Maunsell Consultants Asia
Contract DD-210, 5.1km including two stations
Design contract value HK$172M (£13.8M)
Both Tuen Mun North and Tuen Mun Centre stations are over a major drainage channel, or nullah. The challenge is to avoid building a structure that would interfere with this, says KCRC northern section project manager Gregory Yuen.
A further constraint is that no work will be possible over the nullah in the rainy season, so piling will have to be spread over two seasons.
The line is above ground in this area, and both stations lie right over the nullah.
'We have to be sure that the capacity of the nullah isn't unduly affected and that maintenance can be carried out,' Maunsell director George Gillott says.
Flooding levels and margins are given, and these cannot be exceeded, nor can turbulent flow be created.
The nullah is tidal around Tuen Mun Centre, and the contractors will have an additional challenge in dealing with the sea, Gillott says.
'It places a severe limitation on the construction,' Gillott observes.
About 3.5km of the track in this section is elevated. Arup has taken the lead on the viaduct design, and Maunsell has adopted this in its section; the station designs are also co-ordinated.
Ancillary works include relocating a school, replacing a park and various road upgrades.
Tuen Mun Centre station is being built over both an LRT bridge and a road bridge - a major engineering exercise, says Maunsell managing director Tony Shum.
A structure spanning 32m, founded completely within the nullah, and built high enough to avoid obstructing the flood path, will hold up the station. The structure is founded in rock 20-30m below.
'Where we are spanning over the bridge, the structure is steel for ease of erection and because the loads demand it. The rest is conventional reinforced concrete,' Shum says.
Tuen Mun North station is in three parts, with the rail station at the centre and passenger transport interchanges - including a major one with the light railway - at either end.
Upgrading of the LRT, recently announced, will be taking place at the same time, and the design has to be updated to take account of this. Architect is RMJM.
The design timescale has been very short. 'We were appointed in March and produced draft tender documents in October for £400M of work,' says Gillott.
'Even for Hong Kong that's impressive,' adds KCRC's construction engineering manager Chris Calton.
'We have also spent a lot of effort in reducing the amount of concrete and steel,' says Shum. Value engineering studies (see page VII) have led to both stations being considerably compacted.