Reduces excavation work on municipal streets

Have you noticed that the same stretches of municipal roads or bicycle and pedestrian paths are dug up over and over again? One reason may be a lack of coordination between the actors responsible for different parts of the street infrastructure. Researchers at Luleå University of Technology have now developed a model for effective coordination at a time when Sweden is facing historically large maintenance needs for its aging water and wastewater networks.

“With our model, municipal operators can optimize maintenance and renewal efforts in the street environment. This reduces costs for the actors involved, carbon emissions from street work, and perhaps most importantly, traffic disruptions for the public,” says Youen Pericault, researcher in water and wastewater engineering at Luleå University of Technology, who recently defended his doctoral thesis on the topic.

Sweden’s drinking water and wastewater networks face major challenges due to deferred maintenance, population growth, climate change, and stricter environmental requirements. During the Million Programme era (1965–1975), the largest housing initiative in Swedish history, vast networks of water, sewer, and stormwater pipes were installed, networks that now require extensive maintenance. During that period, water pipes made of ductile iron without corrosion protection were commonly used. Pipes from the 1930s, 40s, and 50s will also soon need replacement. These major maintenance needs affect most municipalities in Sweden as well as suburbs of the major cities. For individual municipalities, the costs amount to several billions of SEK.

The network of municipal water and wastewater pipes lies beneath our pedestrian, bicycle, and vehicle roads, which must be excavated when pipes are replaced. By coordinating maintenance between actors responsible for different parts of municipal infrastructure, costs, environmental impact, and public disruption can be reduced. Municipal actors are well aware that coordinating plans for renewing water, heating, and road infrastructure can be beneficial, but achieving such coordination is difficult. One obstacle is that, until now, no effective modeling tool has existed to estimate how a given coordination strategy affects long-term infrastructure renewal costs.

Youen Pericault has developed a method that facilitates long-term collaboration between actors involved in infrastructure renewal. The method is based, in simplified terms, on the concept of a coordination window. This indicates the time frame within which it is cost‑effective to bring forward plans to replace a water pipe or road structure in order to coordinate excavation and paving work and share establishment costs with other infrastructure owners along the same road segment. In this way, water pipes, sewer pipes, and the road can all be renewed in a single reconstruction project. Pericault’s model makes it possible to identify the optimal coordination window based on the age of the infrastructure and local costs for rebuilding pipes and roads.

To demonstrate the method’s usefulness and to investigate optimal levels of coordination, Pericault applied the method in Luleå Municipality, and the results can be applied to many municipalities in Sweden. A coordination window of 15 years was shown to reduce reinvestment costs by approximately 15 percent. At the same time, climate impact, measured as global warming potential, was reduced by 14 percent because the same street did not need to be excavated multiple times. This saved materials, transportation, and energy.

“If municipalities conduct coordinated analyses of water, wastewater, and road infrastructure within a shared planning window, say over 15 years, they can identify solutions that save money, reduce climate impact, and simplify life for residents. This societal benefit risks being lost if each department continues to plan without clear strategies for coordinating work with nearby infrastructure,” says Youen Pericault.

The research was funded by Vinnova and Formas. In a new research project, the model will be tested in real-world conditions in four additional municipalities.

• Read more about Youen Pericault’s research in the dissertation: Coordinated Management of Urban Water Pipe Networks: Co-location and Strategic Rehabilitation Planning with Other Infrastructure.