Model Consultative Procedure for Pipeline Construction involving Deep Excavation
January 1993


  1. This document sets out a procedure to provide a consistent approach to avoiding problems with the underground pipeline assets of the water, sewerage and gas undertakers when trenching works are carried out.

  2. Trenching activities were highlighted by the King Inquiry1 in 1977 as one source of ground movement responsible for the fracture of grey iron gas pipes. This was confirmed by subsequent studies of fracture records and extensive research culminating in a damage control agreement between British Gas and the National Water Council in 1982, and effective from 1st January 1983. The procedure and its revisions were formally applied until November 1990.
    This document represents a major revision of the old procedure based on more recent data and improved analysis techniques.

    The new procedure differs from the old procedure in the following

  3. The document relates to consultation between water or sewerage undertakers or their agents and the appropriate region of British Gas whenever trenching works are proposed by either party. Emergency works are excluded.

  4. The procedure is intended to be reciprocal between the undertakers.

  5. This damage control procedure deals with the notification, design and execution of trenching works so as to minimise the risk of damage to grey iron mains and reduce the cost and inconvenience to all concerned.

    Deep excavation in the vicinity of asbestos cement and clayware pipes is outside the scope of the procedure. In the event or such excavation, special arrangements shall be negotiated locally within the spirit of the agreement.

  6. The procedure is intended to supplement but not to amend, abridge or override any provisions in respect of street works under Acts of Parliament, and to operate within the framework of statute and common law governing the activities of both industries.

    The document also supplements the British Gas Engineering Standard PS/G10
  7. Regular consultation and the application of the acceptable proximity criteria should allow problems to be identified and resolved at an early stage, to achieve a least cost solution.

  8. Should difficulties arise the matter should be resolved whenever possible by local agreement.

  9. The technical content of this document has been formulated by the British Gas Engineering Research Station and appraised by the Water Research Centre. Situations outside the scope of this document do not necessarily represent acceptable conditions.
1 King, P. J., Clegg, G. T. and Walters, W. J. Report of the Inquiry into serious gas explosions. Department of Energy, HMSO. June 1977.
Copies of this report are available from the Foundation, price £30.00 less 20% for FWR members