Whenever the board has acquired or shall in the future acquire title in fee to any land in the name and in behalf of the district and whenever, in the judgment of the board, the purposes of the district will be satisfied by the retention of an easement or other interest in the land less than the title in fee thereto, the board shall take all steps necessary to sell said land reserving to said district the easement or other interest acquired for the purposes of the district. Conveyances of such land or interest therein owned by the district shall be executed by the officers of the board authorized by the board and shall be approved by the Director of General Services.