Identification of the optimal level of service for sewer networks by means of expert procedure

This work presents the application of a knowledge base for an expert system that predicts the criticality of sewer pipe-lines. The, SCRAPS model (Sewer Cataloging, Retrieval and Prioritisation System), developed by Hahn (2000) considers information about the state of a sewer network through an extensive set of relationships that describe failure impact mechanisms. The SCRAPS has been applied to a part of the sewer system of Pesaro (Italy) managed from ASPES S.p.A. With the SCRAPS software, combined with EPA SWMM for the simulation of hydraulic aspects, have been analysed the actual state of the sewer system estimating the various degrees of necessity of inspection of the various conduits. The simulations carried out have been allowed to identify the Level of Service corresponding at the minimum management cost supposing that the investment plan is equal to 20 years, resulting equal to the 20%, where the Level of Service is the difference between 100 and the value of Need of Inspection.