Preparations for the tunnelling works on the Victoria Station Upgrade (VSU) project for the London tube network to relieve peak time congestion are moving ahead – the public enquiry has entered its final stages and this month is the deadline for tenders to be submitted for the main works contract.

The public enquiry for the VSU project began on schedule in late October and is expected to last approximately two months. The shortlisted parties were invited in September to bid by December for the main works contract.

Subject to the outcome of the public enquiry, the client London Underground (LU) hopes to award the contract next year. The job will be awarded under the NEC form of contract, on a target cost basis.

The entire project, including preparatory works, is budgeted at just under US$1bn (in Q2-’07 currencies). The initial OJEU notice for the works, issued in January 2008, indicated a price range of US$685M-US$783M.

The project calls for the construction of a number of new passenger access tunnels, a new ticket hall and an enlarged ticket hall. Most of the tunnels will be approximately 6m high by 5.5m wide, and the largest bore on the project will be 9.3m high by 10m wide for the 30m long escalator barrel at the enlarged ticket hall.

The new passenger tunnels will be run over the main station tunnel due to restrictions in alignment in the local area. They will require both significant sprayed concrete lining (SCL) works, it is envisaged, as well as jet grouting. Most of the excavation will be above London Clay, in the waterbearing River Terrace Deposits.

The lead consultant for VSU is Mott MacDonald. LU and Motts have noted that such a construction method in the wet ground, and its scale, would be more like that undertaken in Continental Europe, such as at Cologne metro. However, the use of SGI rings has not been ruled out and would depend on contractor proposals (T&TI, June, p16-19).

Constructibility of the tunnel has been checked by the design team with support from London Bridge Associates and Gall Zeidler Consultants.

The ticket halls are to be constructed as open boxes. The new North Ticket Hall will be 75m by 30m and 10m deep, constructed in two phases. The enlarged section of the South Ticket Hall will be 30m by 40m and­ approximately 8m deep.