15.1 OPERATIONAL NEEDS FOR RESPONDING TO CONTAMINATION EVENTS

The contamination of a drinking water supply, whether accidental or deliberate, can pose serious risks to public health and industries which require a supply of high quality water. An appropriate and effective response is therefore required to minimize these risks while also keeping disruptions to water supplies at a minimum. When a contaminant, chemical or biological, enters the distribution system the operations staff is presented with the challenging tasks of delineating the extent of the contamination spread, isolating the contaminated sections of the network, flushing the contaminant from the affected zones, and bringing the system back to full operations at the end of the event. These tasks are made more difficult by the high level of interconnectivity inherent in typical pipe network layouts and the low level of observability of the distribution system.

Water distribution systems typically are designed with a high level of redundancy, thereby assuring high levels of consumer service. The multiple flow paths created by a highly interconnected network allow a continued supply of water to consumers even when a segment of pipe is isolated. Maintenance and upgrades to the distribution system can then be conducted with minimal impact on consumers. For example, a residential subdivision supplied by a single main connected to the rest of the distribution system is vulnerable to disruptions in supply. The isolation of this main for maintenance would cut off supply to the...