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Relocation of Sha Tin Sewage Treatment Works to Caverns

The drill and blast method is the most commonly used method for hard rock excavation, both in Hong Kong and overseas. It is very safe and effective. The method has been successfully utilised for the construction of numerous projects like tunnels, shafts, rock caverns, and many underground MTR stations located in rock, including Quarry Bay, Tai Koo, Fortress Hill and North Point.

Merits of the Drill and Blast method:
Low noise generation
No continuous vibration
Safe and proven technology
Can suit different cavern layouts and configurations
Allows much faster progress and thus shorter works duration

Blasting Works and Their Control
Blast door

Blasting works for the caverns will be carried out at significant depths of 80 to 300m beneath Nui Po Shan, and will be enclosed by blast doors to ensure safety as well as mitigate noise. The tunnel ventilation system will be provided with built-in filters for dust removal. Blasting analysis indicates that noise and vibration at the nearby residential areas and other development due to the blasting will be minimal, and that the daily activities of the public will not be affected.

During the course of construction, DSD, our site supervisory staff and contractors will maintain close liaison with the nearby residents and stakeholders. Through stringent control measures, we will ensure effectively that the works will not affect the structural integrity of nearby buildings, and minimise any effects of the works on the neighbourhood.

Safety Precautionary Measures

Use of Explosives
The use of explosives is governed by the Dangerous Goods Ordinance and subject to stringent control by the Mines Division of Civil Engineering and Development Department (CEDD) with input from Fire Services Department and the Hong Kong Police Force.

The explosives used in construction requires a detonator to initiate before it can go off, hence is extremely safe. Detonators are kept and transported separately from the explosives. Cavern blasting works will be carried out within an enclosed environment, which further enhances safety in addition to minimising noise and dust impact.

With the "Blasting Duo", blasting works are well-controlled and safe.

Blasting works proceed in cycles. The blast itself is very fast, not exceeding a few seconds at most, while a blasting cycle takes about 16 hours. We expect there will be 1 to 2 blasts per day at each works front.

Blasting Operations
Blasting operations will only be carried out by registered shotfirers possessing a valid Mine Blasting Certificate issued by the Mines Division of CEDD. The operations will be carried out under close supervision of Blasting Competent Supervisors who are well experienced in blast design and blasting works.

We will keep the neighbourhood abreast of blasting information:
A blasting schedule will be issued at least one week prior to the commencement of blasting works
Signage displaying the blasting time will be erected near the works site on the day of blasting

Temporary Magazine
The Project involves the excavation of some 5 million tonnes of rock. To ensure that construction will progress efficiently, a number of works fronts will need to be deployed concurrently. To match this, a temporary magazine will have to be erected in the vicinity of the Project site close to the position of the ventilation shaft.

The magazine and its siting will have to be approved and licensed by the Mines Division of CEDD. We will closely scrutinize the storage of explosives and other operations to ensure compliance with statutory requirements, established standards and international best practices, such as the storage requirements of Explosives Regulations 2014 of the United Kingdom.

The temporary magazine will only store a small amount of explosives for a few days’ use. It will be removed as soon as blasting works are completed.

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