20.—(1) The specified work shall be constructed and in the case of any temporary work removed, in accordance with the plans approved, or deemed to have been approved under paragraph 19 or settled by arbitration, as the same may be amended from time to time by agreement between Network Rail and the undertaker, and in the construction or removal of any specified work Network Rail shall comply with all reasonable requirements of the undertaker and shall provide new, altered or substituted sewers or works for the protection of any sewers of the undertaker, in such manner as the undertaker may reasonably require by way of replacement provision for or for the proper protection of, and for preventing injury or impediment to, any such sewer by reason of any specified work.
(2) All works under sub-paragraph (1) for the provision of new, altered or substituted sewers or the protection of any sewers of the undertaker shall, where so required by the undertaker, be constructed by the undertaker or under the supervision (if given) of an officer of the undertaker duly appointed for the purpose, and all costs, charges and expenses reasonably incurred by the undertaker in the construction of such works, or in the preparation or examination of plans or designs for such works, or in such supervision, shall be paid to the undertaker by Network Rail.
(3) When works for the provision of any such new, altered or substituted sewer, or any such protective work forming part of any such new, altered or substituted sewer or any existing sewer of the undertaker, have been completed under this Part of this Schedule to the reasonable satisfaction of the undertaker, they shall be vested in and become maintainable by the undertaker.