Implenia transport tunnel works in Stockholm 13 Apr 2017

Refurbishment of two rail tunnels in Stockholm is a key part of a contract package awarded by Trafikverket, the Swedish Transport Authority, to contractor Implenia.

Johannelund Tunnel on the E4 Stockholm highway bypass

Refurbishment is of the 600m long Soderstrom Tunnel and the 120m long Riddarholmen Tunnel, in the Getingmidjan area of the Swedish capital and on one of the country’s busiest sections of railway. The tunnel works are part of a larger railway upgrade package valued at SEK885 million (US$98 million) to get underway by mid-2017 and last about four years. Refurbishment of the tunnels is required as both have reached the end of their technical life, Implenia explained to TunnelTalk.

Soderstrom Tunnel was completed in 1950 and is a combination of three types of construction – concrete box, rock trench with a precast concrete roof and excavated rock tunnel. The improvement works on the tunnel are to be performed during an eight-week track closure in mid 2018.

The 11m wide Riddarholmen Tunnel was completed in 1955. Its structure is an untensioned, reinforced concrete frame with a watertight inner trough, explained Implenia. While shorter than the Soderstrom Tunnel, upgrade of the Riddarholmen Tunnel is being performed over 1.5 years as the tasks need close co-ordination with track replacement.

In the city centre location, and with a number of parallel works for Implenia and subcontractors in the narrow tunnels, the works are a complex logistical challenge. While complex, the tunnel works are only a small amount of the overall contract package, said Implenia.

Fig 1. Construction lots on the 21km E4 Stockholm bypass highway

The refurbishment works adds to underground works for Implenia in Stockholm, which include tunnelling on large parts of the E4 mega-bypass, most of which will be in tunnel.

In January, Implenia took on its latest contract package from Trafikverket on the E4 Forbifart bypass. The works, in contract joint venture with Norwegian contractor Veidekke, are at the Hjulstra Sodra section of the project and includes excavation of a 200m long tunnel.

Implenia is already working directly to the south on the E4 Forbifart bypass where it is constructing two major tunnels, the Lunda and Johannelund Tunnels, which are to be completed by April and December 2021, respectively.

The 1.6km long, twin-tube Lunda Tunnel, plus a 240m access tunnel, was awarded in mid-2016. The 3.6km twin-tube Johannelund contract, that includes link tunnels,ventilation shafts and 60m long cross passages, was secured by Implenia a year earlier.

Procurement of the Johannelund Tunnel was initially awarded to German contractor Bilfinger Berger, but Implenia acquired the contractor’s Swedish construction units when it sold off its construction division in 2015. The acquisition gave Implenia access to the German, Swedish and Norwegian markets.

Other recent contract awards on the E4 Forbifart bypass include major tunnels on lots FSE 302 (Norra Lovo) and FSE308 (Sodra Lovo), immediately south of Johannelund Tunnel and closer to the city centre. The lots were won by the Italian Vianini/CMC JV in August 2016 and account for two of the largest twin-tube tunnelling packages on the bypass at 3.5km and 2.8km, respectively. The contract confirmation followed some months an appeal lodged by rival bidder NCC but subsequently ruled against.

Procurement for the M&E packages is underway, including the tunnel ventilation lot (FSE903).