Improving the productivity of drainage operations activities through schedule optimisation

Abstract

Operational maintenance of a wastewater collection system involves various activities such as visual inspection, low-pressure flushing, high-pressure flushing, catch basin cleaning, CCTV inspection, and hydromechanized cleaning. These activities are performed at regular intervals at prescheduled locations across the city, which results in a large amount of travel time for the crews performing these activities. Moreover, the stochastic nature of the on-site activity durations leads to unused time at the end of work shifts. A review of the literature and current industry practice reveals the need for schedule optimisation models that specifically address these issues. This research thus formulates the scheduling of drainage operations activities as a special class of combinatorial optimisation problem, and proposes an efficient algorithm to reduce the aforementioned travel and unused times. The model is applied to a monthly high pressure flushing schedule at the City of Edmonton, Canada, showing significant improvement in productivity.