The tropical island of Sulawesi is approximately 1,000km north of Australia and is one of the larger islands in the Indonesian Archipelago, the largest system of island groups to be found anywhere in the world. Located north west of the existing Batubesi Dam at Lake Towuti, the Balambano Dam is being constructed on the Larona River, the island's largest river. It is approximately 30km south west of the nearest population centre at Saroako, which is on the southern shore of Lake Matano.

The Balambano Dam is a gravity rolled and compacted cement [RCC] hydroelectric structure that is being built to supply additional energy to the expanded PT INCO [PT International Nickel Indonesia] major pyrometallurgical nickel processing plant at Saroako, where output is currently set to double to 68,000 tonnes a year. The electric power provided by the dam will reduce the sensitivity of the Saroako mining facility to the fluctuations in the world price for nickel.

Nickel was first discovered in the Verbeek mountains of Sulawesi in 1901 by a Dutch explorer conducting a study of iron ore in the region. However, it was not until 1966 that the full extent of the resources was recognised, and as recently as 1978 that commercial production started.

The dam is 90 metres high, with a crest length of 350 metres, containing some 546,000 cubic metres of lean concrete, with impermeability guaranteed by a PVC membrane installed on the upstream face of the dam. It is being constructed for PT INCO by Astaldi Thiess Joint Operation. PT Fluor Daniel Indonesia is project managing the work, while the design and resident engineering is being provided by Pacific Rim Power.

A 38 metre wide radial grated spillway is positioned mid way across the dam and around 45,000 cubic metres of conventional concrete was used in the construction of the spillway and power intake structure. Water is conveyed to the powerhouse by two five-metre diameter metal penstocks that are securely anchored to the downstream face of the dam. The powerhouse itself has two Francis Turbines with a combined capacity of 140MW.GETTING BACK ON TRACK.

When the joint venture contractors approached RMD KWIKFORM – by this time the original contractor, Astaldi, an Italian company with extensive worldwide dam building experience, had been joined by Thiess – the project was 18 months behind the original schedule. Time was clearly a precious commodity if new formwork solutions were going to be devised, supplied, implemented and supervised to get the project back on track. A task made all the more difficult by the distances involved and the sheer remoteness of the site.

Detailed designs – more than 300 to date – and calculations for the technically demanding spillway had first to be prepared and submitted for approval to Pacific Rim Power. This part of the dam was essentially divided into three elements; the flip bucket, the chute and the piers and abutments. The flip bucket consists of a large profiled concrete section that forms the “flip” to disperse water flow and the centre walls of the dam. The chute consists of the floor slab, side and centre walls and the crest of the dam, while the piers and abutments include trunnion blocks that support the radial gates.

On average, it took up to ten days to transport equipment from the company's base in Jakarta to the site. This involved loading onto barges in Jakarta for the sea crossing to Ujung Pandang, the capital of the island and its main sea port some 300km south of the Balambano Dam. Equipment was then unloaded before making what can only be described as the arduous trek by road to the dam construction site. So far RMD KWIKFORM has supplied 57 containers of equipment.
RMD Kwikform's work on site started in November last year and is now fast nearing completion, in line with the revised Astraldi Thiess joint venture programme that should see the dam fully operational by November of this year. Ultimately all of the RMD KWIKFORM equipment will make the return journey to Jakarta as, like so many RMD KWIKFORM projects around the world, the Balambano formwork is a hire contract.

Throughout almost the entire ten month programme RMD KWIKFORM has, as part of its contract, had two experienced formwork engineers supervising the safe and efficient use of the equipment.THE RMD KWIKFORM FORMWORK SOLUTION.

To complete the project against such a tight deadline, RMD KWIKFORM utilised a substantial quantity of three of its most versatile and successful systems. These were selected from a comprehensive product portfolio of internationally successful formwork and falsework solutions. Extensive use was made of RMD KWIKFORM Super Slim Soldiers, along with Alform aluminium beams and the Rapid Stage access and falsework system.

The project also called for the use of a wide selection of formwork accessories and the design and manufacture of special steel formwork for certain constructional elements. This included the off-site manufacture of 20 tonnes of special curved and shaped sections of formwork that were used to construct the pier and abutment nosings on the upstream face.

Super Slim Soldiers were chosen because of their ready availability, their high strength-to-weight ratio, and the system's ability to effortlessly accommodate complex geometric shapes. Available in nine standard lengths from 10mm to 3.6 metres, they incorporate webs that feature a series of holes along their entire length to allow the easy attachment of a host of accessories. Individual Soldiers can be bolted together to form longer members and adjustable node assemblies allow the Soldiers to be connected at any point along their length. Bracing is most frequently provided using adjustable Super Slim prop jacks or turnbuckles.
At the Balambano Dam, the Super Slim Soldier system was teamed up with RMD Kwikform's Alform beams, which were used as secondary members spanning between the Soldiers. They were also used to form plywood-decked platforms. These beams are noted for their strength and lightness and come with a wide selection of simple-to-use fixings. They incorporate timber infills to allow the easy fixing of the formwork facing.

Super Slim Soldier and Alform Beam wall forms were craned into position and were restrained using a range of sacrificial cast-in anchors and tiebars welded to the concrete reinforcement bars. Where necessary, special shear brackets were used to space the formwork off completed lower sections of the concrete structure. Super Slim Soldiers were also extensively utilised as support brackets and raking shores.

The facing to the Balambano formwork was also supplied by RMD KWIKFORM as part of its “total supply” solution. It was mostly either locally sourced plywood or, for certain applications, high strength plywood specially imported for the task from Australia. Steel facing was, however, used for the special pier and abutment nosings.

RMD Kwikform's modular Rapid Stage was used extensively for working access to the chute walls and pier abutments. The system was also put to work as temporary falsework on various parts of the project.

Rapid Stage was particularly suited to the project, bearing in mind the pressure to return the contract to schedule, as it is highly adaptable, reduces construction times and is renowned as being a particularly cost-effective solution. Indeed, Rapid Stage can even be used where projects involve complex multi-curve profiles that are almost impossible to support economically using less sophisticated systems.

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