Calculating Credits and Debits for Compensatory Mitigation in Wetlands


Ecology has developed a tool for calculating when a proposed wetland mitigation project adequately replaces the functions and values lost when wetlands are impacted. It is called the Credit/Debit Method for short.  It was originally developed for use by King County in their in-lieu-fee program, but it has potential applications in other forms of compensatory mitigation.

The tool is designed to provide guidance for both regulators and applicants during two stages of the mitigation process:

  1. Estimating the functions and values lost when a wetland is altered, and
  2. Estimating the gain in functions and values that result from the mitigation.

The Department of Ecology, however, does not require the use of this method. This current guidance provides one method for determining the adequacy of compensatory wetland mitigation. It does not set any new regulatory requirements.

Download the Documents

Excel Files

Also available are two Microsoft Excel files that can be used to perform the calculations associated with Appendix E: Worksheets for Estimating the Adequacy of Wetland Mitigation. The first spreadsheet calculates the "debits" generated at the site where impacts are incurred. The second spreadsheet calculates the "credits" (increase in functions) at a mitigation site. The spreadsheets require the same information described in Appendix E and also contain the table of temporal loss factors and the risk factors.

More Information


Ecology highly recommends that users of this method take the training provided by the Department of Ecology. Scheduled classes can be found on the Coastal Training Program website.

Questions or Comments?


Back to Top