Renovation of Päijänne Tunnel in full swing
The renovation of the southern part of the Päijänne Tunnel is progressing according to plan.
The air in the Päijänne Tunnel has the distinct odour of a damp cellar. There is some ground water seeping through the ceiling and wet fine clay squelches under the rubber boots.
“Soon one will be able to drive a car through here directly under the Silvola reservoir”, says director of construction site supervision Jari Heikkilä of Ramboll Finland engineering services.
We are standing at an intersection of a bit of tunnel leading north and south about 25 metres underground.
In the pitch-black tunnel, 64 men work in three shifts round the clock.
The emptying of the tunnel, begun in mid-April, has advanced to the stage where a third of the first section of the tunnel’s southern part has now been cleared of water by pumping the water onto the surface.
Because of the renovation of the tunnel’s southern section, the tunnel has to be emptied of water from Pitkäkoski all the way to the Kalliomäki power plant in Hausjärvi.
The need for some maintenance work emerged five years ago, when a diving robot observed the initial stages of cave-ins in the walls of the tunnel.
“Ninety per cent of the tunnel is in excellent condition, but the sections that are in only moderate shape will be reinforced to add to the reliability of the watercourse”, Heikkilä explains.
In the southern section of the tunnel there are 11 separate water reservoirs, from which the water originating from Lake Päijänne is pumped onto the surface by using 11 pump chains, each of which consist of three separate pumps.
The actual renovation of the tunnel walls advances in three stages. First, any loose stone matter is knocked off the ceiling and the walls. After that rock bolts are fitted into the tunnel, and to fortify the enforcement concrete plastering will be blasted onto the rock surface to cover around 14 hectares of the tunnel walls.
The Päijänne Tunnel is the pride and joy of the water men. “I doubt that today we’d have enough consensus to take on such a project any more”, says Helsinki Water operating manager Veli-Pekka Vuorilehto referring, for example, to the concert - or more precisely the lack of it - that exists between communities and land-owners.
Vuorilehto commends the planning of the tunnel given the available knowledge and construction methods at the time when the work was carried out.
Especially the turbine that regulates the flow of water from Lake Päijänne to the Silvola Reservoir receives praise from Vuorilehto. “The water turbine also produces electricity to the national grid, which reduces the use of resources in purifying the water. The tunnel is a prime example of a sustainable development investment.”
Previously in HS International Edition:
Residents of Central and East Helsinki will be drinking River Vantaa water by the weekend (15.4.2008)
Helsinki drinking water to be drawn from River Vantaa from mid-April (31.3.2008)
Study finds tap water purer than bottled water (15.2.2008)
Helsinki.fi: The renovation of the Päijänne tunnel starts 15th April
Päijänne Water Tunnel (Wikipedia)