Desalination Plant. Something To Drink To

Major Metals Queensland has constructed large steel caissons, pivotal to the Gold Coast desalination project being built at Tugan.

Desalination works by separating salts from seawater using a reverse osmosis process. The new plant will produce 125 megalitres of drinking water per day by January 2009.

Major Metals Queensland manufactured two steel caissons for the GCD Alliance (the company commissioned to deliver the project). These will be used for the intake riser that collects seawater and the outlet riser that disperses the brine.

Both pipes were made from Grade 350 XLERPLATE® steel in 36mm, 40mm and 50mm thicknesses, and constructed in segments before being welded together and encased in concrete.

Manufactured In Sections

The intake riser dimensions are 3100mm in diameter and 66 metres long and it is manufactured in three sections of six, 24 and 36 metres. The outlet riser is shorter and manufactured in two sections of 18 metres and 36 metres.

"Our involvement with this infrastructure project was to use XLERPLATE® steel because it was an easily available material and fitted our design brief," said Major Metals Queensland General Manager, Ina Hirovanaa.

"Transport by Boom Logistics of these steel casings from Dalby to Pinkenba in Brisbane caused a bit of drama, especially travelling down the Toowoomba Range. They weighed up to 115 tonnes, so progress was slow and methodical."

By Barge

The caissons were then barged from Brisbane to Tugun and dropped into 20 metres of water around 1.5 kilometres off the coast, before being driven 40 metres into the ocean floor by a 100 tonne piling hammer. From there, the intake riser is connected to the desalination plant via a 2.8 metre tunnel which has been excavated around 40 metres below the sea bed.

The reverse process will apply to the outlet riser and tunnel.

More To Follow

In light of the continuing drought, the Queensland Water Commission has announced a range of measures for the state's water supplies, including a proposal for six more desalination plants.

It is predicted that almost one third of south-east Queensland's water supply could come from recycled water and desalination plants within 50 years.