Sungai Selangor Dam
Malaysia (2000 - 2005)
Impelled by Klang Valley and parts of Selangor’s population boom in the 1980s till the 1990s that led to the flourishing of major townships and commercial areas, the State of Selangor saw the pressing need for a viable clean water source in the state as demand was fast outstripping supply.
Answering the state’s call for a long-term solution, we came up with the comprehensive Sungai Selangor Water Supply Scheme Phase 3 project that detailed, among others, the 110 metre-high rockfill Sungai Selangor dam designed to store and regulate a maximum capacity of 235 million cubic metres of water.
This dam’s embankment is comprised of a layer of 0.62 million cubic metres of granular material. The dam, 400m wide at the base, 800m long and 110m high, is composed of 1.2 million cubic metres of clay core and 6.4 million cubic metres of granite. During low flow period, water from the dam’s reservoir will be drawn for release into the river to ensure sufficient raw water supply for the water intakes downstream.
At Gamuda, we believe it is equally important to serve the needs of the people and to protect our environment for the benefit of our future generations. Therefore, careful planning and efficient construction management was made to ensure the successful implementation of the project to minimise impact on the environment, during, pre and post construction.
Completed six months ahead of schedule, the Sungai Selangor Dam’s impoundment commenced 25 April 2003 and reached its full supply level at 220 metres (above sea level) on 13 April 2004.
For the dam to function effectively, it was designed and built with several key components :
The draw-off tower is a crucial and prominent structure of the dam, standing at a height of 110m with a diameter of 9m. This is the structure where water is drawn from the reservoir for release into the river (whenever discharges from the dam are required to augment low flows in the river), ensuring that sufficient water is available at the raw water intakes downstream. The twin discharge pipes leading from the draw-off tower have flow-measuring devices and flow-regulating valves installed to control and measure the volume of water released into the river. The draw-off tower has four service gates at various levels (RL131m, RL160m, RL190m and RL210m. Two emergency gates located at the beginning of the twin discharge pipes ensure that water discharges can be shut down whenever pipe maintenance is required.
The chute spillway with a flip bucket has a width of 30m and a length of 230.54m, which is for overflow during the wet season. It is designed as an open chute, discharging excess water over the crest of the dam. When water overflows into the spillway, it creates a waterfall-like scene at the downstream face of the dam. The spillway has a discharge capacity of 3000m³/sec (260,000 Mld), more than sufficient to route excess water during extreme floods.
The plunge pool, located at the lower end of the spillway functions as an energy dissipator to dissipate the energy of any overflowing water from the spillway before the water is allowed to rejoin the river. This is to prevent turbulence and erosion of the riverbed and its banks. The plunge pool is 196m long and is 4m deep.
The 480m long diversion tunnel was blasted through solid granite at the start of the construction to divert the river to facilitate construction of the dam. It is now used to house the twin 2200mm diameter discharge pipes coming out of the draw-off tower. The water drawn from the dam for release flows through these twin discharge pipes before being released into the river. The tunnel is 7m in diameter and has a horseshoe shape. It was constructed using the controlled drilling and blasting method.
The coffer dam is a temporary water-tight enclosure that was built to divert the river to enable work to be carried out in the dry for the construction of the main dam. The coffer dam is required during the construction of the main dam. The coffer dam is required during the construction phase but has no specific function after the completion of the dam.
The dam is a necessity as demand for water in Selangor and Federal Territory has outstripped supply and this is the last viable source of raw water. Apart from performing its primary function to regulate the flow in the river, the Sg. Selangor Dam is a man-made attraction which offers recreation and scenic view to the public at large.
Other components of the Sungai Selangor Water Supply Scheme Phase 3 comprise of:
- Two water treatment plants located in Rasa (250mld) and Bukit Badong (800mld)
- The realignment of Kuala Kubu Bharu-Bukit Fraser Road
- About 7.7km of the original KKB-Bukit Fraser Road was realigned and shifted to a higher elevation. The realigned road now comes with two new bridges, the Sg. Luit Bridge and the Sg. Selangor Bridge and rest areas. The new stretch of road skirts around the dam with a panoramic view of the entire dam and a backdrop of lush greenery.
- Relocation and resettlement of two (2) Orang Asli villages (comprising 84 families)
The Orang Asli villages were relocated and resettled at a cost of RM1 million. The two communities (Kg Gerachi and Kg Pertak) were provided with:
- modern villages and community facilities built within their old natural surroundings
- land planted with oil palms to replace their crop trees
- relocation allowance and financial compensation for loss of crops
- community development through skills training and jobs to help them sustain a livelihood
- welfare and healthcare service programmes
|Client||Selangor State Government, Malaysia|
|Concessionaire||Syarikat Pengeluar Air Sungai Selangor Sdn Bhd|
|EPC Contractor||Gamuda-KDEB-TSWA Joint Venture|
|Scope of Works||
Components of SSP3
Regulating dam over Sungai Selangor that entails:
Water treatment plants