The HK$7 billion Hong Kong Boundary Facilities (HKBCF) reclamation, a key element of the Hong Kong Zhuhai Macau bridge (HZMB) infrastructure, has encountered a serious problem – it is moving, or at least parts of it are.
Civil engineers familiar with the artificial island which is being built next to Hong Kong International Airport, say that part of the reclamation once moved 20 metres and there have been other movements in different parts of the island of up to 7 metres. The project is so sensitive that construction professionals involved with it say they have been forbidden to discuss it.
The Highways Department has admitted in an email to HowardWinnReports.com that movements “of up to 6 or 7 metres” have occurred in various parts of the reclamation. This, the department says, is the result of adopting a non-dredging seawall construction method which is being used in Hong Kong for the first time.
The Highways Department said in its email that the reclamation was unlikely to be completed by the end of 2016, which is already a year later than its original completion date. It is also a departure from a government press statement in November 2014 in response to media comment about possible delays, that the HKBCF would be completed by the end of 2016. HowardWinnReports.com has been told by engineers that much of the work at the site has halted and a review is underway to consider how to deal with the problem.
The HKBCF reclamation is being constructed by China Harbour Engineering Company at the Northeastern tip of the airport, opposite the Hong Kong SkyCity Marriott Hotel. It is a 150-hectare artificial island of which 130 hectares will be used for passenger and cargo clearing for traffic using the Hong Kong-Zuhai-Macao bridge, while the remaining 20 hectares will provide the landing point for the tunnel linking the artificial island to Tuen Mun. The HKBCF according to the HZMB website comprises cargo and passenger clearing and vehicle inspection facilities, offices for the Immigration Department and Customs & Excise, along with road networks, and a public transport interchange.
The HKBCF is a key hub without which traffic cannot flow across the new bridge. It is understood that attempts to prepare the foundation work for buildings to be erected on the site have had to be abandoned. When piles were driven into the bedrock on the site of the passenger clearance building, the piles were subsequently found to have moved by 100 millimetres which means they had broken or had bent, according to engineers.
When the reclamation contract was awarded back in December 2011, much was made of the environmentally friendly non-dredging sea wall construction that was to be employed in Hong Kong for the first time. The site of the reclamation comprises a considerable amount of soft mud. The conventional approach would have involved dredging this soft mud down to bedrock and filling it with marine sand, an approach which causes considerable ecological damage by disturbing the seabed, the quality of the water, and additional noise which is particularly disturbing to the pink dolphins in the area. Also there is no need to transport and dump the dredged marine mud causing ecological problems elsewhere or to find and transport tons of marine sand.
The non-dredge approach involved building a sea wall comprising big steel circular caissons with a diameter of about 30 metres. These were dropped into the sea three to four metres apart and joined by a flexible steel wall. Each caisson weighs about 450 tons empty and as the mud is dug out from the middle it drives itself down until it reaches a hard strata.
Many of the reports on this project refer to the “tight construction period,’ since it is supposed to ‘dovetail’ with the commissioning of the HZMB. To speed up the settlement process a surcharge of additional weight is applied to the caissons and the soft material in the sea bed is squeezed out from under them. When the surcharge is withdrawn the hope is that the caissons have reached final settlement. Inevitably, engineers say, one part of the caisson hits hard strata first. Sometime there can be large difference in settlement at different parts of the caisson. In its email to HowardWinnReports.com, the Highways Department says the soft mud can vary in thickness from 10-30 metres. Because of the huge weights and pressures involved, the caissons can distort and sometimes tip and move. An engineer familiar with the project says that many of the caissons are still settling or sinking at a rate of 100 millimetres per month. The sea wall is not expected to fail but it may not keep the correct shape.
“The problem is that once again Hong Kong has allowed itself to be bullied into building this too quickly”, said one experienced engineering consultant. In the past Hong Kong has left reclaimed land to settle for between 5-15 years before building on it. “The problem with the HKBCF is that it hasn’t been left long enough and it is still settling.” Engineers are still considering what to do about the problem.
Meanwhile the clock is ticking for other projects that need to be built on top of the artificial island and to link to it. Contractors involved in erecting infrastructure on the building on the island are being kept waiting. Meanwhile Dragages Hong Kong is boring two 4.2 kilometre long two-lane road tunnels under the sea between Tuen Mun and the artificial island. At a contract price of HK$18.2 billion it is the biggest contract ever awarded in Hong Kong. It can’t complete the tunnelling until the reclamation is stable. If, as is possible, Dragages and the other contractors involved with HKBCF related project, are delayed then there are likely to be significant demands for compensation, further increasing the overall cost of the project.
In its email the Highways Department, no doubt with an eye on future criticisms and recriminations for adopting this non-dredge approach, is downplaying the project’s technical problems.
“This kind of movement is normally found among large-scale reclamation projects adopting a non-dredge method in the main reclamation, with the HKBCF artificial island no exception,” the department said.
However in explaining why the project will be delayed it says, “having regard to challenges such as unstable supply of materials, shortage of labour, restriction in airport height and constraints in environmental protection requirement, the HKBCF project may not be completed in time by end 2016.”
A consulting engineer said that while it was true that these were valid factors, “blaming the problems on these factors covers up the technical failures and gives them a nice excuse to justify delays which have been generated as a result of having to fix the engineering issues before being able to progress.”