Notwithstanding the foregoing, however, the Secretary shall omit from the park sections
7 and
17, P.S.L. Block 121, in Hudspeth County, and revise the boundaries of the park accordingly if the owner of said sections agrees, on behalf of himself, his heirs and assigns that there will not be erected thereon any structure which, in the judgment of the Secretary, adversely affects the public use and enjoyment of the park.