Bids from the shortlisted parties for the first of three large tunnelling lots on the West Link rail project in central Gothenburg, Sweden, are to be submitted by mid-May.

Artist’s impression of the Haga Station

Trafikverket, the Swedish national transport authority, told TunnelTalk that it has received “strong international interest” to prequalify for the three tunnel contracts, despite the hot construction market in West Sweden.

Five groups have been prequalified for the Haga lot in the middle of the 8km long project below the streets of the west coast city (Fig 1). The lot calls for excavation of the twin-track running tunnel, a parallel service tunnel, and an underground station.

Shortlisted groups, the names of which were not disclosed, have to submit bids to excavate the rock tunnels on a construction-only basis and to under take the station structure as a design-build element. Trafikverket expects to award the Haga contract towards the end of June, TunnelTalk was told.

Gothenburg West Link rail project contract lots

Visual concept of Korsvagen Station

After Haga, the next deadline is for four shortlisted groups to submit tenders for the Kvarnberget lot by 19 September. The lot is to the north of the Haga lot and although short, the tunnelling will be in complex soil-rock interfaces nearest the river and on a bend in the tunnel alignment.

The original schedule was for bids to be received at about the same time as for the Haga lot but this has been extended to September.

Five groups are shortlisted to bid for the last Korsvagen lot, which, as the longest section of the project, is located directly south of the Haga lot and comprises much of the southern half of the West Link. The bid deadline is 1 November and like the Haga lot, the rock and box elements of the package are to be procured differently within the single contract.

Trafikverket’s Project Director, Bo Larsson, told TunnelTalk he was “pleased with the pre-qualification phase” but noted the “challenge” of the building boom in western Sweden, which is expected to continue for up to 20 years. He had been looking for up to five shortlisted groups for each package.

Civil contracts on the two further Olskroken and Centralen lots, including a new station by the city’s main terminus, have been awarded to the Peab/WSP/Infranord JV and the NCC/Cowi/Thyrens JV respectively. The underground alignments in these sections, to the north end of the mostly underground West Link, are being built as cut-and-cover concrete box structures.

Swedish national transport authority Trafikverket is removing a serious bottleneck in the rail network through the urban heart of Gothenburg with investment in the 8km long West Link project. Three-quarters of the entire rail link and its three stations will be underground in both rock excavation and major concrete box construction. The line will increase rail capacity is vital for the west coast city of Denmark as it is a key industrial port and transport hub for Scandinavia.

Fig 1. West Link alignment and construction elements

The West Link project emerged from a transport strategy developed by Trafikverket in cooperation with the city and regional authorities, and is funded 50:50 from national and local funding. The estimated SEK 20 billion project (in 2009 prices), about US$2.5 billion, is anticipated to be in service by 2026.

The West Link has a 6km long section in single tube, twin-track tunnel and three new underground stations at Centralen, adjacent to Gothenburg Central terminus, Haga and Korsvagen (Fig 1).

Located beside the Gota River, the geology along the alignment has a variable rockhead, with small infilled channels and a major reach of infill and soft marine clay at the northern end (Fig 2). The bedrock is gneiss with joint sets, some foliation and zones of weakness in the rock mass. Groundwater levels adjacent to the river are high.

As a consequence, the majority of the tunnel, approximately 4km, will be excavated through rock. The remainder, in the northern part, will be built as a large concrete box structure through infill and clay over a 2km stretch (Fig 3).

The West Link is designed to take full size trains for its entire length. Dimensions of the tunnels are:

Rock Tunnels:

• Main tunnel - 14.7m wide by at least 10.1m high;
• Service tunnel running 10m parallel, to the main tunnel - 6m wide by at least 7.5m high;
• Technical rooms - 9m wide by at least 10.5m high

Concrete Box:

• Tunnel section - 15.6m wide x 9.5m high

The procurement and construction strategy splits the project into five main civil engineering packages: Olskroken, Centralen, Kvarnberget, Haga and Korsvagen. Trafikverket has awarded the Olskroken and Centralen Lots to date and prequalification for the next large tunnelling lots are due in by 30 September.

Fig 3. Proposed concrete box tunnel

Olskroken Lot

The Olskroken Lot, focusing on surface works at an existing central railway node, was awarded in 2015 to a JV of Peab, WSP and Infranord. It is a two-stage design-build partnering contract involving early contractor involvement (ECI). The contract sum is to be set at the end of Stage 1 design and planning, which is expected at the end of 2017. The construction Stage 2 will end in 2023-24 and may also include further ECI, subject to agreement.

Centralen Lot

The Centralen Lot for the station and adjacent tunnels was awarded to a JV of NCC, Cowi and Thyrens in 2015. Procurement is again a design-build/ECI two stage process with the contract sum to be set at the end of Stage 1 in December 2017 and with the Stage 2 construction anticipated in 2023-24.

The deep soft clay and bedrock of the Centralen Lot is seen as among the most demanding parts of the project. For the station alone, the works involve a cut-cover-cover excavation of about 400m long x 60m wide and to a depth of about 15m.

Proposed rock tunnels for the project

Various preparatory works are also underway including utility re-routing along the Olskroken-Residenset corridor. The SEK 150 million (US$17.5 million) contract is being performed by NCC and is due for completion in January 2017.

Ongoing procurement activities are most immediately focused on the upcoming prequalification deadline of 30 September for the Haga and Kvarnberget civil lots located in the middle of the project. Tender documents are to be issued to prequalified parties in November for submission of proposals by April 2017.

Trafikverket Project Director Bo Larsson told TunnelTalk there will be a maximum of five prequalified parties for the main contracts. Larsson confirmed that the excavation method for much of the rock tunnel is expected to be drill+blast and added that optimisation of the tunnel design is still underway.

Impression of Korsvagen station on the West Link rail project
All photos by Trafikverket

Haga Lot

Key civil works involved in the Haga package involve construction of 1,520m of main tunnel with 1,220m in rock and a 300m long section of concrete box tunnel for the station, plus 1,310m of the parallel service tunnel in rock, and construction of three entrances and three ventilation shafts.

Total excavated volumes of rock and soil at the Haga Lot are expected to be about 650,000m³ and 340,000m³, respectively.

Within the one contract lot, Trafikverket has separated the rock excavation as construction-only and the concrete box works as design-build.

Kvarnberget Lot

Works for the relatively short Kvarnberget Lot, on a bend of the tunnel alignment and running closest to the river, features complex works through rock-soil interfaces.

Site investigations underway

Korsvagen Lot

Deadline for prequalification to the last main civil lot on the project, the Korsvagen Lot at the southern end of the project, is 15 December. Tender documents are to be issued to prequalified parties in February 2017 for submission of proposals by October 2017.

The Korsvagen contract package includes a total length of 3,240m in main tunnel, split 2,120m in rock and 1,020m in a concrete box structure for the station, plus a 2,540m long section of the parallel service tunnel in rock and three entrances and two ventilation shafts.

The total volumes of excavated materials in the Korsvagen Lot are 761,000m³ of rock and almost 400,000m³ of soil.

Like the Haga Lot, Trafikverket has separated the procurement method of the Korsvagen Lot to construction-only for the rock excavation and design-build for the concrete box works.