Mitigation Plan Essentials

Header Image

Mitigation is a legal commitment to restore, create, and/or enhance a critical area to compensate for an unavoidable impact. Mitigation is required to replace the specific functions that would be lost as a result of impacts on critical areas. Submittal of a mitigation plan is required under Bellevue’s Critical Areas Ordinance for:

  • An “allowed use” project (LUC 20.25H.055) that involves unavoidable impacts on critical areas.
  • Any project that proposes impacts on critical areas as part of an overall improvement of critical area functions through the Critical Area Report process (LUC 20.25H.230).

Avoid, Minimize, Mitigate

You must design your project based on the existing conditions on and around your site.

You must demonstrate that you have designed your project according to the following sequence, referred to as mitigation sequencing. A narrative description and illustration are often necessary to demonstrate that mitigation sequencing was followed.

  1. Avoid impacts on critical areas, wherever feasible. Impacts are only allowed when no technically feasible alternative with less impact on critical areas exists.
  2. Minimize impacts that cannot be completely avoided.
  3. Mitigate for any remaining impacts that cannot be avoided or further minimized. Mitigation must be designed to replace the critical area functions that would be lost.

The city will determine if you have demonstrated that there is no technically feasible alternative with less impact on critical areas based on your permit application materials, so you should include:

  • A clear statement of your project’s goals
  • A clear, descriptive site plan showing the location of all existing infrastructure (e.g., power, gas, telephone, roads)
  • A discussion of all site planning alternatives you considered to meet your goals
  • A discussion of the degree to which alternatives that would have less impact on critical areas meet your project goals
  • A description of how your site planning has specifically minimized impacts on critical areas
  • An explanation of how your project costs would be affected by avoiding all impacts on critical areas

How much mitigation is enough?

Lost functions cannot be replaced instantaneously. It takes several years for wetland soils to develop, a stream buffer’s vegetation to grow dense, or an eroding slope to stabilize. Mitigation is determined based on a mitigation-to- impact ratio. The ratio is typically weighted to require a greater area of mitigation than the area of impact to make up for the loss of critical area function while a mitigation site is ”growing up.”

Each critical area type has specific mitigation and monitoring requirements that describe mitigation ratio, preferred location (onsite versus offsite), and type of mitigation (creation versus restoration or enhancement). For some critical areas, like wetlands, mitigation ratios are prescribed in the code; others require site-specific analysis to determine an appropriate ratio.

Plan Preparation

A mitigation plan can be prepared in phases (conceptual and final) to allow preliminary review by the city. Completing your mitigation plan in phases can speed up your permitting timeline and allow the city to provide input before you complete your design. Once the city has provided input on your conceptual mitigation plan and approved it, you can prepare your final plan. The city can then issue your Critical Areas Land Use permit, with the condition that your final mitigation plan be approved at the same time as your other development permits (e.g., clearing/grading or building permits).

The Critical Areas Handbook provides detailed information on conceptual mitigation planning, including site considerations and suggestions for appropriate native plants. Copies can be obtained at the City’s permit center for a nominal fee.

Plan Content Requirements (LUC 20.25H.210–225)

For your mitigation plan to be successfully processed, it must:

  • Clearly and accurately characterize and map existing conditions on the mitigation site
  • Evaluate the condition and function of each critical area based on scientifically valid methods
  • Demonstrate mitigation sequencing by explaining all measures taken to avoid, minimize, and mitigate unavoidable impacts
  • Clearly state goals and objectives of the mitigation plan, describing how equivalent or better critical area
  • functions will be achieved to compensate for the specific impacted functions
  • Contain detailed design drawings and specifications for the mitigation site, including: site drawings, scaled cross- sections, final grade elevations, an appropriately spaced planting plan, a plant species list showing the number of each plant species, and notes on proper site preparation (including temporary erosion and sediment control) and plant installation
  • Discuss ongoing maintenance practices to protect the mitigation site, including a minimum 5-year performance monitoring program with specific, measurable performance standards to evaluate mitigation site development
  • Include a contingency plan indicating actions and corrective measures to be taken if monitoring indicates performance standards are not being met
  • Include a statement of financial assurance that the mitigation will be constructed, maintained, monitored, and contingencies implemented, if necessary (often accomplished through posting a bond to the city)
  • Include a plan for restoring temporarily disturbed areas

Mitigation Takes Time and Money

  • Mitigation planning and permitting can add significant time and cost for additional design, permitting, and construction, plus five or more years of performance monitoring.
  • Mitigation construction is typically required in advance of or at the same time as project impacts, adding additional costs to project construction.

Additional Requirements for Wetland and Stream Impacts

  • Mitigation for impacts on wetlands or streams must meet the ratios and content standards of the U.S. Army Corps of Engineers (Corps) and Washington State Department of Ecology to receive federal and state permits required for construction.
  • Federal and state permits regularly require more than 5 years of performance monitoring.
  • Federal permits also require Endangered Species Act and National Historic Preservation Act documentation and interagency consultation lead by the Corps.