This chapter defines rehabilitated structures as existing structures that are not to be replaced, but may be substantially repaired, modified, or extended as part of the project. Common examples of rehabilitated structures include, but are not limited to:

If a structure is to be rehabilitated, the standards and criteria presented in this manual may not be feasible, applicable or appropriate because of constraints imposed by project budget, right-of-way, or schedule. However, the impacts of a rehabilitation project, whether safety or maintenance projects, must be considered and evaluated. Such projects, for instance may cause changes to the flood surface profile, stream stability, or increase flood risk to neighboring properties. In determining whether a variance from standards and criteria is appropriate, an assessment of the risk involved should be undertaken, as discussed in the next section. The complete replacement of an existing structure that has exhibited no history of past problems must be justified by a compelling reason; simply that it does not meet current hydraulic criteria for new design is not sufficient.