# The Gatwick Airport (Northern Runway Project) Development Consent Order 2025, Paragraph 31: Construction sequencing

Extent: E+W

(1) The commencement of dual runway operations must not take place until Work No. 43 (water treatment works) has been completed.
(2) Work No. 39(b) (River Mole culverts and syphons) must not be commenced until Work No. 42(b) (weir and fish pass) has been completed.
(3) The undertaker must prepare and provide to Thames Water Utilities Limited a development phasing plan which will include forecast passenger growth numbers for the period up to the commencement of dual runway operations and ten years after the commencement of dual runway operations. The development phasing plan must include detailed forecasts of the wastewater discharge rates and expected connection points for the authorised development throughout this period and be based on hydraulic modelling undertaken by Thames Water Utilities Limited or the undertaker in consultation with Thames Water Utilities Limited and validated by Thames Water Utilities Limited in writing.
(4) If the hydraulic modelling is undertaken by the undertaker in consultation with Thames Water Utilities Limited—
(a) Thames Water Utilities Limited will provide a formal review and response within 3 calendar months of receipt of the undertaker’s hydraulic modelling, which will either indicate the results are validated or the steps required to validate the results;
(b) the undertaker will comply with those steps in order to achieve validation of their hydraulic modelling for submission to Thames Water Utilities Limited within a further 3 calendar months; and
(c) Thames Water Utilities Limited will respond to the updated submission within 3 calendar months of receipt.
(5) If, when responding under sub-paragraph (4)(c), Thames Water Utilities Limited concludes that the undertaker has not complied with the steps pursuant to sub-paragraph (4)(b), this question is to be referred to an independent Chartered Engineer (to be agreed between Thames Water Utilities Limited and the undertaker or, if not agreed, to be appointed by the President of the Chartered Institute of Water and Environment Management upon the request of either party). The decision of the Chartered Engineer is binding as to whether the hydraulic modelling is validated for the purpose of sub-paragraph (3).
(6) The details in the development phasing plan provided pursuant to sub-paragraph (3) must not materially exceed the forecast annual passenger numbers shown for the equivalent time periods for the airport with the authorised development in Table 9.2-1 of the forecast data book.
(7) Thames Water Utilities Limited must confirm in writing within twelve months of the provision of the development phasing plan pursuant to sub-paragraph (3) whether its infrastructure will be able to accommodate the additional foul water flows from the airport for the ten-year period after the commencement of dual runway operations.
(8) The commencement of Work No. 44 (wastewater treatment works) must not take place until either—
(a) Thames Water Utilities Limited confirms that its infrastructure will not be able to accommodate the additional foul water flows;
(b) Thames Water Utilities Limited has not provided any confirmation pursuant to sub-paragraph (7) within the time period specified therein; or
(c) Thames Water Utilities Limited has not responded pursuant to sub-paragraph (4)(a) or (4)(c) within the time period specified therein,
unless otherwise agreed in writing by Thames Water Utilities Limited.
(9) The commencement of dual runway operations must not take place until either—
(a) Work No. 44 (wastewater treatment works) has been completed, and an application has been submitted for an environmental permit under regulation 12(1)(b) (requirement for an environmental permit) of the Environmental Permitting (England and Wales) Regulations 2016 for its operation; or
(b) Thames Water Utilities Limited confirms that its infrastructure will be able to accommodate the additional foul water flows.
unless otherwise agreed in writing by Thames Water Utilities Limited.

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Source: https://www.legislation.gov.uk/uksi/2025/1054/schedule/2/paragraph/31 (the official version)
Page: https://openlegislation.uk/gatwick-airport-northern-runway-project-development-consent-order-2025/schedule-2/paragraph-31
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.