(10) The powers conferred on the undertaker by this article with respect to any road have effect  subject to any agreement entered into by the undertaker with any person with an interest in (or  who undertakes activities in relation to) premises served by the road.  (11) If the traffic authority fails to notify the undertaker of its decision within 28 days of  receiving an application for consent under paragraph (2) the traffic authority is deemed to have  granted consent.  17. —(1) Subject to paragraphs (3) and (4), the undertaker may use any watercourse or any  public sewer or drain for the drainage of water in connection with the carrying out or maintenance  of the authorised development and for that purpose may lay down, take up and alter pipes and  may, on any land within the Order limits, make openings into, and connections with, the  watercourse, public sewer or drain.  (2) Any dispute arising from the making of connections to or the use of a public sewer or drain  by the undertaker under paragraph (1) is to be determined as if it were a dispute under section  106( a ) (right to communicate with public sewers) of the Water Industry Act 1991.  (3) The undertaker must not discharge any water into any watercourse, public sewer or drain  except with the consent of the person to whom it belongs; and such consent may be given subject  to such terms and conditions as that person may reasonably impose, but must not be unreasonably  withheld.  (4) The undertaker must not make any opening into any public sewer or drain except—  (5) Save where permitted by this Order, the undertaker must not, in carrying out or maintaining  works under this article, damage or interfere with the bed or banks of any watercourse forming  part of a main river.  (6) The undertaker must take such steps as are reasonably practicable to secure that any water  discharged into a watercourse or public sewer or drain pursuant to this article is as free as may be  practicable from gravel, soil or other solid substance, oil or matter in suspension.  (7) Nothing in this article overrides the requirement for an environmental permit under  regulation 12(1)(b) (requirement for environmental permit) of the Environmental Permitting  (England and Wales) Regulations 2016( b ).  (8) In this article—  (9) If a person who receives an application for consent under paragraph (3) or approval under  paragraph (4)(a) fails to notify the undertaker of a decision within 28 days of receiving an  ( a ) 1991 c. 56. Section 106 was amended by sections 35(1) and (8), 43(2) and 56I(7) of, and Schedule 2 to, the Competition  and Service (Utilities) Act 1992 (c. 43), sections 36(2) and 99 of the Water Act 2003 (c. 37) and section 32 of, and  paragraph 16(1) of Schedule 3 to the Flood and Water Management Act 2010 (c. 29).  ( b ) S.I. 2016/1154. Regulation 12 was amended by 2018/110.  ( c )  1991 c. 57.  16 (b) other expressions, excluding watercourse, used both in this article and in the Water  Resources Act 1991( c ) have the same meaning as in that Act.  (a) “public sewer or drain” means a sewer or drain which belongs to Homes England, the  Environment Agency, an internal drainage board, a joint planning board, a local  authority, a sewerage undertaker or an urban development corporation; and  (b) where that person has been given the opportunity to supervise the making of the opening.  (a) in accordance with plans approved by the person to whom the sewer or drain belongs, but  such approval must not be unreasonably withheld; and  PART 4  SUPPLEMENTAL POWERS  Discharge of water 