A major challenge for society in the 21st century will be replacement, design and optimal management of urban infrastructure. It is estimated that the current world wide demand for infrastructure investment is approximately three trillion US dollars annually. Many developing countries are experiencing rapid growth, and developed countries are facing the need to replace old and obsolete infrastructure to meet existing and future requirements.

Sustaining and expanding infrastructure has traditionally been viewed as related to the need for maintaining economic stability or for providing the basis for sustaining economic growth. However, infrastructure also has a major role in enhancing environmental quality and protecting public health. There is a need to reassess some of our assumptions concerning the way infrastructure is designed, built, utilised, maintained and renewed if we are to satisfy both the economic needs of communities while fulfilling environmental and public health objectives.

Problems associated with ageing drinking water systems in the USA and their difficulty in complying with the increasingly stringent requirements of the Safe Drinking Water Act provide an excellent example of this difficulty.

Starting in September 1993 and lasting through to July 1996, the Washington, DC water supply system experienced a series of microbial violations under the Total Coliform Rule, which is part of the US Safe Drinking Water Act. The US Environmental Protection Agency assigned a team of Agency experts to work with the Washington, DC system to assess the problem and to make recommendations to bring it into compliance. The team suggested 26 major changes, including a US$200m capital investment programme, the development of a hydraulic and water quality model for the system, and a systematic flushing and valve turning programme. In addition, the DC government established a semi-autonomous water utility to operate the system. No new problems were experienced after the programme was initiated.

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