# 2004 Milan
In 1999 the Health & Safety Executive agreed to the introduction of a new risk based methodology to be used for prioritising iron mains replacement. The introduction of this methodology combined with the results of major incident investigations has led the Health & Safety Executive to conclude that the potential risk of failure of medium pressure ductile iron pipes located within 30 metres of buildings is such that their replacement should be carried out as soon as possible. The findings affect all owners and operators of gas distribution systems but none more so than Transco, a company divested from the former British Gas, which owns virtually all of the iron pipes laid across the United Kingdom. Following consultation and agreement between the Health & Safety Executive and Transco, an enforcement notice was issued which required Transco to replace 2300 kilometres of ductile iron pipe over a 24 month period ending in December 2002. The background to this process is described in some detail together with the decision to adopt multilayer polyethylene pipe systems as the modern solution for the transportation of natural gas in the United Kingdom.