“ Exchange.—The term ‘‘exchange’’ means the exchange of land authorized by section 3 (a) . Sec. 3. Land Exchange. (a) In General.—Subject to subsection (d) , the Secretary may exchange approximately 20 acres of land within the boundary of the Blue Ridge Parkway that are generally depicted on the map as ‘‘Blowing Rock Reservoir’’, for approximately 192 acres of land owned by the Town that are generally depicted on the map as ‘‘Town of Blowing Rock Exchange Lands’’. ”