Low-cover, heavy-duty sprinkler tank for Norlys HQ, Aalborg

Ultra-low installation height delivers a 60-ton drivable surface with minimal excavation, and a five-hour install 

The Challenge 

For the new Norlys headquarters in Aalborg, Denmark, the project team needed an underground sprinkler water tank beneath areas with very limited build-up height. The solution had to provide a drivable surface capable of carrying heavy traffic loads while keeping excavation depth to a minimum and avoiding complex on-site works. Vertical clearance was the defining constraint, alongside stringent quality and testing requirements for fire protection systems. 

The Solution 

ViaCon engineered, manufactured, and installed a prefabricated corrugated steel sprinkler tank optimized for ultra-low cover without compromising structural capacity. In close collaboration with main contractor and subcontractor, we delivered a DN2400 tank in Z600 galvanized steel with D3 corrugation, verified to support a 60 t traffic load with as little as 0.3 m soil cover. 

Configured for reliability and fast tie-in, the tank includes two Ø250 check valves integrated in sumps, a manhole brought to surface for full inspection access, and DIN-flanged nozzles for rapid PE pipe connections at grade. Quality was assured through factory pressure testing by an independent third party in Mülheim and re-testing on site in accordance with DBI guidelines. 

Installation on site took just five hours: the customer craned the unit directly from the truck into the prepared excavation and our team completed the final fit-out. The minimal build-up height reduced excavation volumes and program time, while the prefabricated approach limited site interfaces and disruption. 

The ViaCon Advantage 

  • Ultra-low cover, high load capacity: 60 t drivable surface with just 0.3 m soil cover. 
  • Fast, low-disruption delivery: Prefabricated unit installed in five hours, minimizing downtime and interface risks. 
  • Assured performance: Independent factory pressure testing and on-site testing per DBI guidelines. 
  • Simple connections and access: DIN-flanged nozzles for quick PE tie-in; manhole to grade for full inspection and maintenance. 
  • Optimized site logistics: Reduced excavation depth and straightforward placement limited spoil, truck movements, and on-site complexity. 
  • Collaborative execution: Close coordination with A. Enggaard A/S and Henning Mortensen A/S ensured a smooth, on-schedule installation. 

Technical specifications 

  • Pipe diameter: DN2400 
  • Corrugation: D3 
  • Length: 41.3 m 
  • Storage volume: 187 m¬≥ (gross); 173 m¬≥ (net) 
  • Corrosion protection: Z600 galvanization 
  • Minimum cover: 0.3 m soil 
  • Load rating: 60 t drivable surface at minimum cover 
  • Valves: 2 x Ø250 check valves (integrated in sumps) 
  • Access: Manhole brought to surface 
  • Connections: DIN-flanged nozzles for PE pipe tie-in 
  • Pressure testing: Factory tested by independent third party (Múlheim); site-tested per DBI 
  • Installation time: 5 hours