The National Culvert Removal, Replacement, and Restoration Grant Program (Culvert Aquatic Organism Passage (AOP) Program) is an annual competitive grant program that awards grants to eligible entities for projects for the replacement, removal, and repair of culverts or weirs that meaningfully improve or restore fish passage for anadromous fish.

Eligible project types include culverts and weirs having a transportation nexus and posing barriers to anadromous fish. With respect to weirs, projects may include infrastructure to facilitate fish passage around or over the weir and weir improvements. A weir is a constructed barrier on a stream channel designed to provide hydraulic control without completely stopping flow or creating a large storage impoundment. A dam is not a weir for the purposes of this program.