Vantaa light rail tunnel advances beneath Tikkurila

Construction of Vantaa’s most expensive and challenging light rail project is advancing in Tikkurila, where an 820-metre tunnel is being built beneath the main railway line, Yle reports.

The tunnel will run from Väritehtaankatu to the area of the Tokmanni store. A light rail stop will be built beneath Tikkurila railway station, allowing passengers to transfer directly to trains underground.

“This is certainly the most expensive individual part of the project because we are going so deep underground,” said Juha Viitala, production manager for the light rail project’s western alliance.

The excavation will reach a depth of 15 metres at its deepest point. The tunnel is being built using an open-cut method, in which a large trench is excavated before the tunnel itself is constructed.

Groundwater poses the biggest challenge

Tikkurila’s ground is mainly soft clay, requiring very substantial support structures for the excavation. The biggest challenge is groundwater. Its level varies by about five metres, meaning the tunnel is being dug approximately 10 metres below the groundwater level.

“The groundwater is under pressure. We have to make sure that too much water does not leak into the excavation,” Viitala said.

Groundwater levels are monitored daily. Water entering the excavation is pumped back into the groundwater, and the completed tunnel will be made watertight.

Because the tunnel is deep and must be completed within three years, construction is taking place at several points simultaneously. Four separate logistics ramps lead to the site.

Construction underway along much of the route

Work is progressing across much of the light rail route, although some streets have not yet been opened for construction. In the Porttipuisto area along Kyytie, workers are building stormwater pipelines and support walls. The pipelines will carry rainwater away from the streets.

The large construction project has drawn both opposition and support from Vantaa residents. Project director Hannu Lehtikankare said he understood that the site was disrupting daily life through temporary traffic arrangements and diversions.

Residents living near the construction site also hear drilling and blasting and are affected by dust. Lehtikankare said the site would be an unpleasant neighbour during the construction years, but that the final result would be rewarding.

Vantaa’s light rail line is planned to be completed by the end of 2029. The route will run from the airport to Mellunmäki in Helsinki, and its updated total cost is approximately 750 million euros.