Detailed description of water supply and waste water management networks

Local authorities and their partners must provide detailed specifications for their drinking water supply system and their waste water management system.

This is no easy task for local authorities, as they face the following key problems:

• Insufficient knowledge of the network
• Ageing equipment and amenities
• Lack of resources and personnel
• Safety issues for staff and equipment

NETWORK KNOWLEDGE

Specifications are expected to include:

• A network map identifying the location of the general water meters
• A network inventory which comprises:
  • a diagram of the pipelines
  • the year or, failing that, the decade in which the pipelines were laid
  • the category of the system in terms of the new legislation relating to work projects undertaken in proximity to networks
  • cartographic information
  • type of materials used for the pipelines and their diameter.

The specifications must be compiled and updated every year, indicating any work carried out on the network and data collected during the year.

NETWORK PERFORMANCE

As well as providing these inventories, local authorities are required to ensure that the pipelines are kept in good condition. According to environmental laws, if the network’s yield falls below a certain threshold, the public services responsible for water distribution must implement an action plan before the end of the following term.

NETWORK MAINTENANCE PLANNING

In particular, the action plan involves an annual follow-up check regarding network yield and, where applicable, a programme to implement a series of network improvements over several years.

In accordance with the action plan, the detailed specification for the drinking water supply network should be kept up-to-date, identifying the sections that have been subject to water loss inspections and any subsequent repairs carried out.

DRINKING WATER SUPPLY SYSTEM FIGURES

• Total length of pipeline : 906,000 km (France)
• Annual water production : 6 billion per m3
• Network water loss : 24%
• Amount of network built before 1972 : 50%
• Rate of pipeline renewal currently in place : 6%/year

which means all the pipelines will be replaced after : 170 years

• Lifespan of pipeline : 60 to 80 years

The above figures highlight the need to maintain and renew the water pipeline network in France, both for economic and environmental reasons. Furthermore, the longer it takes to make this investment, the higher the eventual cost is likely to be for future generations.

Based on the inventory, a more ambitious renewal project must be put in place – one that corresponds with the lifespan of the networks. According to industry observers, the average national rate of renewal should be more along the line of 1.25% per year.

WATER NETWORK RENEWAL AS PART OF A SUSTAINABLE DEVELOPMENT PROGRAMME

Recent French legislation has set in motion a move towards sustainable management of the pipe network estate. The required inventory includes elements that are essential for determining a hierarchy of investment for network repairs and renewals.

It only takes a few numbers to understand the reality of the situation and the urgent need to invest in the rehabilitation of the water networks. Of the 906,000 km of drinking water supply pipes, 50% date back to before 1972. The four pipe materials – steel, galvanised iron, PVC and asbestos cement – are the cause of breakages and leaks, and account for around 60% of the estate that needs replacing. Leaks may equally have been caused by damage to the land where the pipes are located, for example sinking or vibrations.

According to the latest Water and Sanitation survey by the Department of Ecology, the network extension is progressing at a rate of 3,750 km per year, whereas network renewals were only 5,041 km per year. At the current rate of investment, it will take nearly two centuries to replace the pipelines. This means that a drinking water supply pipeline will not be replaced for 170 years (906,000 km per year divided by 5,041km), although its estimated lifespan is just 50 to 60 years, depending on the type of pipe. The average renewal rate is therefore 0.6% per year. Economies achieved by reducing water leaks could allow for the renewal of an additional 1,500 to 6,000 km of network.