Marshall, Morley, Pearson
Renovation & Rehabilitation # 1998 Gothenburg
The Water Industry in England and Wales has responsibility for an approximate length of 300,000km of water main, ~nuchof which was laid over 70 years ago using cast iron.
Subsequently, asbestos cement, PVCu and cement lined ductile iron have been used. The old iron pipe systems that were installed in many of the world's great conurbations between 1870 and 1930 are now nearing the end of their useful life. The cost of renovation is enormous and in situations where burst frequency and modest leakage are 'tolerable'. criteria to assist in the decision as to whether to repair mains or alternatively consider wholesale replacement are needed.
The decision to re-line a pipe or use 110-dig tecllniques to rehabilitate the system with new pipes capable of withstanding all structural loadings depends not only on the present burst frequency but also on the predicted lifetime that remains. It makes no sense to line pipes in wliich corrosion is so advanced that a cement Inortar lining will offer little benefit as regards extending the life. To expend far greater sums to structurally line pipes that have suffered little deterioration, also makes no economic sense.
During the last eight years, the UK water companies have spent large sums of money on pipe systems (approximately £600 million per year) in a drive to improve water quality. It would be wise to use this experience as a basis for a common approacli towards renovation choice.
Historically, there has not been one nationally agreed procedure, but a mixture of options and approaches that are suited to the different needs of different companies.
However, there is noN a developing beliel'that the structural condition of the pipework. plus factors affecting leakage. liydraulic performance and water quality need to be combined in an 'holistic' approach towards the renovation problem.