Risk-based prioritisation of inspections and rehabilitation of wastewater pipes

Journal article, 2026

Reinvestments in wastewater pipe networks pose financial challenges due to high costs in combination with the complexity of rehabilitation prioritisation. Lack of pipe data and unknown pipe conditions are some factors contributing to the complexity. In Sweden, many of the wastewater pipe networks were constructed in the 1960s and 1970s and are now approaching the end of their technical life. With large investments anticipated in the coming decades, water utilities have the potential to reduce costs by identifying and prioritising high-risk wastewater pipes for rehabilitation. In this study, a risk-based decision model is presented to facilitate the strategic rehabilitation of wastewater pipe networks. The model is based on a two-tiered approach: the first tier identifies high-priority pipes for Closed-Circuit Television (CCTV) inspections, while the second tier utilises the CCTV-inspection results to estimate the probability of failure and update the risk assessment. A multi-criteria decision analysis model was utilised to prioritise wastewater pipe rehabilitation as well as CCTV-re-inspections. Hence, the model represents a novel integration of local CCTV-grades when establishing re-inspection frequencies and prioritisation of wastewater pipe rehabilitation prioritisation. Within six months, the model was implemented in the wastewater pipe network in Kungsbacka municipality, Sweden. The model enabled the development of an inspection plan and rehabilitation prioritisation, representing a significant step towards cost-effective and efficient wastewater pipe network management.