Although the Coastal Act does not contain a specific definition for mitigation, CEQA and the associated CEQA guidelines do3. Under CEQA, mitigation includes all of the following:
1) Avoiding the impact altogether by not taking a certain action or parts of an action.
2) Minimizing impact by limiting the degree or magnitude of the action and its implementation.
3) Rectifying the impact by repairing, rehabilitating, or restoring the impacted 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 or providing substitute resources or environments.
This definition provides several alternative forms of mitigation, which are generally considered in sequence (i.e., avoidance first and compensation last).4 In mitigation by avoidance, adverse impacts are avoided altogether through alteration of project location, design, or other related aspects. Avoidance is a common form of mitigation used by the CCC. Staff should continue to emphasize mitigation by avoidance, since it is the best way to prevent direct adverse impacts to a wetland. Minimizing, rectifying, or reducing project impacts are forms of mitigation that diminish the severity of project related impacts. Although these forms of mitigation can result in alterations to the project design, the overall integrity of the project is usually preserved. Compensation includes mitigation undertaken to replace lost or adversely impacted habitat with habitat having similar functions of equal or greater ecological value. Typically, compensatory mitigation measures are included as an integral part of a project plan. This form of mitigation is often justified through arguments designed to show that the wetland acreage generated or enhanced through compensation is at least equal to the acreage lost through development. However, this concept of compensatory mitigation fails to recognize the ecological complexity of wetlands, their relationship to the landscape, and the fact that wetland functions may not be directly related to acreage. Compensating for the adverse impacts to wetland resources should only be considered as the last alternative, and only if there are no less environmentally damaging feasible alternatives.
Depending on the point of view, there are shortcomings to all forms of mitigation. Avoidance and minimization require project alterations that may be unacceptable to the project proponent, while compensation may lead to a net loss of wetland habitat and/or function. Thus, while there are several forms of mitigation, achieving adequate and successful mitigation is no simple matter.
The following sections of this document present information relating to compensatory mitigation involving wetlands. Throughout the remainder of this document the terms compensatory wetland mitigation, compensatory mitigation, wetland mitigation, and mitigation are considered synonymous.
3See, for example, CEQA Guidelines Section 15370.
4This sequencing approach to mitigation alternatives is clearly described in a Memorandum of Agreement between the Environmental Protection Agency and the Department of the Army (MOA, 1990).
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