The National Academies

NCHRP 25-16 [Completed]

Guidance for Selecting Compensatory Wetland Mitigation Options

  Project Data
Funds: $224,784
Research Agency: A.D. Marble & Co., Inc.
Principal Investigator: Anne D. Marble
Effective Date: 3/1/1999
Completion Date: 7/1/2002

Background: Wetland banking is one of the alternatives for compensatory mitigation of unavoidable losses of wetlands as required by regulations established pursuant to Section 404 of the Clean Water Act. The Transportation Equity Act for the 21st Century (TEA-21) states that wetland banking will be given first consideration for mitigation of wetland losses caused by Federal-Aid Highway projects. Appropriate implementation of wetland banking can help agencies meet the national goal of "no overall net loss" of wetland functional capacity. Although federal agencies have published guidelines for the establishment, use, and operation of mitigation banks, issues need to be clarified and evaluated to ensure the selection of the most effective choice from among a wide range of mitigation approaches. For example, there is no agreed-upon basis for selecting between small-scale, dispersed mitigation versus consolidated mitigation approaches (of which wetland banking is one option).

Consolidated mitigation has the potential to improve the quality and effectiveness of wetland mitigation efforts; however, the degree to which these improvements can or have been attained is unknown, because there has not been adequate investigation into the use and results of mitigation banks and other consolidated applications. In addition, existing data on the results of compensatory mitigation for wetland impacts associated with highway projects have not been analyzed.

Some important potential benefits associated with consolidated mitigation (including wetland banks) are lower costs, higher wetland functional capacity per acre, improved sustainability, and easier management. Potential disbenefits associated with the use of consolidated mitigation include habitat alteration, landscape fragmentation, loss of functions, and watershed impacts. Transportation agencies need information about the relative benefits of consolidated mitigation versus small-scale, dispersed mitigation. Agencies also need to know when different alternatives will be more effective in meeting goals for wetland management and highway project development.

Objective: The objective of this research is to develop guidance for evaluating and selecting specific compensatory wetland mitigation options associated with development of transportation projects. The intent is (1) to evaluate and describe the relative effectiveness of small-scale, dispersed mitigation versus consolidated mitigation, including mitigation banks, and other compensatory mitigation options, and (2) to develop recommended criteria, performance expectations, and other guidance for their selection. The guidance should assist transportation- and resource-management agencies in evaluating the implications of specific mitigation options and should include criteria for considering an array of management issues (e.g., costs and wetland functions).

Tasks: This will be done through the following tasks.

Phase I. Project Design and Analysis: (1) Literature Search--Conduct a review of recent relevant literature and other documentation. The search should focus on small-scale, dispersed mitigation options as well as consolidated mitigation, including wetland banks. (2) Data Search--Identify, gather, and analyze available monitoring data, monitoring reports, and other information on wetland mitigation from state and federal agencies, resource management agencies, regulatory entities, local utilities, and other sources. (3) Agency Survey--Design, for panel approval, a national survey to obtain information on the performance and results of compensatory mitigation options. Include a broad distribution of wetland types and mitigation approaches. The survey results should refine and expand on the results of the data search (Task 2). Carry out the approved survey and analyze the results. (4) Interim Report and Panel Meeting--Submit an interim report summarizing the results of the analysis carried out in Phase I and a detailed outline of the decisionmaking process and guidance to be developed in Task 6. Provide more details on and recommend modifications to the Phase II work plan. Present the interim report findings at a meeting of the panel and obtain NCHRP approval to initiate Phase II.

Phase II. Process and Guidance Development: (5) Digest of Research in Progress--Under the direction of the NCHRP panel, prepare for publication a digest covering the results and findings of Phase I work. (6) Process Development--Using the data collected in Phase I, develop decisionmaking guidance, including criteria and procedures for selecting wetland mitigation options. (7) Final Report--Prepare a final report presenting the recommended decisionmaking guidance, criteria, and procedures. The report shall summarize the findings of Phase I and clearly document the basis for all conclusions and recommendations.

Status: The project is completed.

Product Availability: The interim results of the project were published as NCHRP Research Results Digest 251. The final report was published as NCHRP Report 482.

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