The provisions of Section 408 apply to works that were built by the Corps and are locally maintained (such as local flood control projects) or operated and maintained by the Corps (such as locks and dams). Proposals submitted for Section 408 review and approval undergo a rigorous engineering, policy and environmental review by the Corps and, if required, independent external peer review. As a Federal action, the environmental review must meet the requirements of the National Environmental Policy Act (NEPA).
Examples of modifications that might be proposed at a Corps lock or dam are hydropower generating facilities and fish passage channels and structures. Examples of modifications proposed at local flood control projects are major levee or wall modifications to address levee accreditation by the Federal Emergency Management Agency (FEMA). Nation-wide efforts by FEMA directed at map modernization of its floodplain designations have resulted in an increase in the number of requests for Section 408 review by non-Federal sponsors for many older flood control projects. The sponsor requests may include measures directed to repair or rehabilitate older flood control structures. Additionally, highway department road and bridge projects may require alterations to Corps projects and need review and approval under Section 408.