Author:Stephen M. Johnson
Chapter 7
When the Corps issues a Section 404 permit that authorizes the discharge of dredged or fill
material into wetlands, at least some wetlands are likely to be destroyed or degraded, even
though the permit applicant has taken measures to avoid and minimize the impacts. For
that reason, the Corps has, from the early days of the Section 404 permit program,
included conditions in permits that require the permittee to offset those environmental
harms by providing compensatory mitigation.
I. Types of Mitigation
There are basically four types of compensatory mitigation:
Restoration of wetlands involves re-establishing or
rehabilitating wetlands with the goal of returning
natural or historic functions to a former wetland or a
degraded wetland. See 33 C.F.R. § 332.2. Wetlands
are re-established or rehabilitated by manipulating the
physical, chemical or biological characteristics of a
site. Id. For instance, a wetland that has been drained
may be restored by removing underground drain tiles,
plugging open ditches, or building small dikes. See
Michigan Department of Natural Resources, Wetland
Restoration Techniques. Restoration often provides
the most cost-effective improvement in wetland
function. See U.S. Department of Agriculture,
Engineering Field Handbook, Part 650, Chapter 13,
Wetland Restoration, Enhancement or Creation 13-2
(Apr. 2008) [hereinafter “USDA Engineering Field
Photo 34 Wetlands Restoration - USDA
Photo on
Handbook”]. Sites that will be restored often have wetlands soils and some wetland plants
and mainly require re-establishment of the former hydrology and topography.
Enhancement of wetlands involves manipulating the physical, chemical or biological
characteristics of an existing wetland to improve a particular function or functions. See 33
C.F.R. § 332.2. For instance, enhancement projects might involve diverting a small stream
into a wetland to change the water depth or planting different vegetation in the wetland in
order to provide habitat for different varieties of fish, birds, or other wildlife. See USDA
Engineering Field Handbook 13-2. By improving some functions of wetlands, though,
enhancement projects might impair other functions. See 33 C.F.R. § 332.2. For example,
by improving the habitat for some varieties of fish and wildlife, a project may degrade the
habitat for others. Enhancement projects do not generally increase the acreage of existing
wetlands. Id. While restoration and enhancement projects can both take place in degraded
wetlands, restoration projects focus on returning the site to a prior condition, while
enhancement focuses on changing the functions of the site, without regard to the prior
condition of the site. Wetlands enhancement projects generally require more management
and are more expensive than wetlands restoration projects. See USDA Engineering Field
Handbook 13-2.
Creation (or establishment) of wetlands involves manipulating the physical, chemical or
biological characteristics of land to establish wetlands in uplands or on lands where
wetlands did not previously exist. See 33 C.F.R. § 332.2. Wetland creation is the most
difficult type of compensatory mitigation because it requires bringing water to a site where it
does not naturally occur and establishing vegetation on soils that are not hydric soils. See
National Oceanographic and Atmospheric Administration, An Introduction and User’s Guide
to Wetland Restoration, Creation and Enhancement 11. Consequently, wetland creation is
more expensive and requires more management than other mitigation options. See USDA
Engineering Field Handbook 13-2. Wetlands are often created for only one function, such
as providing wildlife habitat, educational opportunities, or improving water quality of non-
point source runoff. Id. If successful, though, wetland creation provides an increase in the
functions and acreage of wetlands. See 33 C.F.R. § 332.2
Preservation of wetlands involves the permanent protection of ecologically important
wetlands through the implementation of appropriate legal and physical mechanisms, such
as conservation easements or transfer of title. See 40 C.F.R. § 230.93(h). It does not
provide an increase in wetland functions or acreage. See 33 C.F.R. § 332.2
The purpose of compensatory mitigation is to develop long term self-sustaining aquatic
resources that offset adverse effects and are not dependent on human intervention after
the mitigation has been established. See U.S. Army Corps of Engineers, Sacramento
District, Mitigation.
Of the four types of compensatory mitigation, restoration is generally the preferred option

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