While recent rain has taken immediate pressure off dams, the Western Corridor Recylced Water Project continues to play a key role in South East Queensland’s water supply strategy by creating a new source of pure water that is resilient to climate change and rainfall fluctuations.

By early next year, the project will have the capacity to produce up to 232 ML/d of purified recycled water. Water is already flowing to the region’s power stations and will soon become available to industry and agriculture, as well as provide drinking water supplies should the Wivenhoe system fall below a combined capacity of 40 per cent.

A network of more than 200 km of large diameter underground pipes, three advanced water treatment plants, storage tanks and pumping stations make up the Western Corridor Recycled Water Project. Sixteen of the world’s leading engineering, construction, project management and water services companies formed five alliances to construct the project, along the way employing thousands of specialists from more than forty countries and clocking up more than six million work hours.

Western Corridor Recycled Water Pty Ltd Chief Executive Officer Keith Davies says the project is globally significant.

“Plenty of pipeline innovations have been delivered and we’ve gained admiration and respect from engineering, industry and water bodies throughout Australia and the world,” he says.

“We’ve won nine highly sought after industry awards, including the 2008 ‘Water Project of the Year’ at the Global Water Awards and International Project of the Year from the Construction Management Association of America.”

Stage by stage construction

Because of its size and complexity, the project was delivered in stages. Stage 1A – construction of the Bundamba Advanced Water Treatment Plant and associated pipelines – was designed to secure CS Energy’s Swanbank Power Station’s water supply and take pressure off South East Queensland’s dams. Up to 20 ML/d of purified recycled water was delivered to the power station, with ‘first water’ achieved just 10 months after construction began.

Stage 1B involved delivery of additional water from Bundamba to Tarong Power Station and was completed in June 2008, just nine months after water flowed to Swanbank. The Bundamba plant can now produce up to 66 ML/d of purified recycled water and has already delivered more than 10 billion litres of purified recycled water to Swanbank and Tarong power stations.

Stage 2A involved the construction of the Luggage Point (66 ML/d capacity) and Gibson Island (50 ML/d capacity) advanced water treatment plants, and more than 80 km of underground pipeline. A further upgrade of Gibson Island doubled its capacity, bringing the project’s total capacity to 232 ML/d.

Pipeline alliancing

Three alliances were responsible for the advanced water treatment plants and two alliances – the Eastern Pipeline Alliance and Western PipelineAlliance–were responsible for laying pipelines and associated infrastructure. The pipeline starts at Luggage Point and Gibson Island advanced water treatment plants at the mouth of the Brisbane River, travels through Brisbane’s eastern and southern suburbs to the Bundamba Advanced Water Treatment Plant near Ipswich, then continues north to Caboonbah at the top of Wivenhoe Dam, where it taps into an existing pipeline to take water to the Tarong storage lake. Construction began late in 2006.

Eastern Pipeline Alliance

The Eastern Pipeline was constructed by an alliance of AJ Lucas, Transfield Services and GHD. The pipeline comprises 104 km of underground pipelines, ten pumping stations and seven balance tanks. It involved around 50 crossings of roads, railways and major waterways, including the Brisbane River. Pipeline construction occurred through a heavily built up area and was complete in October, with Premier Anna Bligh signing the final pipe to be laid. At present, further drought contingency works are underway.

The first section comprises 58.5 km of 1,086 mm diameter mild steel cement lined (MSCL) pipeline from Luggage Point and Gibson Island advanced water treatment plants to a major pump station at Bundamba, where it links with the Western Pipeline. The second section is 17.1 km long and transports treated wastewater from wastewater treatment plants in Oxley and Wacol to the triple pipeline section near Goodna. The third section is 9.7 km of triple pipeline from Goodna to Bundamba, with a combined length of 29.1 km.

Mr Davies says the triple pipeline was laid in a 9 m wide trench.

“One of the interesting elements of this triple pipeline is that you will see no right angle bends along its length, because of the impact of thrust on the pipelines.

“We used the triple pipeline because it provided significant economic benefits and reduced impacts on the environment and the community.”

Mr Davies says that an innovative practice used on the Eastern Pipeline Alliance was horizontal directional drilling (HDD).

“HDD was used to install up to 970 m of pipeline underneath sensitive waterways, including the Brisbane River and Bulimba Creek,” he says.

“In May, HDD was used to drill 700 m from one side of Brisbane River to the other, passing 20 m below the riverbed and steered to within 20 cm of its target on the other side.

“The alliance had to weld together about 700 m of special 660 mm diameter steel pipeline, before stringing it out on a continual length of rollers. The full length was then welded progressively, internally lined, externally coated and hydro tested prior to drilling,” Mr Davies says.

“Following the hydro testing, the tunnel was bored out in continual passes to the required diameter. The pipeline string was then pulled back through the tunnel, using a bentonite lubricant, in a delicate five-hour operation.”

Significant planning ensured the success of HDD. Geotechnical data was obtained to determine the most appropriate layer through which to drill, and to avoid obstacles such as power or gas lines. The results of formation testing determined the design depth for the crossings and the correct pipeline angle.

HDD delivered a number of benefits. It avoided the alternative of constructing 45 m deep shafts at either side of the river and building large platforms to support construction and storage. It also saved time and was environmentally sensitive; an important factor for the health of the Brisbane River and Moreton Bay. The result was a reduction in construction costs, enhanced workplace safety, reduced community impacts and improved environmental outcomes.

Western Pipeline Alliance

The Western Pipeline Alliance, consisting of McConnell Dowell, Abigroup and GHD, constructed more than 80 km of large diameter pipeline, two pumping stations at Bundamba and Lowood and two balance tanks at Esk and Lowood. Pipeline construction was completed in June 2008.

Starting at the Bundamba Advanced Water Treatment Plant, the 1,451 mm diameter MSCL pipeline travels north-west for 32 km to a 5 ML balance tank and pump station at Lowood. From here, the MSCL pipeline splits into two glass reinforced pipeline (GRP) sections. The first section is 1,000 mm diameter GRP that heads 48.5 km north to Caboonbah, via the Esk balance tank, where it links with pipelines supplying power stations at Tarong. The second 1,200 mm diameter GRP heads 16.4 km to Coominya, where purified recycled water will be released into Wivenhoe Dam once combined dam levels fall below 40 per cent.

Integral to the Western Pipeline’s distribution role was the correct configuration and placement of pump stations. The pump station at Bundamba uses both booster pumps and transfer pumps to send purified recycled water to the Lowood balance tank. The booster pumps take water from Luggage Point and Gibson Island Advanced Water Treatment Plants, while the transfer pumps deliver water from balance tanks on site. Two 1,540 KW booster pump motors and three 1,365 KW transfer pump motors power the pump station, with a standby motor for each pump set.

Pumps of this size place considerable stress on pipes and a key challenge for the Western Pipeline Alliance was to establish cost effective solutions to determine the most suitable pipeline thickness.

One of the key factors in determining pipeline wall thickness was assessing water hammer severity. The Alliance was able to determine water hammer severity by undertaking computational surge analysis. Different methods of surge mitigation were modelled and analysed to determine the most effective solution for surge pressure reduction.

“The simplest option proved to be the most successful and surge vessels and pressure relief valves were installed,” Mr Davies says.

“Installation of an inline non-return valve positioned mid-way along the pipeline reduced surge pressures, which minimised the risk of fatigue failure in the pipe.”

The Alliance was also known for its speed of pipeline construction, with more than 50 per cent of the pipeline being built in just six months and, on one day, a massive 1.52 km of pipe was laid.

“One of our most exemplary innovations was the Safety Box Robot– a trenching device that increased the speed of construction and improved safety for workers,” Mr Davies says.

“This device protected crews inside trenches from walls collapsing or falling rocks. It also cut down on excavation, improving pipeline corridor rehabilitation.”

Water for Queensland’s future

Now that construction phase is almost complete, change is occurring within the Western Corridor Recycled Water Project. Moving forward, Western Corridor Recycled Water Pty Ltd has been brought together with SureSmart Water (the Gold Coast desalination plant) to create WaterSecure, a sustainable water business providing new sources of pure water for the South East Queensland Water Grid. WaterSecure will soon have capacity to produce up to 357 ML of water, providing water security for the people of South East Queensland.