Mastering water - Steve Skinner reports on some of the world’s largest projects

Bypassing, harnessing or resisting the world's rivers and seas represents a unique challenge. Steve Skinner reports on the needs and solutions behind some of the world's largest and most spectacular construction projects.

Be it a natural energy source, a challenging obstacle or a menacing threat, water is a central theme linking many of the world's great structures.

Currently under construction in the Brazilian rain forest is the Santo Antonio hydroelectric power plant that will boast a generating capacity of 3.15 GW once completed in 2012.

Being constructed by a Construtora Norberto Odebrecht and Construtora Andrade Gutierrez joint venture, ground was broken for the the BRL $ 13.5 billion (US$ 7.7 billion) facility in September last year following four years of delays over environmental issues.

"Environmental protestors claimed the plant's reservoir would flood a vast area of the Amazon Rain Forrest, causing irreversible damage to the region's ecosystem," said Augusto Filho, equipment manager at Construtora Norberto Odebrecht.

"In reality, the facility will operate off the river system so there is no need to create an enormous reservoir for the accumulation of water. As such the maximum difference in water height between upstream of the dam and downstream will be 13 m," he said.

"A gap of this order is equivalent to a flooding only slightly above that caused during the rainy season in the region, so there will be no more ‘destruction' of the forest than occurs naturally," confirmed Mr Filho.

Dam

Excavation for the project involves the removal of 54 million m³ of material including 16 million m³ of pink granite, while construction of the dam will require 138000 tonnes of steel rebar and 3.5 million m³ of concrete.

Nine Atlas Copco D7 drilling rigs and two D3 models are currently being used on the project along with 22 electric compressors, five portable diesel compressors, two breakers and more than 50 manual hammers, all supplied by Atlas Copco.

The preference for Atlas Copco equipment is based on a 40 year relationship between Construtora Norberto Odebrecht and the company according to Andre Lima, the civil engineer responsible for work on the right margin of the Madeira River.

He said, "Our relationship is based on trust, guaranteed performance and good personal relations. In practice, this means we are operating with new and reliable equipment, which is allowing us to meet schedule without downtime for repairs."

Thousands of kilometres Northeast of Brasil on the Greek-Bulgarian border in the Rhodopen Mountains, Doka formwork is being used on another hydroelectric project in the shape of the 190 GWh Tsankov Kamak hydro storage dam.

The double curved concrete dam will be 130 m high and span 460 m at its crest. Tapering from 28 m thick at its base to 9 m at the top, the dam is being formed without time-consuming adaptations thanks to Doka's high-load dam formwork, designed specifically for this type of application.

"Time and cost pressures are decisively important criteria, particularly on large-scale projects in the energy infrastructure sector," said Josef Kurzmann, CEO of Doka Group.

"We are able to supply formwork and engineering know-how to ensure smooth progress across energy sector projects from wind farms, through cooling towers to hydroelectric dams, as with the Tsankov Kamak project," he said.

Barrier

While dam projects create barriers to store water as an energy resource, the need for water defences to protect man and industry represents a massive opportunity according to Piet Dircke, director of global water management at Arcadis.

"We see the market for water management in delta areas growing steadily, not only as a result of climate change, but also through an enormous increase in economic activity and population growth in these areas.

"The expectation is that by the middle of this century approximately 70% of the world's population will live in delta areas," Mr Dircke told iC.

Along with the US Army Corps of Engineers, Arcadis designed the Gulf Inter-coastal Waterway West Closure flood barrier (GICWWC) and Lake Borgne flood barrier, now under construction to protect New Orleans in Louisiana, US.

Following Hurricane Katrina in 2005, New Orleans expects to have an operable level of storm protection by June 2011 as a result of these two projects.

"The barriers have to be in place by the 2011 hurricane season," said Dennis Kamber, senior vice president of global water management at Arcadis. "We then envisage the whole project being complete by the end of 2011."

The GICWWC is a US$ 1.2 billion project, financed by congress and being undertaken by a Kiewit led joint venture. The project has four aspects, including what will be the world's largest pumping station, which will take all the interior drainage from the enclosed area and pump it out to sea.

"The pumping station will protect some 250000 residents as well as industrial areas," said Mr Kamber. "It's over 183 m in length and features 13 diesel engines driving 13 separate pumps. With each engine producing 3730 kW, the combined power output is some 48490 kW!

"Theoretically, the pumps could fill an Olympic size swimming pool in less than four seconds, with a rated value at full capacity of 56.7 m³ per second," Mr Kamber told iC.

Other aspects of the GICWWC, which sits just below the confluence of the Harvey and Algiers canals, include flood walls, levees and two navigable flood gates.

On the east side of the Mississippi River, the Lake Borgne flood barrier is concurrently under construction by Shaw Environmental and Infrastructure. Mr Kamber told iC, "This project represents the largest design-build contract ever awarded by the Corps of Engineers.

"With Hurricane Katrina, water levels rose by 7 m and the winds pushed the surge up to Lake Borgne and beyond. The barrier here is designed to knock down that surge."

The 3.2 km flood barrier is being constructed using 1.7 m diameter concrete piles, sunk to over 30 m and then capped.

While the projects in New Orleans represent a significant step into the US market for Dutch based Arcadis, Mr Dircke is already at the forefront of a debate over flood protection for New York City.

"New York needs a delta plan," he told iC. "Currently, the city is completely unprotected and a storm surge of 3 m would find up to 10% of it under water, affecting some 2 million people. The economic damage would be immense too. Wall Street would be out of business for weeks and most of the infrastructure, such as the metro, would likely be decommissioned for months," he said.

"There is time to address this as the risk is rising gradually, but I believe flooding in the future is inevitable. In the long run, New York will need flood barriers... I don't see any other way in which the city could be protected," said Mr Dircke.

Bridge

While dams and flood defences represent two key areas for mega-construction projects, many of the world's most spectacular and even iconic structures are bridges.

The 1.6 km Stonecutters Bridge in Hong Kong connecting Tsing Yi with Stonecutters Island is just one of a number of major projects currently under construction. Due to be completed this year, the bridge will carry the Route 8 motorway connecting Tsing Yi with Cheung Sha Wan.

The central span of 1.01 km is constructed of 65 deck units made from steel, the last of which was lifted into place in February this year. The complete deck weighs 33500 tonnes, while the 224 stay cables constructed from 451 galvanised 7 mm diameter wires weigh a further 7000 tonnes.

A spokesman from consultant Halcrow said, "Due to Hong Kong's sea trade, the bridge deck is suspended at a height of over 73 m to create a navigation channel capable of accommodating the world's largest ships."

Across in South Korea the Busan-Geoje crossing is under construction and remains on schedule for a December 2010 opening. Don Fraser of Halcrow, the construction adviser to lead contractor Daewoo Engineering and Construction, told iC, "As of October, and following the summer stoppage for the typhoon season, over 71% of the bridge work is now complete."

The Busan-Geoje crossing is a US$ 2.2 billion project combining a 3.7 km long and up to 48 m deep road tunnel with two cable-stayed bridges spanning 4.5 km. The bridges are, in the main, being constructed with precast sections because the facility was already in place for the tunnel work. Furthermore, the method allows more work to be undertaken away from the severe open sea conditions of the Pacific Ocean.

According to Mr Fraser, "Working on-shore gave better protection from the weather and sea conditions and enabled better quality control than could be achieved through in-situ pouring.

"That said, the main pylons are too big and complex to be precast and are being constructed using Peri formwork."

The towers are tapered outwards beneath the deck and then back inwards with a slight curve before straightening for the cable anchorage points. Five Liebherr 290HC12 tower cranes are in place on the towers for general bridge works.

"The tower shape is for both aerodynamic and aesthetic purposes," said Mr Fraser. "The shape echoes the traditional Korean curved roof, but it has meant setting out work has been more difficult than usual," he said.

In Florida, US, the Department of Transport has now finalised designs for the replacement of the Max Brewer bridge over the Indian River. Construction started in May and the 977 m long fixed span replacement is scheduled for completion in the spring of 2011.

The US$ 45 million design-build contract was awarded to Lane Construction and DRMP who in turn selected Pile Splices for the foundations and piling work. The fixed span bridge requires 64 large square concrete piles up to 55 m in length, each measuring 0.9 m x 0.9 m in diameter, to support the main span.

The company is using an APE D-125 diesel hammer to drive the long spliced concrete piles following the results of test piles driven earlier this year by GRL Engineers. GRL performed dynamic load testing across the location and developed the driving criteria for the production piles.

The company is also conducting dynamic load tests on every production pile to verify the load bearing capacity and confirm the structural integrity of the driven pile and splice.

Prospects

As both population and industry expand, the demands on infrastructure will inexorably lead to more giant structures. This, along with the ever growing threat created by global warming, means the possibilities for large structures to tame, channel or bypass water remain almost endless.

As Mr Dircke told iC, "I think the increasing flood risk is an opportunity for the western world to develop high tech solutions and sustainable ways of dealing with climate change in the future. It's a very exciting time."