In the case of land specified in the following table, the power conferred by section 6(1), so far as relating to so much of the land as does not lie more than 9 metres beneath the level of its surface, shall be exercisable only in relation to the creation and acquisition of easements or other rights over land for the passage of persons or vehicles (with or without materials, plant and machinery) for the purpose of or in connection with the construction or maintenance of the works authorised by this Act.