As used in §§ 1803 to 1806 of this title, “right-of-way” means that roadbed of a line of railroad, not exceeding 100 feet in width, as measured horizontally at the elevation of the base of the rail, including the far embankment or excavated area, with slopes, slope ditches, retaining walls or foundations necessary to provide a width not to exceed 100 feet at the base of rail, including tracks, appurtenances, ballast and any structures or building erected thereon.