Preparing considering of economies of scale and adjacent infrastructure works in water main renewal planning

Optimal strategies for scheduling rehabilitation and/or replacement of water mains can generally be classified as high-level planning of groups or cohorts of pipes, or low-level scheduling of individual water mains, which is the subject of this paper. An approach is proposed for the efficient scheduling of replacement of individual water mains. The approach receives as input the expected number of breaks forecasted for each pipe in a short to medium planning period. The present value (PV) of all costs that are associated with each individual pipe is computed and good candidate pipes for replacement within the planning period are identified. Candidate replacement policies are formulated, including economies of scale considerations as well as coordination with other known infrastructure works. A multi-objective genetic algorithm scheme is used as a tool to search a vast combinatorial solution space for feasible solutions that minimise PV of cost as well as maximise usage of available budgets. Various budget scenarios can also be considered, including global budget for the planning period as well as series of annual budgets for each year in the planning period.