The JV of Salini Tecnimont and Seli is heavily into planning for the large scale TBM tunnelling works and deep box station excavations needed for Cityringen, the latest addition to Copenhagen’s metro network. Known as Copenhagen Metro Team (CMT), the JV was formally awarded the contract to build the 15.5km long loop of twin tubes through the heart of the Danish capital, along with 17 new stations.
The client, Metroselskabet, recommended the award in late November 2010, pending approval by its owner, and the EUR 1.7bn (USD 2.38bn) contract was confirmed in January. At the same time, Ansaldo was awarded the separate contract by the client for the control systems and driverless trains, which are to commence services in 2018.
Procurement was a long process for this major project, starting in 2009. In early planning the loop was split into two tunnel packages (North, South) for the bid process, and it was not determined until later whether to also allow offers to undertake the entire works. Closer to the bid phase the option was taken, which created a wider mix of possibilities to weigh from the range of JVs on the tender shortlist – three groups, eventually, one having dropped out.
While a single infrastructure contract to build the whole metro line was eventually chosen by the client, offering at least economies of scale, Metroselskabet noted when the contract award was recommended, late last year, that the build cost for the entire scheme was still higher than it had initially expected. However, it added that negotiations have chopped the extent of the increased cost and also that the low interest rate environment has helped to offset the impact and so keep the overall cost within budget limits.
Extra money did not have to be found for the underground transport project, which is budgeted, in entirety, at DKR 21.3bn (USD 4bn).
As planning and programming are being advanced and refined, the construction schedule currently envisages that tunnel boring will start around the middle of 2012. Seli will perform the TBM drives, and the other members of the JV will undertake construction of the deep box stations.
A JV of Cowi, Arup and Systra worked with Metroselskabet in the project development phase to prepare the civil design to the tender stage. The client is now working with the consultants’ consortium to develop the construction management (CM) organisation for the build phase of the project. The CM organisation will include a management team and part of the supervision team from Metroselskabet supported by staff seconded from the consortium.
Project preparations
Copenhagen’s metro operates two driverless train services, M1 and M2, on a Y-shaped network. The lines are a combination of surface and tunnel sections, the underground parts running at the centre of the ‘Y’ and running through the middle of the city.
By building the entirely underground Cityringen loop on top of the ‘Y’, Metroselskabet will add significant capacity to the expanding metro network, for which Copenhagen Municipality provided funding for branch lines and construction of stub tunnels as part of the forthcoming tunnelling works.
The M3 and M4 train services are introduced with driverless trains running every 200 seconds and 100 seconds respectively. It will take about 24 minutes to travel the circle line on an M3 train, and the services on Cityringen are to operate around-the-clock.
Studies for Cityringen began in 2003, funding was agreed in late 2005, legislation passed in June 2007 – although further approval would be needed – and initial design work started in 2008. The preparations overlapped with the development of the ‘Y’-shaped initial network, built over 2002-7 in three phases.
Site investigation along the alignment was extensive where the tunneling conditions are relatively favourable, and there is previous experience with large TBM drives for the early metro construction. Archaeological investigations were also undertaken along the route.
Geology is glacial moraine over limestone (half the alignment) with groundwater pretty close to the surface. In the northwest quadrant, near Norrebro, there were extra surveys performed at the thicker sand beds – meltwater deposit – between layers of Clay Till – moraine – in the area. In Norrebro the limestone is at a depth of 30m-35m.
The internal tunnel diameter was not specified from the outset to be the same as the existing metro – 4.9m i.d. – but in the end this is also to be the size of the Cityringen tubes. The shields are to bore at depths of 15m to more than 30m, possibly 35m according to the pre-contract award outline design but the vertical alignment will be settled with the contractor.
The box stations will have standard lengths of 62m and be excavated to varying depths, averaging 18-19m, though some being up to about 28.5m, and with platform 13m below ground surface.
Tunnelling work also calls for construction of four crossovers, the stub tunnels, and also five shafts – 15 fewer than in initial plans.
Procurement
Metroselskabet began preparations to start procurement of the main construction contracts in 2009. The preliminary steps involved the prequalification process and drawing up a shortlist of JVs approved to bid. Tender documents were issued in late 2009.
Early planning had envisaged contract award by mid-2010 but bids were only submitted in May. The line remains on schedule to be opened in 2018.
A two-stage bid evaluation process was followed, with the initial price coming in a bid-opening ceremony, followed by a period of technical evaluation and then negotiations, until September.
Rival bidders for the tunnel works were the following JVs: MT Hogaard with Hochtief, Ed Zublin and E Pihl & Son, and Alpine Bau with FCC Construccion. Early in the procurement process the prequalified JV of Bilfinger Berger, Per Aarsleff and Vinci pulled out.
Salini said in mid-2010, after bid opening, that it had made the lowest offer for the two lots combined, followed by those offers from JVs led by MT Hogaard and Alpine, respectively. It added that the JV was in second place for one of the individual packages – the South contract. Contract award had been expected to be made about September last year but the bid evaluation process took another couple of months, to November.
Salini commented on the client having visited its tunnelling works on the Line B1 metro project in Rome, which is ahead of schedule, it reports, and also noted the recent B2 award. Seli is also working on the project. They said that the Danish client was able to see their approach to minimising impact on the city’s inhabitants, and using local workforce and companies where possible.
Following the extensive procurement period and negotiations, Metroselskabet noted that the building costs for Cityringen came in approximately DKR 3bn (USD 560M) higher than expected in its early planning work.
Henning Christophersen, chairman of the board of Metroselskabet, said late last year at the results announcement of bid competition: ‘The price of the construction has risen, but we are satisfied that we can finance the budget ourselves through savings on interest expenses, which means that our owners will not have to find new funding for the project. The overall financial situation is thus unchanged.’
But, as Metroselskabet further noted, the negotiations had managed to reduce the costs from even higher levels over the early budget estimate. It managed to cut the price by around DKR 4bn (USD 750M)
Henrik Plougmann Olsen, chief executive, said they succeeded in reducing the price while dealing with the tenderers’ reservations.
The proposed award of the tunneling and underground construction contract to the Salini-led JV was announced on 24 November 2010, and then, following approval by Metroselskabet’s owners, it was signed on 7 January 2011.
Construction phase
Cityringen is an extremely complex project since the Danish capital is at sea level, groundwater levels are high and large numbers and volumes of excavations are required. And, not least, environmental regulations for groundwater protection are extremely important.
The JV has four EPBMs are to be used to bore the twin tubes for Cityringen, which is about the same number as the estimate (4-5) given by the client in early planning work prior to commencement of the procurement phase. Metroselskabet expected there would either be EPBM or slurry shields, or a combination, used on the project.
The first of the 5.78m diameter shields is to be launched around the end of the third quarter, or early in the fourth quarter of 2012, around 20 months or so after contract signing.
Aside from the work sites at the stations, the main construction sites for the project are at Norrebro Park, Oster Sogade (near Trianglen station), and the Control and Maintenance Centre, Tommergraven area, in the north and south of the project.
An additional construction site, notes Metroselskabet, is for cover and cover construction at Sonder Boulevard. It is needed because the intended sprayed concrete bifurcations will not be used to form the tunnel junctions due to difficulty of employing the method in a hazardous working environment that will result from dealing with a known ground contamination having been found to extend into the main aquifer in the area.
With the Salini-led JV responsible for detailed design under the contract, the coming months will see the focus on establishing and refining plans for the optimum solutions in construction and cost across the job. Time will be needed to settle the designs as well as have the details and proposals approved by the client.
As such, the finishing locations of the TBMs, for example, are to be determined later, and the split of the drives between the machines to cover the 31km total length of the parallel tubes has also to be decided.
So, too, is the question of concrete segment production. While the design parameters of the segments is known – 300mm thick to form 1.4m long rings (5+1) – it has yet to be finalised which companies will supply the moulds and manufacture the segments. Comparatively, the existing metro tunnels have 275mm thick segments, and also six-part rings.
What is determined, though, is that Seli will perform the tunnelling activities for the JV and also supply the main boring and back-up equipment. Seli has noted that the EPBMs and auxiliary equipment is valued at approximately EUR 40M (USD 56M). The company added further that with the award its acquired backlog of projects has risen to EUR 800M (USD 1.12bn).
One change in station design, notes Metroselskabet, will also mean that the tough construction work to carve out a station cavern at the base of a slimmer-than-standard box structure for Marmorkirken station is no longer to be done. The station, named after the adjacent old church of the same popularised name, meaning ‘The Marble Church’, has had its layout and construction method changed to stack the tracks within a slightly deeper box structure instead of trying to keep them at the same elevation. The station name has also changed, from Frederiks Kirke, the official name of the church.
Tunnel excavation is to be completed by around mid-2016, which will then see 2013-15 as the peak period of TBM excavation below Copenhagen.
Map of Copenhagen’s existing metro lines and next to be built – the 15.5km long Cityringen ‘loop’ Cityringen will have 17 box stations excavated underground Cityringen tunnelling and station works are being done under a single contract Early preparations underway for the construction site at Norrebro, in the northwest of the city
