The objective of the Clean Water Act (CWA) is "to restore and maintain the chemical, physical, and biological integrity of the Nation's waters." Toward achievement of this goal, the CWA prohibits the discharge of dredged or fill material into wetlands, streams, and other waters of the United States unless a permit issued by the U.S. Army Corps of Engineers (Corps) .When there is a proposed discharge, all appropriate and practicable steps must first be taken to avoid and minimize impacts to aquatic resources. For unavoidable impacts, compensatory mitigation is required to replace the loss of wetland, stream, and/or other aquatic resource functions. The Corps is responsible for determining the appropriate form and amount of compensatory mitigation required. Methods of providing compensatory mitigation include aquatic resource restoration, establishment, enhancement, and in certain circumstances, preservation.
Mitigation is frequently required as a condition for issuing DA Permits and is intended to replace lost natural functions and values. When evaluating compensatory mitigation options, the Corps will consider what would be environmentally preferable. In making this determination, the Corps shall assess the likelihood for ecological success and sustainability, the location of the compensation site relative to the impact site and their significance within the watershed, and the costs of the compensatory mitigation project. Compensatory mitigation requirements shall be commensurate with the amount and type of impact that is associated with a particular DA Permit. Permit applicants are responsible for proposing an appropriate compensatory mitigation option to offset unavoidable impacts. Due to the difficulty of precisely quantifying the functional value of aquatic systems, including wetlands, the Chicago District currently accepts acreage replacement of the impacted system.
On April 10, 2008, the U.S. Army Corps of Engineers and U.S. Environmental Protection Agency issued the Final Compensatory Mitigation Rule to clarify how to provide compensatory mitigation for unavoidable impacts to the nation's wetlands and streams. The rule enables the agencies to promote greater consistency, predictability and ecological success of mitigation projects under the Clean Water Act. The new rule improves and consolidates existing regulations and guidance, to establish equivalent standards for all types of mitigation under the Clean Water Act Section 404 regulatory program. The rule does not change when compensatory mitigation is required, but it does change where and how it is required.
These equivalent standards take into account the inherent differences among mitigation banks, in-lieu fee programs, and permittee-responsible mitigation, in an effort to maximize the number of ecologically-successful compensatory mitigation projects that project proponents can use to offset their permitted losses of aquatic resources.
Compensatory mitigation is typically accomplished through either Mitigation Banks, In-Lieu Fee Mitigation, or Permittee Responsible Mitigation. Per the Final Compensatory Mitigation Rule there is a preference to the use of mitigation bank credits when available for the appropriate resource type and within the watershed. If permitted impacts are not located in the service area of an approved mitigation bank, or the approved mitigation bank does not have the appropriate number and resource type of credits available to offset those impacts, in-lieu fee mitigation, if available, is generally preferable to permittee-responsible mitigation.