Notwithstanding any other provision of law, every public utility district acquiring privately owned lands, real estate or property for reservoir purposes of a hydroelectric power project dam on the Columbia river, upon acquisition of title to said lands, whether acquired by purchase or condemnation, shall grant back to the former owners of the lands acquired upon their request therefor, whether prior to conveyance of title to the district or within sixty days thereafter, a perpetual easement appurtenant to the adjoining property for such occupancy and use and improvement of the acquired lands as will not be detrimental to the operation of the hydroelectric project and not be in violation of the required conditions of the district's federal power commission license for the project: PROVIDED, That said former owners shall not thereafter erect any structure or make any extensive physical change thereon except under a permit issued by the public utility district: PROVIDED FURTHER, That said easement shall include a provision that any shorelands thereunder shall be open to the public, and shall be subject to cancellation upon sixty days notice to the owners by the district that such lands are to be conveyed to another public agency for game or game fish purposes or public recreational use, in which event the owners shall remove any structures they may have erected thereon within a reasonable time without cost to the district. The provisions of this section shall not be applicable with respect to: (1) lands acquired from an owner who does not desire an easement for such occupancy and use; (2) lands acquired from an owner where the entire estate has been acquired; (3) lands acquired for, and reasonably necessary for, project structures (including borrow areas) or for relocation of roads, highways, railroads, other utilities or railroad industrial sites; and (4) lands heretofore acquired or disposed of by sale or lease by a public utility district for whatsoever purpose.