25 CFR 170.470 - What are the IRR construction standards?
(a) Appendix B to this subpart lists design standards that may be used for roads and bridges.
(1) Tribes may propose road and highway bridge construction standards that are consistent with or exceed these standards.
(2) BIA may also use FHWA-approved, State or tribal road and highway bridge construction standards.
(b) For designing and building eligible intermodal projects funded by the IRR Program, tribes must use either:
(1) Nationally recognized standards for comparable projects; or
(2) Tribally adopted standards that meet or exceed nationally recognized standards for comparable projects.