Würzburg, 12 January 2022 – SPIE, the independent European leader in multi-technical services in the areas of energy and communications, deployed its experts from SPIE OSMO to fit out the tunnel and its entry points with operational and traffic engineering. Heidingsfeld and Heuchelhof, two suburbs of Würzburg, were divided by the busy A3 motorway for a long time but have now been re-united by a public green space. This has been made possible by the new Katzenberg Tunnel.
Tunnel links Würzburg suburbs
The A3 motorway, one of the key transport routes through southern Germany, runs directly through the environs of Würzburg and, before it was modified, cut the suburbs of Heidingsfeld and Heuchelhof off from one another. Those in charge therefore decided that the upgrade to the A3 presented an opportunity to implement a modern approach to urban planning, burying a 570-metre section of the motorway in a tunnel – the Katzenberg Tunnel – to allow the suburbs to grow closer together again. Once the public green space above the tunnel is complete, the ecological links between the suburbs will be restored, having previously been severed. The tunnel will also help to reduce noise in Würzburg. The order was placed in 2015 by the Autobahndirektion Nordbayern motorway authority, which has since had its remit taken over by the northern Bavarian branch of the newly established Autobahn GmbH, a company operated by the federal government.
State-of-the-art tunnel fit-out and traffic engineering
The experts from SPIE OSMO, the unit of SPIE Deutschland & Zentraleuropa carrying out the work, fitted the Katzenberg Tunnel out with the complete package of operational tunnel equipment and traffic engineering. That also included the entry points at Heidingsfeld at the western end, where a bridge over the valley, also recently replaced, leads directly into the Katzenberg Tunnel, and the Würzburg service station by the eastern portal of the tunnel. Both sites are also equipped with automated road signs, barriers and video surveillance, enabling the flow of traffic to be halted in the event of an incident in the tunnel.
A3 motorway kept open to traffic throughout the project
One particular challenge facing the SPIE OSMO project team was to work on technical implementation for a motorway that had to remain open to large volumes of traffic throughout the entire project. That was why it was such a protracted undertaking, lasting from 2015 to 2021. In the first phase, the contractor responsible for erecting the operations building and the Frankfurt-bound tunnel bore slightly below the existing motorway route. After the necessary functional testing, traffic flowed in both directions through this new bore, allowing the second tunnel section to be bored at the same level of the previous motorway in the second phase. "One tricky assignment for us came during the second phase, when we had to ensure that traffic could keep running in the first bore while working in the second at the same time" said Falko Weiß, site manager at SPIE OSMO, "but we worked with the client and all the other companies involved and managed to pull it off safely."
The Katzenberg Tunnel, which was built as part of the six-lane upgrade to the A3 motorway, is one of the largest projects that the tunnel experts at SPIE OSMO have worked on. Traffic runs on four lanes towards Frankfurt and three lanes in the opposite direction through the two bores. There is also a hard shoulder and an emergency walkway in each bore. That means that the southern bore is roughly 17 metres wide, and the northern bore is 19 metres wide. ‘The structure gauge by itself made the Katzenberg Tunnel a fascinating and challenging project,’ said Uwe Wollenburg, project manager at SPIE OSMO.
Still operational even in the event of a power cut
To ensure the necessary level of safety for road users, the team from the multi-technical service provider installed 818 tunnel lights, 25 jet fans with an output of 30 kilowatts each, 115 fire and smoke alarms, 2,400 metres of fire alarm cabling, 1,377 emergency and signal lamps and 27 emergency call points. There are 61 cameras giving the traffic and operations control centre for northern Bavaria the ability to keep an eye on the tunnels remotely, while instructions and information can be relayed through 54 speakers.
The power necessary to keep the systems running comes via two medium-voltage transformers, each with output of 1,000 kilovolt-amperes, one set of 20-kilovolt medium-voltage switchgear and, in case of power cuts, an emergency power system with an output of 300 kilovolt-amperes. "The emergency power system, which will keep the tunnel operational if there is ever a power outage, is a special feature of this project", explained Wollenburg. There are 210 variable message signs and seven mechanical barriers linked via 23 sub-control centres. Six computer systems for tunnel and traffic management process approximately 20,000 data points relating to the Katzenberg Tunnel.
A long-term partnership
Now that the Katzenberg Tunnel has been completed, the northern Bavarian branch of Autobahn GmbH is continuing to count on SPIE as a dependable partner for safe and reliable system operation. Service technicians from SPIE have been taking care of the tunnel ever since it was opened to traffic after the first two phases. The maintenance experts will continue to lend their support to the operator over the next five years to ensure that the tunnel remains safe for road users. "We are exceptionally proud to have earned the trust of our customer and had the opportunity to prove our expertise over a long-term project. We are very much looking forward to continuing to work together" said Klaus Eismann, managing director of SPIE OSMO from the Building Technology & Automation operational division at SPIE Deutschland & Zentraleuropa.