Drinking Water Distribution Systems, Chapter 7 – Part Two Report of the Walkerton Inquiry

Threats to a distribution systems integrity include: pipe age, materials, system design, storage, corrosion, scale, sedimentation, biological growth, and bulk water reactions. Click here to read the full chapter or an excerpt below.


7.4 Good Practices in System Operation

A large and rich literature deals with good practices in system operation and maintenance.32 Drawing together much of what has been said above, good practices in system design, operation, and maintenance include the following:

• Design the system so that it is not so large that slow turnover and high retention times degrade water quality.33 Distribution systems can be problematic at either end of the size continuum – they can be too small to accommodate fire emergencies or too large to guarantee safe water. Overbuilding a distribution system (i.e., making it too large) can have consequences for both water quality and cost.34

• Make regular systematic flushing, with particular attention to dead ends and static zones, part of every maintenance program.

• Operate the system at a steady rate (except during emergencies) that allows for treatment optimization and the minimization of DBPs while maintaining the flexibility to cope with unexpected demand.

• Monitor water flow and basic measures of quality (disinfectant residual, turbidity, and pH, at a minimum) throughout the distribution system on a real-time basis, and adjust flows and treatment to match the changing conditions of demand or system integrity in real time.

• Monitor the condition of the distribution system itself, so that the threats to integrity mentioned above can be managed without threats to public health or excessive loss of water35 and so that capital repairs and replacement can be scheduled on a rational basis. Timely repair or rehabilitation can often extend the lifetime of infrastructure at modest cost. “Sustainable asset management,” which was recommended by a number of the parties in Part 2 of this Inquiry, is discussed in Chapter 10 of this report. One consequence of this approach is a capacity to work with other utilities to minimize multiple trenching and traffic detours.

• Maintain the network by continually improving techniques for refitting and replacement. New techniques for horizontal drilling, reaming, and pipe lining are available to extend the life of existing pipes.36

• Ensure that repair and maintenance crews follow industry-accepted sanitary practices when performing any maintenance activities.

• Maintain computerized models of the system that assist with everything from operational control to optimal capital investment.






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