The impact of sewer condition on the performance of sewer systems

Sewer systems are underground infrastructure networks, comprising pipes, manholes and ancillary works, that collect and transport rainfall runoff and sewage to wastewater treatment plants. These systems protect society from exposure to faecal contamination and flooding of urban areas due to heavy storm events to a predefined service level. Protection of the environment (surface water and groundwater) is a main prerequisite as well. Due to deterioration the performance of sewer systems may decrease over time. Consequently, it is important to maintain the defined service level over time. General activities to achieve this goal are sewer cleaning, sewer replacement and the prioritization of strategies. In the Netherlands, 1,5 billion euro is spent annually to maintain and operate sewer systems. Increasingly, risk-based sewer asset management is being advocated to balance the required budget and the provided service to society. A prerequisite for riskbased sewer asset management is to be able to relate the condition of the infrastructure with infrastructure performance and consequently, the provided service level...