9If any pile, stump or other obstruction becomes exposed in consequence of a tidal work (other than a pile, stump or other obstruction situated on the site of any permanent work) the Secretary of State shall, as soon as reasonably practicable after the receipt of notice in writing from the Port Authority requiring such action, remove it from the river or, if it is not reasonably practicable to remove it, cut it off at such level below the bed of the river as the Port Authority may reasonably direct.