Western Harbour Tunnel - Hong Kong's quickest cross-harbour traffic route

WHC Project

In 1989 the Government decided to develop a new international airport for Hong Kong on a site formed from Chek Lap Kok, an island just 3 km off Lantau Island. This was to replace Kai Tak International Airport, which would reach maximum capacity in the mid 1990s.

Nine further infrastructure projects - collectively known as the Airport Core Programme (ACP) - were associated with the development of the new airport. These were Tung Chung New Town, the North Lantau Expressway, the Airport Railway, the Lantau Link, the Cheung Tsing Tunnel on Route 3, the West Kowloon Reclamation, the West Kowloon Expressway, the Central and Wanchai Reclamation, and the Western Harbour Crossing.

Unlike all the other ACP projects, the Western Harbour Crossing (WHC), now more often called the Western Harbour Tunnel (WHT), is a franchised infrastructure, completely financed by the private sector at a cost of HK$7 billion. It remains Hong Kong's single largest private sector transportation project.

Location Linkage

The Hong Kong portal of WHT forms the southern gateway of Route 3, the strategic north-south road corridor that traverses the western part of Hong Kong. The tunnel thus links major population centres in Hong Kong, the container port in Kwai Chung and the Hong Kong International Airport, etc. It also opens up the northwestern New Territories and connects with many superhighways to Guangdong via Lok Ma Chau.

WHT not only releases the traffic stress at the other two cross-harbour tunnels, it also shortens your travelling time between Hong Kong Island and Kowloon.

Project Scope

The construction of WHT was split into several sections:

1. Elevated Bridges in Sai Ying Pun on Hong Kong Island

The existing elevated section of the east-west distributor road on the north of Hong Kong Island was extended towards west to form the first section of Route 4, the planned coastal road to Aberdeen. The elevated length of Route 4 contained 17 separate bridges and ramps. The ground level roads were connected to the existing road network. It took 43 months to finish the construction.

Among the works needed to accommodate the Western Harbour Crossing, additional works such as utilities diversions and reprovisioning works for the control of public usage of the sea wall for cargo handling were also required. These were carried out early in the contract to make site areas available. A new footbridge was erected over the existing Connaught Road West.

2. Tunnel Approaches

The tunnel approach roads were built on an area of reclaimed land which had been built mainly by public dumping over the years. This area was bounded on the north by the harbour and on the south by the existing Connaught Road West. The area presented constraints for the road layouts, but these were overcome by a horizontal alignment meeting the required design criteria.

3. Cut-and-cover Tunnel and Sai Ying Pun Ventilation Building

To accommodate the climbing lane in the southbound tunnel, the 350 m cut-and-cover tunnel was designed to curve to the open ramp. The open ramp then connected the cut-and-cover tunnel to the road networks in Hong Kong. The Sai Ying Pun ventilation building was located close to the edge of the harbour sea wall. It marked where the tunnel construction method changed from cut-and-cover to immersed tube units. The ventilation building housing 18 reversible axial fans was built on top and linking up between the cut-and-cover tunnel and the immersed tube unit. Ventilation of the cut-and-cover tunnel was from overhead ducts formed below the roof slab by suspending precast concrete panels.

4. Immersed Tube Tunnel

The immersed tube formed a straight alignment between the two ventilation buildings on each side of the harbour. The 1.36 km tunnel was made up of twelve immersed tube units, each 33.4 m wide, 8.57 m high and 113.5 m long. The average weight of one unit was about 35,000 tonnes. Each unit had two side ventilation ducts and two three-lane carriageway tubes. The twelve units were cast in three batches in a dry-dock casting basin at Shek O on the south side of Hong Kong Island. Four units were cast at a time and once completed were floated out to a temporary anchorage at Tseung Kwan O to be fitted for sinking. This procedure allowed the casting basin to be pumped out and made ready for the construction of the next batch of four units.

Construction of the first batch four units started in June 1994 and they were floated out in January 1995. The first unit was sunk into position adjacent to the Sai Ying Pun ventilation building in March 1995. The final unit, No. 11, was sunk into position at the end of April 1996.

The units were placed in a dredged trench, backfilled with general fill and then protected by a rock blanket 2 m thick with rock armour protection strips to prevent damage by dragging anchors.

5. Cut-and-cover Tunnel and Ventilation Building at West Kowloon

The West Kowloon ventilation building, similar to that at Sai Ying Pun, gave the tunnel a strong visual landmark, standing as it did in isolation on a large expanse of flat reclaimed land. The cut-and-cover tunnel rose from below the ventilation building to the portal and open ramp. The open ramp fanned out so that traffic can access the toll booth.

6. Toll Plaza

A total of 20 toll lanes are provided, and the middle four are reversible giving the option for up to 12 lanes to be operated should traffic in one direction require added facilities. Up to eight lanes are provided with automatic toll collection, although only six are operational at present.

Two bus bays are provided at either side of the toll plaza and a pedestrian footbridge has been constructed to give access across the wide toll plaza area. The ground level carriageways link up with the West Kowloon Express about 300 m north of the toll booths at the project boundary.

7. Administration Building

The Administration Building is situated at the east side of the open ramp and adjacent to the toll plaza. The three-storey building in oval-shaped was built with the latest environmental design. A solar control feature has been fitted on all windows so as to reduce loading on the air conditioning systems and improve exterior vision.

Reference :

Thomas Telford Limited - Journals on Line. "Civil Engineering Special Issue : Hong Kong International Airport, Part 2: Transport Links / November 1998 - Paper 11526 Western Harbour Crossing, Hong Kong - a successful BOT model"