Saturday 21 July 2012

Detention tank and diversion canal to ease Orchard floods

By Olivia Siong, Channel NewsAsia, 19 Jul 2012

It plans to build a diversion canal and detention tank at the Stamford Canal Catchment to better deal with intense storms.

Prolonged heavy rains led to major flooding at Orchard Road in the last two years.

This was due to the Stamford Canal exceeding its capacity.

PUB is implementing two new measures after a nine-month study.

Firstly, PUB plans to build a new diversionary canal to ease the load on the existing Stamford Canal.

Storm water at the upper catchment, which serves areas like Napier Road and Holland Road, will flow to the Singapore River instead of the Stamford Canal.

So the new two-kilometre long canal will run beneath the surface starting from Grange Road, along Hoot Kiam Road, River Valley Road and off Kim Seng Road to the Singapore River.

The diversion canal along Bukit Timah Road is one of two existing diversion canals in Singapore. It was built in 1991 and diverts storm water to the Kallang River.

The new diversion canal will be about one third the size of the one along Bukit Timah Road.

A new underground water detention tank will also be built at Tyersall Avenue near Holland Road, opposite the Ginger Garden.

The tank will be built below a proposed nursery and coach park, which will be built by National Parks Board.

The tank will collect excess rainwater from drains along Holland Road during a heavy downpour.

The water will then be pumped back to the drains and discharged after a rain storm into the Marina Reservoir through the new diversion canal.

It will be able to hold about 15 Olympic-sized swimming pools of water - that's about 38,000 cubic metres of water.

The tank will also be about four-storey high. It will be the second water detention tank in Singapore. The first was built and completed in 2002 at Opera Estate.

The new water tank will be two-and-a-half times the size of the existing one.

PUB said while the new measures might not completely eradicate flash floods, they will help alleviate the situation.

Director of Catchment and Waterways for PUB, Mr Tan Nguan Sen, said: "Whatever structural design you build, engineering design you have, if you have a storm that's 'higher' than your design, you'll still have some residual flood risk. But definitely it'll be much less extensive and much less severe."

Mr Tan added motorists might be inconvenienced during the construction of the diversion canal and detention tank.

"It'll be something like what you see in typical road construction or drainage construction. The traffic may have to be diverted temporarily and then reinstated later.

"We will have to work together with the other agencies to make sure there's minimum traffic disruption and to ensure the traffic will continue to flow as per normal," Mr Tan explained.

Detailed design for the construction tenders for both measures will be carried out in the second half of this year.

Work on the diversion canal is expected to be done by the end of 2017.

And the detention tank is set for completion by the end of 2015.

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