As part of the project undertaken by the Drainage Services Department (DSD) in Hong Kong to reduce the risk of flooding, Atkins developed a stormwater drainage system, which required three years of tunnelling design work.

According to DSD, the drainage tunnel forms an integral part of the overall flood control strategy for West Kowloon, Hong Kong, as the new system will capture surface run-off at six locations and discharge it into Victoria Harbour to help alleviate flooding in low-lying developed areas.

As a result of the drainage system, uphill flows are intercepted and the overall drainage ability is enhanced the overall drainage ability to cater for rainfalls over a one in 50 years return period.

However, as the two 4.9m internal diameter tunnels are located in an urban area Atkins said it was essential to ensure that design and construction work did not affect structures such as railways, viaducts and culverts, as well as high earth and water pressure.

Meanwhile, to ensure the lowest possible impact to the environment, a slurry-type tunnel boring machine was selected to drive within bedrock, mixed ground and soil over 40m deep and under high underground pressure.

Atkins deputy project manager Ray Chan, said: “The final breakthrough marks the successful completion of a highly complex and challenging tunnelling project for Atkins. The scheme presented a huge engineering challenge: constructing tunnels beneath densely populated areas and a dry shaft right next to the harbour, and contending with extreme earth and water pressure. Our deep geotechnical knowledge ensured that the scheme was capable of withstanding these challenges.”

Carys Matthews

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