Mitigation

• Author: Stephen M. Johnson
• Pages: 266-290

266

Chapter 7

Mitigation

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

 Restoration

 Enhancement

 Creation

 Preservation

Photo 34 Wetlands Restoration - USDA

Photo on

http://commons.wikimedia.org/wiki/File:

Wetlands_restoration_hughes_co_south_

dakota.jpg

267

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