Environmental Mitigation Office
James K. Polk Building, Suite 900
505 Deaderick Street
Nashville, Tennessee 37243
The Tennessee Department of Transportation (TDOT) Environmental Mitigation Office is responsible for providing compensatory mitigation to offset unavoidable stream and wetland impacts from transportation projects through a process referred to as compensatory mitigation. According to the U.S. Environmental Protection Agency (EPA) Section 404 of the Clean Water Act, compensatory mitigation methods include restoration (re-establishment or rehabilitation), establishment (creation), enhancement, and/or preservation of wetlands, streams and other aquatic resources for the purposes of offsetting unavoidable adverse impacts. Compensatory mitigation is required for certain TDOT transportation projects, as part of the permitting process through the Tennessee Department of Environment and Conservation (TDEC) and the U.S. Army Corps of Engineers (USACE).
The Mitigation Sequence
The 1990 Memorandum of Agreement (MOA) between the EPA and the Department of the Army established a three-step process to help guide decisions and determinations regarding the type and level of mitigation required. The 2008 FINAL Mitigation Rule superseded much of th e1990 MOA; however, the three-step process still remains a valid tool for the Environmental Mitigation Office. The TDOT Environmental Mitigation Office utilizes the following mitigation sequence to ensure that compensatory mitigation is being provided according to Section 404 Clean Water Act regulations:
- Step 1: Avoid – Adverse impacts to streams, wetlands, and other aquatic resources are to be avoided and no discharge shall be permitted if there is a practicable alternative with less adverse impact.
- Step 2: Minimize – If impacts to streams, wetlands, and other aquatic resources cannot be avoided, appropriate and practicable steps to minimize impacts must be taken.
- Step 3: Compensate – Appropriate and practicable compensatory mitigation is required for unavoidable adverse impacts which remain.
Compensatory Mitigation Methods
In those cases where compensatory mitigation is required in order to offset unavoidable adverse impacts to streams, wetlands, or other aquatic resources, the TDOT Environmental Mitigation Office provides the required mitigation through the use of restoration, establishment, enhancement, and/or preservation. A description of each of these compensatory mitigation methods is shown below.
- Restoration – re-establishment or rehabilitation of a stream, wetland, or other aquatic resource with the goal of returning natural or historic functions and characteristics to a former or degraded resource
- Establishment – development or creation of a stream, wetland, or other aquatic resource where a resource did not previously exist through manipulation of the physical, chemical, and/or biological characteristics of the site
- Enhancement – activities conducted within streams, wetlands, or other aquatic resources which heighten, intensify, or improve one or more resource functions. Enhancement is typically undertaken for a specific purpose, such as to improve water quality, flood control, or wildlife habitat
- Preservation – permanent protection of ecologically important streams, wetlands, or other aquatic resources through the implementation of appropriate legal and physical means (conservation easements, title transfers, etc.)
Compensatory Mitigation Mechanisms
The TDOT Environmental Mitigation Office utilizes various mechanisms for providing compensatory mitigation to offset unavoidable impacts from transportation projects. By using the mechanisms shown below and working with the TDOT Ecology and Permits Office staff, the required compensatory mitigation is obtained, and the environmental permits necessary for construction of the transportation project are acquired.
- Mitigation Banks - A mitigation bank is a wetland, stream or other aquatic resource area that has been restored, established, enhanced, or preserved. This resource area is then set aside to compensate for future impacts to aquatic resources resulting from permitted activities.
- In-Lieu Fee Programs - A permit applicant may make a payment to an in-lieu fee program that will conduct wetland, stream or other aquatic resource restoration, creation, enhancement, or preservation activities. In-lieu fee programs are generally administered by government agencies or non-profit organizations that have established an agreement with the regulatory agencies to use in-lieu fee payments collected from permit applicants.
- Permittee-Responsible Mitigation - A permittee may be required to provide compensatory mitigation through an aquatic resource restoration, establishment, enhancement and/or preservation activity. This compensatory mitigation may be provided at or adjacent to the impact site (i.e., on-site mitigation) or at another location, usually within the same watershed as the permitted impact (i.e., off-site mitigation).
*The TDOT Environmental Mitigation Office is responsible for the design and implementation of compensatory mitigation plans, as well as ensuring that all mitigation projects are developed and documented in accordance with applicable state and federal regulations and guidance.
Currently, TDOT has stream mitigation needs across the state and wetland mitigation needs in portions of the Upper Cumberland River Service Area, as well as in East Tennessee. If you are a mitigation banker, landowner, or are interested in partnering with TDOT to provide compensatory mitigation, please contact our office.
Landowners Interested in Partnering with TDOT
If you are a landowner that is interested in partnering with TDOT in order to provide compensatory mitigation for unavoidable stream and/or wetland impacts, please review the Helpful Links section below, and contact our office with any questions. General characteristics of ideal stream and wetland mitigation sites are as follows.
|Ideal Stream Mitigation Sites||Ideal Wetland Mitigation Sites|
|Have unstable or eroding stream banks||Are wet areas located in agricultural land|
|Have stream lengths of at least 1,000 feet (longer stream length is better)||Are wet fields which have previously been ditched or drained|
|Have channels whose width (from top of bank to opposite top of bank) is relatively small||Are areas with stressed crops due to prolonged water|
|May go dry in the summer or flow year round||Are sites that are large in area (20 acres or larger is better)|
|Contain accessible and obtainable property on both sides of the stream channel
|The landowner controls mineral rights
|Are either public or private property
Mitigation Site Protection
Both stream and wetland mitigation sites must be permanently protected. Protection can be accomplished either through an easement or sale of the property to the State of Tennessee. Landowners can be compensated for property easement or ownership, but only if they are willing sellers and the streams or wetlands within their property meet program criteria.
EPA: Section 404 of the Clean Water Act - 1990 Memorandum of Agreement (MOA) between the EPA and Department of Army
Current Stream Mitigation Estimates