Drainage Services Department

Layout of Lai Chi Kok Drainage Tunnel

The $1.7 billion 3.7 kilometres long Lai Chi Kok Drainage Tunnel comprises a 2.5 kilometres mid-hill branch tunnel that runs from Tai Wo Ping to Butterfly Valley, and a 1.2 kilometres main tunnel extending underneath Lai Chi Kok’s urban strip to the coast. Connecting the two tunnels is a stilling basin. The Stilling Basin, a drainage reserve area underneath Tsing Sha Higway, was developed to a pet garden for recreational use. The piece of land reserves flood prevention, recreation and transportation triple purpose.

Stormwater runoff from a 290-hectare uphill area, north of Ching Cheung Road, is intercepted into the branch tunnel through 6 intakes installed along its length. Runoff from Butterfly Valley also discharges directly into the stilling basin. From this point, the main tunnel then conveys the combined flows to a coastal outfall near Stonecutters Island.

Construction works of Lai Chi Kok Drainage Tunnel were carried out on the urban fringe, reducing the need for road excavation in busy urban areas and minimising disruptions to the public, traffic and commercial activities. This interception scheme substantially reduces the runoff flowing onto the downstream and comprehensively alleviates the flooding risk of Lai Chi Kok, Cheung Sha Wan and Sham Shui Po areas.  The project commenced in November 2008 and was commissioned in October 2012.

Perspective Layout of Lai Chi Kok Drainage Tunnel

Confluence of Lai Chi Kok Drainage Branch Tunnel and an Adit

Main Tunnel under Lai Chi Kok Urban Area

Lai Chi Kok Drainage Tunnel Outfall

Lai Chi Kok Drainage Tunnel Equipment Enclosure

Located at the decked still basin, the Lai Chi Kok Drainage Tunnel Equipment Enclosure is the control hub of the tunnel's various mechanical and electrical equipment (including the tunnel communication system, closed circuit television, main tunnel overflow system, etc.). It is also equipped with the lively multimedia facilities introducing the causes of flooding and the flood prevention strategies in the urban areas of Hong Kong, enabling the public to gain a better understanding about the flood prevention work of the Drainage Services Department.

Lai Chi Kok Drainage Tunnel Equipment Enclosure (360° View)

Exhibit at Lai Chi Kok Drainage Tunnel Equipment Enclosure

Stormwater Harvesting System

Drainage Services Department incorporated the concept of sustainable development into the design of Lai Chi Kok Drainage Tunnel, installing Stormwater Harvesting System at Butterfly Valley Road Pet Garden. The water resources collected from the Tunnel catchment area are filtered and disinfected by chlorination, then can be supplied to Butterfly Valley Road Pet Garden for non-potable water uses such as toilet flushing, irrigation and cleansing. The designed capacity for Lai Chi Kok Drainage Tunnel Stormwater Harvesting System is about 120 cubic metres (equivalent to the volume of about 20 water tankers)

Stormwater Harvesting System

Stormwater Harvesting System

Stormwater Harvesting System

The Stilling Basin beneath Tsing Sha Highway with the Basin Deck being Developed into a Pet Garden

Situated at 2 Butterfly Valley Road, Lai Chi Kok, the Butterfly Valley Road Pet Garden shares the land of the stilling basin of Lai Chi Kok Drainage Tunnel. The land was originally reserved as a widely landscaped operation and maintenance (O&M) area. Drainage Services Department, through optimizing the operation and maintenance procedures and revising the landscape design, turned the operation and maintenance area of the stilling basin which was constructed under the viaducts of the Tsing Sha Highway, into a pet garden and enabled one piece of land to serve the purposes of flood prevention, transportation and recreation. This maximization of land utility follows the principles of sustainable development. The Butterfly Valley Road Pet Garden was handed over to Leisure and Cultural Services Department (LCSD) for management and was open to the public on 13 March 2014.

With an area of about 7,000 square metres, Butterfly Valley Road Pet Garden is the largest pet garden in Kowloon. It was decorated under the theme “Jumping on a Floating Piece of Wood” with a ripple patterned footpath and a raft-like wooden platform on the lawn against the backdrop of the drainage tunnel underneath. Various pet facilities include pet drinking fountains and playground equipment such as pipe play tunnels, weaver posts and jumping hoops. Moreover, rainwater collected by Lai Chi Kok Drainage Tunnel will be treated for gardening, toilet flushing and street cleansing, making the best use of the precious water resources.

Butterfly Valley Road Pet Garden (360° View)

Butterfly Valley Road Pet Garden (360° View)

Butterfly Valley Road Pet Garden (360° View)

Butterfly Valley Road Pet Garden

Butterfly Valley Road Pet Garden

Butterfly Valley Road Pet Garden

Butterfly Valley Road Pet Garden

Butterfly Valley Road Pet Garden

Butterfly Valley Road Pet Garden

Butterfly Valley Road Pet Garden

Butterfly Valley Road Pet Garden

Stilling Basin of Lai Chi Kok Drainage Tunnel

The 3.7 kilometres Lai Chi Kok Drainage Tunnel comprises a 2.5 kilometres midhill branch tunnel that runs from Tai Wo Ping to Butterfly Valley, and a 1.2 kilometres main tunnel extending underneath Lai Chi Kok’s urban strip to the coast. Connecting the two tunnels is a stilling basin.

Stormwater runoff from a 290-hectare uphill area, north of Ching Cheung Road, is intercepted into the branch tunnel through six intakes installed along its length. Runoff from Butterfly Valley also discharges directly into the stilling basin. From this point, the main tunnel then conveys the combined flows to a coastal outfall near Stonecutters Island. This interception scheme substantially reduces the runoff flowing onto the downstream and comprehensively alleviates the flooding risk of Lai Chi Kok, Cheung Sha Wan and Sham Shui Po areas.

The need for two tunnel segments of Lai Chi Kok Drainage Tunnel and a stilling basin stems from the project’s unique complexity. To reach the harbour, the main tunnel is aligned along Tsing Sha Highway, which is the only viable corridor without encroachment into private lots. This brings about a direct encounter with five railways, including two subterranean ones—the Tsuen Wan Line at a depth of 25 metres below ground and the Guangzhou-Shenzhen-Hong Kong Express Rail Link situated at 37 metres depth. The resulting design is a deep tunnel just below the Express Rail Link with vertical inlet and outlet shafts at each end.

Stormwater torrents carry a considerable amount of silt and debris. The stilling basin serves the primary function of calming the flow for debris settlement to protect the main tunnel from siltation. Stormwater collected from the branch tunnel will flow into the Stilling Basin. After stilling and sedimentation, the stormwater will then flow into 45 metres deep Main Tunnel Inlet Shaft.

As the still basin is constructed under the viaducts of the Tsing Sha Highway, Drainage Services Department, through optimizing the operation and maintenance procedures and revising the landscape design, turned the operation and maintenance area on top of the still basin into a pet garden and enabled one piece of land to serve the purposes of flood prevention, transportation and recreation. This maximization of land utility follows the principles of sustainable development.

Stilling Basin of Lai Chi Kok Drainage Tunnel (360° View)

Stilling Basin of Lai Chi Kok Drainage Tunnel (360° View)

Stilling Basin of Lai Chi Kok Drainage Tunnel