Wetland mitigation is how a project makes up for wetland impacts it can’t avoid. Under Section 404 of the Clean Water Act, a project that fills or alters regulated wetlands or streams must first avoid and minimize those impacts. If unavoidable impacts remain, the permit usually requires compensatory mitigation: restoring, creating, enhancing or, in some cases, preserving wetlands or streams elsewhere to replace the lost functions.
The mitigation sequence
Mitigation in the federal sense is a sequence, not a purchase:
- Avoid. Design the project to stay out of wetlands and streams where practicable.
- Minimize. Reduce the footprint, the duration or the severity of impacts that can’t be avoided.
- Compensate. Offset what’s left with compensatory mitigation.
The Corps reviews the avoid and minimize steps closely on individual permits. Showing that you redesigned around wetlands is often what makes the permit approvable and the mitigation smaller.
Three ways to provide compensatory mitigation
The 2008 federal Mitigation Rule (33 CFR Part 332), issued jointly by the Corps and EPA, sets the framework and generally prefers these options in this order:
- Mitigation bank credits. A mitigation bank is a site where wetlands or streams have already been restored, created, enhanced or preserved under an approved mitigation banking instrument. Banks sell credits, units representing functions gained at the bank. When you buy credits, the legal responsibility for the mitigation transfers to the bank sponsor. Banks are preferred because the work is usually done, or under way and monitored, before the impact happens.
- In-lieu fee programs. A permittee pays a government or nonprofit sponsor, which uses the fees to carry out mitigation projects. Responsibility also transfers to the sponsor.
- Permittee-responsible mitigation. The permittee restores or creates wetlands, on site or off site, and keeps full responsibility for success, including monitoring and long-term protection.
Two terms come up in every mitigation discussion: – Service area: the area a bank’s instrument allows it to serve. Your project generally must fall within the bank’s service area. – Credit type: for example bottomland hardwood, pine savanna or stream credits. It should match the type of resource impacted.
See buying credits vs. establishing your own and stream mitigation.
What goes into a wetland mitigation plan
Whether it’s for a bank or a permittee-responsible site, a mitigation plan covers:
- Objectives and the functions being replaced
- Site selection, with a watershed rationale
- A baseline assessment of current conditions
- How credits are calculated
- The work plan: hydrology, grading, planting and invasive control
- Measurable performance standards
- A monitoring schedule
- A long-term management plan
- An adaptive management plan
- Financial assurances
For banks, the Interagency Review Team (IRT) of federal and state agencies reviews the instrument. Credits are released in stages as the bank meets its milestones. See what an IRT is.
Mitigation banks in practice: two Gulf Coast examples
Texas Flat Mitigation Bank (USACE Mobile District). Texas Flat is a 1,985-acre bank on a former pine plantation that had been under active timber management since the 1930s. Silviculture, including bedding that changed surface hydrology and soils, had damaged its wetlands and streams. The bank now includes more than 6 miles of streams and more than 1,700 acres of wet pine flats and bottomland hardwood forest, with both stream and wetland credits. It was approved by the USACE Mobile District in 2013. Working for the owner, Soterra LLC, Cypress developed the prospectus and mitigation banking instrument and the studies behind them: wetland delineation of all 1,985 acres, a threatened and endangered species study, habitat and stream mapping, wetland function and stream assessments, restoration success criteria and a baseline ecological site profile. Cypress also handled design, permitting, monitoring and construction engineering and inspection.
Little Biloxi River Mitigation Bank (coastal Mississippi). This 166-acre bank in the USACE Mobile District, owned by The Conservation Fund, was the second coastal Mississippi bank with stream credits. Its credit types are pine savanna, stream and bottomland hardwood forest. Cypress did the wetland delineation, threatened and endangered species study, habitat and stream mapping, ecological function and stream assessments, restoration success criteria and the baseline ecological site profile, along with design, permitting, monitoring and construction. Cypress carried the bank through to completion, with 100% of its credits released.
Both banks show the same thing: mitigation that works starts with good baseline science and a realistic plan for hydrology.
Common mistakes
- Buying the wrong credit type, or credits from a bank whose service area doesn’t cover the project
- Proposing a permittee-responsible site that won’t hold water
- Underestimating monitoring and long-term management costs and time
- Skipping avoidance and minimization, which can make mitigation larger than it needs to be
- Ignoring Gulf Coast factors such as salinity, subsidence and invasive species
How Cypress helps
Cypress Environment & Infrastructure works on both sides of wetland mitigation. We help permit applicants find the right credits or design a permittee-responsible site, and we help landowners establish mitigation banks from prospectus through credit release, across Mississippi, Alabama, Florida and Louisiana. Learn more about our mitigation banking services, or contact Cypress to talk through your project.
Frequently asked questions
What is wetland mitigation?
Compensating for unavoidable impacts to regulated wetlands or streams by restoring, creating, enhancing or preserving similar resources elsewhere, usually as a condition of a Section 404 permit.
What is a wetland mitigation bank?
A site where wetlands or streams have been restored, created, enhanced or preserved under an approved banking instrument. The bank sells credits to permittees, and responsibility for the mitigation transfers to the bank sponsor.
What are wetland mitigation credits?
Units representing the aquatic functions gained at a mitigation site. Permittees buy credits of the right type from a bank whose service area covers their project.
What is included in a wetland mitigation plan?
Objectives, site selection, baseline conditions, credit calculations, a work plan, performance standards, monitoring, long-term and adaptive management, and financial assurances.
Which type of mitigation does the Corps prefer?
Under the 2008 Mitigation Rule, the Corps generally prefers mitigation bank credits, then in-lieu fee programs, then permittee-responsible mitigation, subject to what best replaces the lost functions.