For the construction of a 14-kilometre waste water drainage tunnel in the Swedish capital, Axians designed an innovative “network” solution to ensure total operational safety throughout the works’ duration.

Over the last 20 years, the population of Stockholm has grown from less than 750,000 to more than a million. During the same period, the population of the whole metropolitan area rose from 1.7 to 2.4 million. This strong demographic growth has naturally brought a substantial increase in water consumption and consequently in the need for waste water treatment.

“We were appointed as prime contractor for the ‘network’ system, which makes it possible to pinpoint every worker’s exact location on site.”

To increase its capacity in this area, the city decided to expand the Henriksdal water treatment plant, situated south-east of the city, with the aim of making it one of the most modern plants in the world.

At the same time, the Bromma treatment plant located west of the city will be closed. Waste water from Västerort (West Stockholm), currently treated at Bromma, will be transported through a new 14-kilometre tunnel to the treatment plants at Sickla and Henriksdal.

The latter’s increased capacity will help to maintain water levels in Lake Mälaren to the west, and to reduce discharges into the Baltic Sea to the east, while avoiding the transportation of sewage sludge through residential areas.

Locating all on-site personnel in real time

The construction of this long tunnel was entrusted to the firms Veidekke and YIT, which began work early in 2020 with completion scheduled for 2026, and required the implementation of a system to ensure safe working, including monitoring of all entries and exits to and from the worksite.

As Thomas Jansson, Market Manager at Axians, the VINCI Energies ICT brand, explains, “With the assistance of Eitech (VINCI Energies), who helped us during the call for tender to make contact with the right partners to get the project done, we were appointed as prime contractor for the ‘network’ system, which makes it possible to pinpoint every worker’s exact location on site.”

For safety reasons, it is essential to be aware and keep track of all personnel and vehicles on site, in case of emergency. Axians is working on this brief with the Swedish firms Mobilaris, which manages the software, and TPO, which designed and provided the equipment.

Safety system based on Wi-Fi

The project required the implementation of a safety system based on Wi-Fi, equipped with VoIP communications for the tunnels, an evacuation alarm, a tunnel access control system and an internet connection for the working tools.

“The bulk of the work will be completed in the first year, setting up the Wi-Fi network and all the installations in the connecting tunnels. Then we’ll proceed with the continuous installation of the Wi-Fi network in the main tunnel as it progresses,” says Thomas Jansson. The finished system will include a central network, 70 PoPs (points of presence) in the form of network interfaces, 350 APs (Wi-Fi access points) and 5 access control locations.