Cutting through densely populated Po Lam and Hang Hau has presented a major community relations challenge to contractors and client alike. 'The line runs through the middle of an area of occupied housing, ' says Section 2 project manager Roger Bettiss.
The entire section runs through reclaimed land and the risk of settlement requires extensive and noisy piling down to bedrock to stabilse track and stations. Station and tunnel contracts also include extensive piling in advance of associated high rise property developments, profits from which will help fund the new line.
The close proximity of high rise flats places limits on contractors. Working hours are restricted to 7am and 7pm, six days a week, shutting down on Sundays and public holidays.
Contractor Maeda Corporation is now well into construction of the Po Lam terminus with platform construction in full swing. Po Lam Station stands at grade at the shallow end of the reclaimed site through which the four Section 2 contracts run.
Heading south towards Hang Hau station, the bedrock level falls away steeply, and extensive piling and excavation work are needed to take track and station foundations down to bedrock.
This makes Dragages et Travaux Publics' HK$1.28bn contract a sensitive one for local residents. In all the contractor has to insert 122 bored piles to depths of around 30m for the station.
And 133 more bored piles are going in for six neighbouring high rise property developments overlooking the site.
At Hang Hau station, trenches for diaphragm walls also have to go down to bedrock, all on a tight 40m wide site.
Residents will be relieved to know that most of the foundation work for this section of the station is complete. Excavation of the station box is unlikely to be as noisy, as the contractor has opted for top down construction.
Dragages' Hang Hau contract has the worst combination of intensive piling, excavation and densely packed housing. Despite this the contractor has risen to the challenge. 'Dragages has acted very responsibly, ' says Bettiss. 'It has had to deal with a lot of issues it shouldn't really have had to.' The contractor has helped MTRC by talking to local residents, addressing their concerns about noise, dust and subsidence.
MTRC has also organised regular school visits and meetings with residents to explain how the apparent chaos on site will produce a live railway by 2002. 'We are trying to build up relationships with the community. At the end of the day they want the railway, but they are being extremely tolerant, especially during the sheet piling, ' says Bettiss.
The southern limit of the Dragages contract takes in a bifurcation tunnel where the line will split, with a branch off to the depot. Here the line has to pass under a series of roads and a huge box culvert stormwater sewer.
Before the tunnel can be excavated, the contractor has to insert a series of 600mm diameter secant piles under the outer edges of the four cell culvert structure. Just before Christmas, Dragages had begun to remove the backfill around the box before inserting the piles. When in place these piles will form the temporary support wall for the construction of the running tunnel.
Construction of the cut and cover Tseung Kwan O station and tunnels has been much more straightforward, because the closest housing estates are still under contruction. But sharing access roads with these developments and with Tiu Keng Leng station brings a new problem of traffic congestion.
Tiu Keng Leng station stands in a deep rock cutting at the portal of the Black Hills tunnels. Here, four lines emerge in pairs, on two levels, feeding into the station which will act as a double deck interchange between the extended Kwun Tong line and the Tseung Kwan O extension. The station site was formed by Gammon in a massive advance excavation contract, which involved blasting and removing 1.3M. m 3of rock from the Black Hills for the station and tunnel portal, plus levelled pads for 23 blocks of flats for government and private development.