Avoidance and Minimization

Wetlands are protected by local, state, and federal laws. Applicants who propose to impact wetlands during development projects must apply mitigation sequencing before determining whether compensatory mitigation is appropriate. Mitigation sequencing 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 by preservation and maintenance operations during the life of the action;
  5. Compensating for the impact by replacing, enhancing, or providing substitute resources or environments; and/or
  6. Monitoring the impact and taking appropriate corrective measures.

Applicants are required by permitting agencies to show that they have followed the mitigation sequence and have first avoided and minimized impacts to wetlands wherever practicable. Use the information on this webpage as you design your project, to help you avoid and minimize wetland impacts as much as possible and to demonstrate to the permitting agencies that you have applied mitigation sequencing. Avoiding and minimizing wetlands may help save time and money on your project.

State and federal laws require avoidance and minimization of impacts whenever they can be reasonably accomplished through practicable alternatives. Practicable is defined in WAC 197-11-786 as an alternative that is available and capable of being done after taking into consideration cost, existing technology, and logistics in light of overall project purposes. The higher quality the resource and greater degree of difficulty in replacing the impacted habitat, the more important avoidance and minimization becomes.

Understanding the requirements for wetland impact avoidance and minimization

The information below is intended to assist development project applicants in understanding the requirements for wetland impact avoidance and minimization during development projects. The information will help applicants prepare more complete applications, which will facilitate faster review and decisions. 

The information is divided into three sections:

  1. Project Assessment: lists some potential ways to assess your site and project.
  2. Avoidance: lists potential ways to help you avoid wetland impacts where practicable.
  3. Minimization: lists potential ways to minimize impacts to wetlands where impacts cannot be avoided.

When submitting an application for review, the applicant must document how avoidance and minimization of wetland impacts were applied to the project design. A project description and site plans showing where avoidance and minimization design changes were made will inform the permit reviewer of the efforts taken.

Project Assessment

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 where potentially regulated resources are on your property 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.  

Following a complete examination of the various databases and mapping tools available, the applicant needs to have the site thoroughly assessed on the ground 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 are necessary to accurately characterize the resources on a site, such as wetland delineation and wetland rating.

> See a partial list of questions that should be answered in the project assessment process


Avoidance is the first step in the mitigation sequence. Avoidance means designing your project to avoid impacting wetlands during and after construction. For most types of impacts, wetland laws require applicants to demonstrate a need to impact a wetland, meaning there is no practicable alternative to reasonably accomplish the project 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 in the required mitigation sequence and begin to look for ways to mitigate for impacts that could be reasonably avoided through practicable alternatives. 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, starting with avoidance.

When a site has multiple wetlands, prioritize avoiding impacting the higher-quality wetlands. If fill is unavoidable, it is better to fill a Category III or IV wetland than a Category I or II wetland. This will also reduce mitigation requirements, which will save 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 practicable efforts have been made to avoid impacts to the resource. 

> See a partial list of examples of avoidance techniques


Minimization is the second step in the mitigation sequence. Minimization means reducing the amount of wetland impacts as much as is practicable when the impact is 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 that there is no reasonable, practicable alternative to accomplish the proposed action, applicants are still required to minimize the impacts. Minimization reduces the extent of wetland impacts, either in area or in function. There are many steps in the design process that can incorporate impact minimization. Most of the example techniques for avoidance can also be used to minimize impacts. Just as with avoidance, documenting the steps taken to minimize resource impacts is required.

Low Impact Development is a stormwater and land use strategy that tries to mimic the natural processes on pre-developed (typically forest) land that makes rainfall soak into the ground or get used by plants instead of becoming runoff. It emphasizes conservation, use of on-site landscape features, site planning, and distributed stormwater management practices that are integrated into project design. For example, reducing the amount of plants and soil disturbed during site development helps rainfall be caught by plants and soak into the ground instead of running directly into a gutter. Carefully applied low impact development techniques can help minimize impacts to wetlands.

> See a partial list of examples of minimization techniques

No hard line exists to determine when enough avoidance and minimization efforts have been applied to a particular project. Many factors must be considered together on a project-specific basis to decide when these requirements have been met. Careful consideration of these techniques and thorough documentation of your avoidance and minimization efforts will help speed your way through the permitting process.

If you have questions about the wetland permitting process, contact a wetland specialist that is listed for the county that your project is located.


Back to Top



Avoidance and minimization checklists