CPG Consultants was engaged by PUB, Singapore’s national water agency, for the construction of the Kranji Stormwater and Abstraction Ponds.

The project involved the construction of an abstraction station and pond including part of the flyover at the Seletar Expressway/ Bukit Timah Expressway interchange, on a 1.8-hectare plot at Kranji. The project features the largest concrete water retention pond ever built in Singapore. It is unique as it is built under a flyover, within designated road reserve land to maximise land usage.

The pond is 170m long and 80m wide with a storage capacity of 84,000m&. It is designed to collect storm water runoff from the Sungei Mandai catchment basin via a 22m wide drainage channel upstream and a 4.4m wide drain downstream. During normal weather, water flows through these canals. However, during a thunderstorm, water is channelled into the retention pond for collection using a specially designed water intake system at the bottom of the canal. The water collected in the pond is then pumped to the Upper Seletar Reservoir.

The works for the flyover interchange involve the construction of 22 piers and 3 elevated roadways over the pond. The 14 piers within the pond will reach a maximum height of 28m.