Notwithstanding the joint resolution entitled “Joint resolution providing for the construction and maintenance of a National Gallery of Art”, approved March 24, 1937 (50 Stat. 51; 20 U.S.C. § 71 ), the Mayor of the District of Columbia is authorized to use the east 65 feet of the area bounded by 4th Street, Pennsylvania Avenue, 3rd Street, and North Mall Drive Northwest, in the District of Columbia for the construction and maintenance of a vehicular tunnel, on condition that after such construction is completed:
(1) The surface thereof is maintained at its original grade;
(2) No portion of the tunnel, including ventilating equipment and utilities, is nearer the surface than 8 feet; and
(3) The surface ingress and egress to such property is not limited.