Losses was established by the National Research Council to evaluate whether compensatory mitigation required of Section 404 permit recipients was contributing to achieving the CWA's overall objective of restoring and maintaining the quality of the nation's waters. In completing its work, the committee assumed that these steps were being followed and focused its efforts on the last step of reviewing compensatory mitigation for unavoidable permitted loss that could not be otherwise minimized.

First, the committee reviewed both the potential and the limits of scientific and technical abilities to replace the function of wetlands in watersheds. Second, the committee examined the likelihood that compensatory mitigation, as provided by the permittee or a third party (e.g., a mitigation bank or an in-lieu fee program), was being executed in a way to secure the goal of the CWA. The committee did not set up an experimental design for comparing in-lieu fee programs, permittee-sponsored and banking mechanisms for securing compensatory mitigation. Such an approach would have required the committee to identify a single mitigation target and then determine which mechanism would most likely meet it. There simply were no data that could be used for such an assessment. As a practical alternative, the committee chose to define the procedural requirements that were most likely to secure mitigation that would meet legal and ecological end points, and the committee compared mechanisms accordingly.

IMPORTANT TERMS

The scientific literature and wetland laws and regulations often attribute different meanings to the same term. Precise definitions are important because confusion about the exact meanings of terms can cloud the arguments being made. To avoid such confusion the committee adopted definitions for the following italicized words. A wetland is defined as “an ecosystem that depends on constant or recurrent, shallow inundation or saturation at or near the surface of the substrate” (NRC 1995). Wetland restoration refers to the return of a wetland from a disturbed or altered condition by human activity to a previously existing condition (NRC 1992). The wetland may have been degraded or hydrologically altered, and restoration then may involve reestablishing hydrological conditions to reestablish previous vegetation communities. Wetland creation refers to the conversion of a persistent upland or shallow water area into a wetland by human activity. Of these, constructed wetlands, also referred to as treatment wetlands, are created for the primary purpose of contaminant or pollution removal from wastewater or runoff (Hammer 1997). Wetland enhancement refers to a human activity that increases one or more functions of an existing wetland. Wetland preservation



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