In order to facilitate the administration of Zion National Park and Yosemite National Park, the Secretary of the Interior is authorized, under such terms and conditions as he may deem advisable, to expend donated or appropriated funds for transportation systems or for the establishment of essential facilities for park administration and visitor use outside the boundaries, but within the vicinity, of the park. Such systems or facilities and the use thereof shall be in conformity with approved plans for the park. The Secretary shall use existing facilities wherever feasible. Such facilities may only be constructed by the Secretary upon a finding that the location of such facilities would—