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  Isolation structure in Ring Rail Line

  The Ring Rail Line is an important circular route of the Helsinki Metropolitan Area. It is an ur ban rail line and a rail connection to the Helsinki-Vantaa airport. During excavation works under the Helsinki Vantaa airport liquid fluid was noticed leaking into the tunnel, which by odour is related to anaerobic process es. The fluids contain nutrients that enable the growth of microbes. The investigations showed that ground water at a minimum pH under 5 is acidic and contains antifreeze agents as ethylene and propylene glycols which have been used decades in aviation. In aerobic conditions the glycol based fluid forms alcohols and organic acids, most relevant of them acetic acid and propionic acid. The growth exhibits a distinctive odour, which is undesirable in public venues. The growth can also block drainage pipes. The growth has some effect on con crete structures but a larger influence on steel structures. After investigations it was decided that an isolation structure was to be constructed for the railway tunnels and part of the railway station.

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