Start of excavation work for the ventilation and hoist building
Excavation work for the ventilation and hoist building has begun at the ONKALO construction site at the end of November and will continue until January. Contractor for the excavation work is Lännen Kaivuu ja Louhinta OY. The ventilation and hoist building will be completed during 2011, after which the ventilation of ONKALO will be handled through it.
For the time being, the ventilation of ONKALO is being taken care of by having the inlet air into the tunnel through the exhaust air shaft and exit the tunnel through the personnel shaft. The exhaust shaft also serves as the emergency exit, with a rescue basket for transporting up to five people installed into the shaft. In the future, the plan is to move the rescue basket into the inlet air shaft and thus it will be operated from the hoist building.
As the name suggests, the ventilation and hoist building is comprised of two buildings. The hoist building will be built on the location of the inlet air shaft, and the ventilation building near the shafts. A tunnel will be built between the hoist and ventilation buildings, through which the air into the inlet air shaft will be directed. Respectively, a channel will be built between the exhaust air shaft and the ventilation building for the expulsion of air.
The ventilation of ONKALO will be transferred to take place through the ventilation building in 2011. At that point, the shafts will have reached their greatest depth at -437 metres by the raise boring method used. At present, the shafts have reached a depth of -290 metres.