Merko-led consortium completes Ülemiste junction ahead of deadline

Tomorrow, one of Estonia’s most complex integrated infrastructure projects, the Ülemiste traffic junction, will be opened for traffic. A consortium led by Merko delivered the project ahead of the deadline. The junction consists of a 680-metre-long tunnel for automotive traffic, three tunnels for cyclist and pedestrian use, and a 150-metre overpass. The large-scale construction project was made more complicated by the high water table in the vicinity of Lake Ülemiste and the fact that work took place in an area with heavy traffic flow, an operating train service and live utility lines. The junction has 8.7 km of carriageway and 7 km of non-motorised cycle and pedestrian track, with a total of 155,000 square metres paved with asphalt. At its deepest point, the construction work took place 16 metres below the surface of Lake Ülemiste.

The construction of the Ülemiste junction was carried out by the consortium consisting of AS Merko Ehitus Eesti, AS Merko Infra, Tallinna Teede AS and AS Ehitusfirma Rand & Tuulberg. Project manager for lead partner Merko Ehitus Eesti, Tiit Joosti, said the Ülemiste junction was a fully integrated site that was built in the midst of existing functioning infrastructure. He emphasized that the visible parts of the new junction are only the tip of the proverbial iceberg; most of the complicated work lies out of sight, below the surface.

As part of the procurement for the preliminary work for the junction back in 2010-2011, Merko Ehitus Estonia established a storm drain system with a total length of 2.5 kilometres, situated up to 16 metres below ground. These lines route runoff from Järvevana road, Tehnika street and Filtri road from underneath Zelluloosi street via Lasnamäe street into open concrete channels running through Kadriorg Park. In addition, in the same period and likewise as part of the procurement, Merko Infra established a transition between 110 kV overhead electrical lines to buried cable. This was required for building the Tartu highway overpass and the cycle and pedestrian paths.

From a construction aspect, the most complicated part of the junction was the 680-metre tunnel segment of the project, of which the actual underground tunnel section makes up 320 metres. The tunnel construction required constant work in a high water-table zone and the deepest part was 16 metres below the surface of Lake Ülemiste. The second important part of the junction is the 150-metre overpass that routes the flow of traffic from Peterburi road over Tartu highway to Järvevana road. Each direction of traffic uses a separate span structure. The bridge was erected on variable height reinforced concrete beams with a rectangular cross-section, with post-tension reinforcement.

The tunnels for the carriageways in either direction are 8 metres wide and 4.6 metres high and connect Järvevana road with Peterburi road, passing underneath the railway. Each direction has its own structure – two reinforced concrete structures have been built for the tunnels, connected to each other by emergency exit routes. The tunnel is anchored to the ground; the ramps have anchors for the upward force exerted by water.

Merko Ehitus Eesti’s project manager Tiit Joosti said regarding the tunnel construction’s technological design: “First we built an underlying drainage layer, then technical concrete, on top of which we established hydro insulation and concrete structures. The tunnel itself is completely covered by hydro insulation underneath, on top and on the sides, and the sides have drainage mats so that the tunnel would not disrupt normal water circulation in the area – water moves to the tunnel, passes through the mat, goes underneath the tunnel and, based on the principle of communicating vessels, rises up on the other side.” To lower the water table during tunnel construction, an up to 17 metre long trench surrounded by sealed wall elements was established and submersible pumps and needle filters were used to remove the water, which constantly sucked up the water from the sand.

The influx of water from below and above continues in the case of the finished tunnel; and in order to collect rain and snowmelt into storm drains, the pavement is built at a lateral and longitudinal angle toward drains connected to storm sewers. From there, the water flows downhill to the sea via underground storm sewers and the open concrete canals through Kadriorg Park.

To ensure safety, the situation in the tunnel is monitored by an electronic safety system, which detects any hazardous problem – fire, accident or other problem and regulates the situation using traffic signs with an electronic readout. The human supervisor then checks the real situation on the video recording and decides whether to close the tunnel. The tunnel has emergency exits – at intervals of less than 90 metres and equipped with fire doors – for the purpose of ensuring human safety. In addition, the tunnel also has a smoke exhaust system. The tunnels have smoke removal fans, which are switched on rescue personnel manager arriving at the scene in case of accident. There are also evacuation routes for people, which have illuminated markings and lead people out of one structure to the other and then out of the tunnel.

The safety of pedestrians and other non-motorised road users is ensured by the Ülemiste junction bicycle/footpaths and tunnels, which connect to the rest of the Tallinn bicycle path system. They can be used to get between Järvevana road – Veerenni street and Järvevana road – Filtri road and Tehnika street without crossing a road used by motorised traffic. The Järvevana bicycle/footpath connects Järve recreational path and the Haabersti bicycle path network with the Tartu highway area. The Tehnika street bicycle/footpaths provide a connection to the city centre from Veerenni street and the bus station.

 Facts about Ülemiste junction:

• 7.5 km of new roads and paths, and 1.2 km of rebuilt roads and paths, total area of asphalt pavement laid – 155,000 m²
• Two tunnels for motorised traffic, 150-metre-long overpass
• Three tunnels for bicycle and foot traffic, built using a technical design similar to the one for the carriageways
• 5.35 km of new non-motorised routes for bicycles and pedestrians, 1.65 km rebuilt, width ranging from 2m to 4.5 m
• The dedicated site crew was 20 strong. There were also many pipe layers, utility line and concrete pouring crews, with 250 workers on site on peak days.
• 12 hectares of green space established as part of the project, with hundreds of trees and thousands of shrubs planted
• As part of the procurement for the groundwork for the junction project, the following was built:
  • a storm drain system and close to 2.5 km of underground water drainage canals and mains ranging up to 16 metres below ground in places, leading from Ülemiste to Kadriorg
  • a 110 kV overhead line was connected to buried line, which was required for building the Tartu highway overpass and cycle and pedestrian paths

The Ülemiste traffic junction is one of the most important crossroads in Tallinn, where Tartu highway, Peterburi road, Suur-Sõjamäe street, Järvevana road and the railway all intersect.

The construction contract was signed in late 2010 between Tallinn Municipal Engineering Services Department and the consortium of joint bidders consisting of AS Merko Ehitus Eesti, AS Merko Infra, Tallinna Teede AS and AS Ehitusfirma Rand & Tuulberg.