Avoiding & minimizing wetland impacts

As you design your project, the information we provide here is designed to help you avoid and minimize impacts to wetlands. This will help you demonstrate to the permitting agencies that you've applied mitigation sequencing. Avoiding and minimizing wetland impacts may help save time and money on your project.

Requirements to avoid and minimize development impacts

Wetlands are protected by local, state, and federal laws. Applicants with development proposals that may adversely affect wetlands must apply mitigation sequencing before permitting agencies consider compensatory mitigation options. In Washington, permitting agencies require applicants to show that they've followed the mitigation sequence and worked first to avoid and minimize impacts to wetlands whenever practicable before proposing compensation for the impacts. Practicable means "available and capable of being done after taking into consideration cost, existing technology, and logistics in the light of overall project purpose." 

Mitigation or mitigation sequencing, as defined in the State Environmental Policy Act (SEPA) rules, includes:

  1. Avoiding the impact altogether by not taking a certain action or parts of an action.
  2. Minimizing impacts by limiting the degree or magnitude of the action and its implementation by using appropriate technology, or by taking affirmative steps to avoid or reduce impacts.
  3. Rectifying the impact by repairing, rehabilitating, or restoring the affected environment.
  4. Reducing or eliminating the impact over time through preservation and maintenance operations during the life of the action.
  5. Compensating for the impact by replacing, enhancing, or providing substitute resources or environments.
  6. Monitoring the impact and taking appropriate corrective measures.

Avoiding and minimizing impacts are site-specific

Permitting agencies consider many factors to determine when applicants have met the requirements for avoiding and minimizing impacts. There are three phases to this process:

  1. Project assessment: Assess your site and project.
  2. Avoidance: Avoid wetland impacts where practicable.
  3. Minimization: Minimize impacts to wetlands where impacts cannot be avoided.

Avoiding and minimizing impacts becomes even more important when rare, high quality, or difficult to replace resources are involved.

Avoidance & minimization checklists

Use this avoidance & minimization checklist to show how your project has avoided and minimized wetland impacts. The checklist provides examples of how to accomplish avoidance and minimization during site analysis, project design, and construction.

Carefully considering the techniques and thoroughly documenting your efforts will help you prepare more complete applications, which facilitates faster review and decisions.

Project assessment is the process of investigating what natural resources, such as wetlands or streams, exist on your property and what kinds of protection are required by law. It’s important to understand what resources on your property might be subject to regulation so you can incorporate avoidance and minimization into your project design. It will also help you understand what must be compensated for if wetland impacts are unavoidable.

An individual project assessment begins by looking at the overall landscape setting, drainage basin, and existing natural and human-made features. Research should include databases for priority habitats (PHS maps), wetland inventory maps, fish use maps (Salmonscape), local critical areas maps, aerial maps, LIDAR, etc.

Have your site assessed for regulated resources

Following a complete examination of the available databases and mapping tools, the site must be thoroughly assessed for any and all regulated resources. Many sites contain unmapped streams or wetlands. Some may have threatened or endangered plants or animals that are not shown on any resource maps.

While mapping resources and previous studies provide important background information, they typically need to be supplemented with current site-specific information for permitting. Site-specific studies, such as wetland delineation and rating, are necessary to accurately characterize the resources on a site.

Avoidance is the first step in the mitigation sequence and means designing your project to avoid impacting wetlands during and after construction. For most types of impacts, wetland laws require applicants to demonstrate there is no practicable alternative to reasonably accomplish the project's purpose without the impact. Therefore, the impact is unavoidable.

Avoidance of impacts means that there is no direct loss of wetland area or function. It should be one of the first considerations in project design. Too often, project designers move quickly past the avoidance step and begin looking for ways to compensate for impacts that could be reasonably avoided.

At each level of review, local, state, and federal agencies have the authority to require feasibility studies, analysis of practicable alternatives, modifications to designs, and denial of a project if it is determined that a project does not demonstrate compliance with the mitigation sequence.

When a site has multiple wetlands, prioritize avoiding impacts to higher-quality wetlands. If fill is unavoidable, it may make more ecological sense to fill a lower-quality Category III or IV wetland than a higher-quality Category I or II wetland. This will also reduce mitigation requirements, saving time and money in project development. There are occasionally instances where wetland impacts are preferable, such as impacting a small Category IV wetland instead of a large, mature upland forest.

There are many steps in the design process that can incorporate wetland impact avoidance. Permit applicants are required to document that all efforts have been made to avoid impacts.

Minimization, the second step in the mitigation sequence, means reducing the amount of wetland impacts as much as possible when impacts are unavoidable. It might also mean impacting a wetland of lower quality instead of a higher-quality wetland.

After the project designer has completed the avoidance analysis and it is believed there is no reasonable, practicable alternative to accomplish the proposed action, applicants are still required to minimize wetland impacts.

Minimization reduces the degree to which wetland impacts affect an area, ecological functions, or both. You can incorporate actions to minimize impacts into many steps of the design process. Most avoidance techniques can also be used to minimize impacts. Just as with avoidance, you're required to document the steps taken to minimize impacts.

Using Low Impact Development (LID) also can lessen impacts to wetlands. This stormwater and land-use strategy tries to mimic the natural processes on pre-developed (typically forested) land that allows rainfall to soak into the ground or get used by plants instead of becoming runoff. LID emphasizes integrating conservation, use of on-site landscape features, site planning, and distributed stormwater management practices into a project design.

For example, reducing the amount of plants and soil disturbed during site development helps rainfall absorb into the ground instead of running directly into a gutter. Carefully applied LID techniques can help minimize impacts to wetlands.