On 4 August 2005, a technical seminar on Practical Aspects of Large Diameter Watermains Rehabilitation in Hong Kong was organised by the CV Division. The seminar aimed to introduce the watermains rehabilitation programme of the Water Supplies Department (WSD) and its associated practical design and construction issues. The speakers of the seminar were Mr T W Chung of WSD, Ir Ian Vickridge of Black & Veatch HK Ltd and Ir Simon Ngo of U-Tech Engineering Limited. Ir Fanny Lau was the Event Coordinator of the seminar.

Mr Chung started with an introduction on WSD's rehabilitation programme. As more than 3,000 km of watermains in Hong Kong were over 30 years old, WSD has embarked on a programme of replacing and rehabilitating these aged watermains in 15 years. Major contracts to rehabilitate approximately 300 km of mains were awarded in late 2003. Two further D&C consultancies to rehabiliate approximately 250 km of watermains were awarded in early 2005 for completion in 2009. 

Ir Vickridge reviewed the rehabilitation techniques currently used in the Contract No 19/WSD/02, which was commenced in 2003 and was scheduled to complete in 2007. The main techniques used for the rehabilitation of large diameter mains were Sewage Lining and Cured In Place Pipe (CIPP) and the main trenchless method used for pipe replacement was Horizontal Directional Drilling (HDD). The materials used in pipeline rehabilitation were mainly thermoplastics. The speaker also introduced other materials for rehabilitation and design considerations.

Ir Ngo presented the details of practical construction issues including the site constraints of using swage lining for 800 mm watermains at Tolo Highway, CIPP for 750 mm watermains Tolo Highway and HDD for 500 mm watermains at Jockey Club Road. The congested and complex underground utility services limited the space between utility services. High water tables, varied ground conditions and obstructions such as boulders and old sheet piles could cause difficulties when using HDD. Good traffic and environment management are required for complying with those conditions stipulated in the excavation permit such as restrictions on working hours, traffic lane closure and noise levels for working near residential areas at night.

The seminar was ended with a question-and-answer section. On behalf of the CV Division, we would like to express sincere gratitude to all speakers for their informative presentation.