BMA puts huge drainage tunnel to the test

Labourers work around the lip of a shaft leading to a giant concrete tunnel which is currently being tested as it begins to take in water from six Bangkok districts on Monday. The system will be fully operational on Sept 6. (Photos by Apichart Jinakul)

Excess water in several key areas of the capital is being channelled into a giant underground tunnel to test a system that promises speedy drainage of floodwater, according to City Hall.

Bangkok governor Aswin Kwanmuang said yesterday the tunnel's capacity was being put to the test before the entire system begins operating on Sept 6. It is one of seven tunnels designed to ease the chronic flood problem which often paralyses the city during heavy downpours.

Rainwater from streets in six districts -- Dusit, Bang Sue, Phaya Thai, Chatuchak, Din Daeng and Huai Kwang -- was diverted into the tunnel which runs underneath Khlong Bang Sue. The tunnel will also receive water from the adjacent Khlong Lat Phrao which will help expedite the flow of excess water to be emptied into the Chao Phraya River.

Pol Gen Aswin and City Hall executives also inspected the water pump station which is part of the tunnel system in Kiakkai in Dusit district.

The Bangkok governor said the tunnel, which will cover the six districts, was taking water yesterday for the first time in a test run. It is estimated the tunnel will fill with water over two days before the water is pumped into the Chao Phraya.

Also to be tested is the control room that operates the tunnel equipped with a water pump capable of pumping 60 cubic metres of water per second.

There are also three facilities regulating water going into the tunnel in Ratchadaphisek Road, Vibhavadi Road and Khampaeng Phet Road.

The tunnel will be officially opened on Sept 6 and is likely to greatly alleviate flooding in a 56 square-kilometre area across the six districts, he said. (continues below)

A water pump facility has also opened and will operate in sync with the giant tunnel.

Pol Gen Aswin said water clogging major roads in key commercial zones will be drained faster when the tunnel becomes fully operational.

Particularly vulnerable to inundation are; Phahon Yothin Road, from Saphan Kwai intersection to Lat Phrao intersection; Vibhavadi Rangsit Road, from Sutthisan intersection to Lat Phrao intersection; Ratchadaphisek Road, from Ratchayothin intersection to Khlong Bang Sue; Lat Phrao Road, from Ratchada-Lat Phrao intersection to Khlong Bang Sue; Khampaeng Phet Road, from the Srirat Expressway to Chatuchak weekend market; and Samsen Road, from Khlong Bang Krabue to the Kiakkai intersection.

The governor said the tunnel will increase water drainage capacity in Khlong Bang Sue from the Phahon Yothing Road to Vibhavadi Rangsit Road. The water will be pumped through the five-metre wide tunnel which stretches all the way to the Chao Phraya.