According to the official statement that has been distributed on 6 October 2010, the probable origin of the glycol is aircraft de-icing fluid. Mixed with oxygen glycol breakdown products facilitate microbial growth in the water seeping into the tunnel and on walls. The resulting microbe population contains high bacteria concentrations. “At this stage it is difficult to say how hazardous the microbe population in the tunnel is. Most likely bacteria normally found in soil have started to grow in seepage water and on walls because of glycol, which the bacteria are able to use in metabolism.

The National Institute for Health and Welfare has taken samples for testing and the results will be ready soon”, says the statement of The Finnish Transport Agency.

Work in the tunnel has stopped until environmental and health authorities will study the matter.

The microbe population has been observed only in this part of the tunnel and not along the rest of the Ring Rail Line.

Possible impacts

The microbe population may cause major delays in the Ring Rail Line project, since construction work in other contracts will possibly have to be postponed as well. Construction of the Airport station will definitely be postponed if the microbe population causes delays in excavation work or a way to keep it out of the tunnel cannot be found quickly. Contaminated water must be kept out of the tunnel because it contains acids that have a corrosive effect on concrete. The water must be drained off into reservoirs.

The cost of necessary measures cannot be estimated for sure at the moment, but they could reach as high as several million euros. Total costs will depend on what solution is used to keep contaminated water out of the tunnel.

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