Resolution No. 4814 - Laserfiche WebLink

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major difference arises, however, because of the networked nature of utilities. As a simple example, consider an electric utility which suffers damage to 10% of its transmission lines. The extent of service outage might be essentially zero if there are redundant lines with sufficient capacity to handle the demand for eiectdc power. Or, the extent of service outage might be 100% if the damaged lines provide the sole power feed for a community. Thus, the operating characteristics and network characteristics (especially the amount of redundancy) must be considered. in conducting risk assessments or evaluating hazard mitigation projects for utility systems, the networked nature of such systems must be considered. The extent or lack of redundancy for particular elements in a system profoundly affects the extent to which a given level of damage results in system outages. The general procedure for conducting a risk assessment or evaluating a hazard mitigation project for a networked utility system is outlined below in six steps. 1) Overlay utility system components with hazard maps, 2) Estimate the vulnerability of each component to effects from each hazard, 3) From the estimated amount of damage to the system and the system's network operating characteristics, estimate the extent and duration of service outage, 4) From the damage estimates and the resources available, estimate the restoration time, 5) From the service outage (number of customers and duration) estimate the economic impacts of such loss of service, and 6) If a mitigation project is being evaluated estimate the reduction in direct damages and the reduction in service interruption attributable to mitigation project. An important caveat for conducting risk assessments or evaluation of hazard mitigation projects for networked utility systems is that specialized expertise is often required. The analyst must thoroughly understand the operating characteristics of utility system components and their vulnerability to each hazard as well as thoroughly understand the network operating characteristics of the system as a whole. In the absence of sufficient experience and expertise risk assessments or evaluation of hazard mitigation projects may produce inaccurate and misleading results. CAVEAT: conducting risk assessments or evaluation of hazard mitigation projects of networked utility systems often requires specialized expertise to produce meaningful results. For reference, a detailed discussion of how to evaluate seismic hazard mitigation projects for water systems is given in the American Society of Civil Engineers monograph "Guide#nos for the Seismic Upgrade of Existing Water Transmission Public Review Draft: August 6, 2004 13-4