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WERF: Sewer Inspection Prioritization Using an Expert System
Author: M. Steve Merrill, Andrew B. Lukas, Margaret A. Hahn, Richard N. Palmer
Date: 10/00
Presented at WEFTEC 2000 in Anaheim, CA.

The sewer infrastructure of the US must be assessed and upgraded to meet the requirements of the EPA Sanitary Sewer Overflow Policy and the guidelines of the Government Accounting Standards Board Statement 34. Traditionally, age, size and material (brick and other pipe materials) have been the only factors used in prioritizing inspections and in predicting the timing of potential repair and replacement. This traditional approach is not sufficient and does not take into account a deeper understanding of the variables leading to structural or operational failure, or of the impact of failures on the community and the environment. All utilities face budget constraints that limit the ability to inspect and repair or replace sewer infrastructure. Smaller utilities may have little information about their infrastructure. A method is needed to prioritize the acquisition of information with which the sewers can be assessed and rehabilitation programs and budgets developed. The Water Environment Foundation contracted with Brown and Caldwell to develop a tool to help utilities prioritize inspection of sewers to overcome these constraints. The tool is based on an expert system developed by the University of Washington authors. The tools knowledge base was assembled from a group of national experts. Input from these experts was used to develop the tools logic assessing the need to inspect specific lines based on available information. In validation exercises using case studies supplied by the experts, the tool was shown to outperform a group of experts in quantifying the need to inspect.