50 C.F.R. § 84.49
All requests for additional monies for approved coastal wetland grants will be subject to the entire review process along with new grants. Any monies left over after the project is complete, or if the project is not completed, should be returned to Headquarters for use in following years. If a State has lands it wishes to acquire, restore, or enhance in close proximity to the original project, and the Region deems that spending project monies in these areas would provide similar benefits, the Region may use unspent balances to pay for these projects with prior approval from Headquarters. States must provide adequate justification and documentation to the Regions that the lands acquired, restored, or enhanced are similar to those in the original proposal and provide similar benefits to fish and wildlife.
50 C.F.R. §84.49