to the next. This means that opportunities to avoid an impact must be evaluated before compensation for the impact is considered. Some of these sequencing activities may not be appropriate for some projects.  A short version of the mitigation sequence is:

Avoid > Minimize > Rectify > Reduce > Compensate > Monitor

Avoiding Impacts

  1. Mitigation sequencing may start in the Transportation Planning stage of the decision-making process with the development of alternatives. Otherwise reasonable options may be removed from further consideration at this stage because there are reasonable alternatives that avoid large wetland impacts. Advance mitigation options are considered if appropriate and available.  Additional information on WSDOT's policies during this stage is available in the Environmental Manual Chapter 200.
  2. Project Scoping involves identifying and evaluating alternative solutions to find the most cost effective and overall environmentally acceptable solution to a transportation need. An Environmental Review Summary is prepared, identifying potential environmental impacts, any proposed mitigation, environmental documentation requirements, and environmental permits. Early mitigation options should be considered and implemented if appropriate and feasible. Additional information on WSDOT's policies during this stage is available in the Environmental Manual Chapter 300.

Minimizing Impacts

  1. In implementing NEPA, Council on Environmental Quality (CEQ) regulations require that mitigation for impacts must be considered whether or not the impacts are significant. Mitigation measures are addressed in question 19a of the "Forty Most Asked Questions and Answers on the CEQ Regulations". Agencies are required to identify and include in the action all relevant and reasonable mitigation measures that could improve the action. In the Design and Environmental Review stage, the NEPA process develops and analyses alternative project footprints that avoid and minimize wetland impacts. As the design is advanced, any additional opportunities to avoid and minimize impacts must be considered. Compensation must be included as an integral part of the alternatives development and analysis process. In considering all disciplines, the least environmentally damaging practicable alternative is selected.  Additional information on WSDOT's policies during this stage is available in the Environmental Manual Chapter 400.
  2. A very similar mitigation sequence is required by the Corps of Engineers in Instruction Form B, Part 7 of the JARPA application during the Environmental Permitting stage. In the permitting phase, as the design is nearing 60%, affirmative steps to minimize impacts include design modifications such as steepening slopes, building retaining walls instead of using the default road prism slope, and asymmetrical widening on the non-wetland side. A compensatory mitigation plan for a specific site is submitted with the permit application for wetland impacts. Permit terms and conditions are included in contract documents.  Additional information on WSDOT's policies during this stage is available in the Environmental Manual Chapter 500.

Rectifying and Compensating for Impacts

  1. During project Construction, the contractor is responsible for implementing environmental commitments made during project development. Many of these commitments are to avoid unpermitted impacts. High visibility fencing (pdf 933 kb) protects wetlands that are adjacent to the work area, so unpermitted impacts are avoided. Best Management Practice techniques (BMPs) are implemented to minimize wetland impacts (see Stormwater BMPs). Permitted temporary impacts are rectified by re-planting when construction activities have ceased in that area. Additional information on WSDOT's policies during this stage is available in the Environmental Manual Chapter 600.

    During this phase, compensatory mitigation sites are constructed and monitored to insure they provide substitute resources for those lost. The mitigation sequence ends when the Corps provides written agreement that the compensatory wetland mitigation site has met its goals, objectives and performance standards.

Reducing The Impact Over Time

Usually, this does not apply to wetlands and WSDOT projects.

Monitoring The Impact

  1. Under SEPA and Executive Order 90-04 (pdf 27 kb), compliance assurance monitoring is conducted to insure that unpermitted impacts are avoided. Appropriate corrective measures are implemented when needed.

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