Cross-harbour water main, West Kowloon to Sai Ying Pun: the landing
Underwater temporary works where a new cross-harbour water main comes ashore: cofferdam bracing to −15.7 mPD, pile cutting below the seabed, and a dry welding caisson at −17 mPD.
- Year
- 2010 – 2011
- Client
- Penta-Ocean Construction
- Location
- West Kowloon seawall
- Status
- Completed
- Category
- Underwater & marine
Where a submarine water main meets the seawall, the pipe has to be pulled up a slope, guided into position and welded to the land section. At West Kowloon all of that happened underwater.
- Cofferdam bracing. Divers installed the walings and struts of the sheet-pile and pipe-pile cofferdam, from +1.9 down to −15.7 mPD, using steel sections from 305 × 305 × 97 to 356 × 406 × 393 UC, with guide plates, welded brackets and bolted joints.
- Pile cutting. Around each old pile, silt was airlifted from −20.0 to −21.4 mPD, about 9 m³ per pile, so divers could cut the pile 500 mm below the seabed.
- Dry welding caisson. A caisson with a turning roller sat at −17 mPD. It guided the head of the pulled pipe, was sealed around it and pumped dry, so the landing joint could be welded in the dry.
- Turning shaft. The roller shaft had its own installation, temporary attachment and removal procedures.
We also designed a debris screen gate for the works and ran CCTV along the seawall joints.
Drawings
