Design

The Pearl River Delta is divided into two portions, east and west, with Guangzhou in the middle. Cities in the east, such as Hong Kong, Shenzhen and Dongguan enjoy bustling economic activities due to their direct or close access to major export infrastructure. But most cities in the west, including Macao and Zhuhai, have fallen behind in their economic growth. One of the reasons is their long travelling distance from world class container terminals in Hong Kong and Shenzhen. Although the east and west are separated by the Pearl River (max. width of 27 km), transportation from cities in the west to Shenzhen or Hong Kong usually takes more than six hours along the 125-km Guangzhou-Shenzhen Expressway as well as the 60-km Guangzhou-Zhuhai Expressway. A bridge providing a link across the estuary of the delta to Hong Kong will significantly shorten the journey time.

The two main engineering challenges will be the monsoons and the thick but soft seabed layer made up of river and marine deposits over the years.

The minimum depth of the fairway (navigation channel) is 10 m for ordinary ships up to 85,000 DWT (Dead Weight Tonnage) with under keel clearance of at least 0.5m from the seabed. Much deeper fairway of 13 to 15 m is required for ocean liners.

- Details can be found in the Coastal Engineering Technical Notes of the US Army Corps of Engineers

The western part of the Pearl River estuary is generally very shallow at a depth of about 5 m.

With the unique current circulation of the Pearl Estuary, soft river and marine materials tend to settle on the western portion of the delta. The annual sedimentation rate reaches 200 mm near Macao with only 5 mm in Hong Kong waterways. Such a big difference in deposit rate leads to the gradual silting up of the western part of the estuary. Water depth in some areas can be less than 5 m. In contrast, the main fairway (navigation channel) of the Pearl River is at least 20 m deep near Hong Kong.

Brief description of bridge design

There are several proposals for building a bridge with variations in their designs. There is also a proposal of building a tunnel linking Zhuhai to Shenzhen. One of the proposals put forward by Gordon Wu is a bridge approximately 10m above water, building upon the shallow seabed near Macao and allowing small leisure or fishing boats to pass underneath easily. The proposed bridge will be 32 m wide with 4 traffic lanes running in each direction for cars and trucks. For other proposals involving rails, trains will travel on a lower deck level like the neighbouring Tsing Ma Bridge. For the main crossing across the deep water fairway near Hong Kong, two alternative proposals have been made. There is a choice of either a tunnel or a high suspension bridge (62 m above water), enabling the passage of ocean liners. Though it will be cheaper to build a suspension bridge, frequent visits of tropical cyclones/typhoons in the summer requires careful design and more durable materials which can raise construction costs significantly.

In addition, exposed traffic on a high cable stay suspension bridge will be easily affected by heavy rain and high wind and thus pose more limitations upon using the crossing.

In forming his proposal, Gordon Wu made reference to two different bridges, namely, the Chesapeake Bay Tunnel-Bridge in the USA and the Oresund Bridge linking Denmark and Sweden.

Other proposals are more or less the same with the major difference being the landing locations for the crossing. (See Map) Gordon Wu put forward his proposal to his fellow professional engineers in mid-September and won overwhelming support from the Hong Kong Institution of Engineers (HKIE). Part of his proposal is to connect the bridge with the upcoming Shenzhen Western Corridor, recently committed by the Shenzhen and Hong Kong governments, in order to link up the cities on the east and west of the Pearl River Delta.