Overview
The risk associated with replacing infrastructure can be quantified in monetary terms by the product of the Probability of Failure and the Consequence of Failure. Intervention to replace infrastructure before failure, reduces risk, but finding usable statistical information to perform such an analysis is difficult.
GLS decided to perform an analysis based on fundamentally independent factors to assess the pipe replacement potential (PRP) for any one modelled pipe in the water distribution model by combining four critical factors:
- Likelihood of failure (LF)
- Consequence of failure (CF)
Various independent variables contribute to each of these factors using a simplified scoring system from 1 to 5 out of 5 (Fi). The information required to determine these variables are available if comprehensive and integrated management information systems have been adopted by the authorities.
The contributing variables are then summated using different weights (Qi) to give total LF and CF factors. The total Pipe Replacement Potential (PRP) is then calculated for each pipe as the product of these factors which is then ranked for all pipes in the model to give the PRP% (in the range of 0 to 100%).
In addition the actual replacement cost for every pipe is calculated. The pipes with high PRP or PRP% can then be visualized graphically. The pipes can be aggregated in various ways to provide the weighted average, maximum or minimum PRP for various collections, such as per suburb or reservoir zone.
For more information see the following poster.
