Environmental and structural risk assessment of long operated vitrified clay sewers

Investigations have been presented on the type, extent and frequency of operational and maintenance as well as structural linear and spot defects that occurred in long operated vitrified clay sewers, which are the most often used in sanitary sewer systems. The causes of the defects have been deter-mined and summarized in five groups. Two sewer failure probability matrices taking into account the impact of all the defects analysed in terms of environmental and structural hazards have been proposed. Numerical values determined for each element of the two matrices allow allocating the sewers into five probability of failure categories. The proposed method contains the consequences of failure of matrix of sewer, and finally two matrices of risk for environmental and structural safety. The elaborated method enables prioritization of sewers in terms of environmental and structural hazards from those of the highest to those of the lower risk, which allows efficient sewer failure management and may be used for planning the sewer trenchless maintenance and rehabilitation.