Press

Combigolfe, Electrabel's¹ future combined-cycle gas turbine (CCGT) power plant, is not a typical project for DTP Terrassement, which is more used to the wide-open spaces associated with linear works. "Working on such a restricted site alongside a number of other companies, with a high density of equipment, requires perfect coordination between the different teams and impeccable responsiveness on our part," explains Matthieu Longhini, site manager. DTP Terrassement's €22-million contract calls for it to install buried networks for potable water, demineralized water, oily water, wastewater, firefighting water and compressed air, as well as electrical networks (lighting and earthing). Ultimately, the 30,000 square-metre site, with its 900-strong workforce, will be criss-crossed by some 18,300 linear metres of buried networks. "We prefabricated as many pipes as possible to allow us to lay significant lengths in a single operation, thereby minimizing interference with other trades also working on site," says project engineer Pierre Richard.

Laying the seawater intake and discharge pipes for the power plant's cooling system is a key stage in the construction process. The installation of the seawater intake pipes - two pipes 2.2 metres in diameter and 260 metres long, sunk 11 metres below sea level - was a real challenge for teams from DTP Terrassement. The discharge pipe, meanwhile, comprises over 850 metres of HDPE² piping 2.40 metres in diameter, laid in 300-metre-long sections. Around fifteen cranes were required to handle each section.

Being by the sea makes things much more complicated too: "As soon as you start digging, you get your feet wet!" explains works foreman Serge Berjuin. This meant that site machinery had to be equipped with GPS devices with three-dimensional positioning capability, to allow operators to dig under water with zero visibility.

DTP Terrassement gained valuable experience, and demonstrated its capabilities for this type of project, by working with Alstom Power on the construction of the Cyclofos thermal power plant, also sited at Fos-sur-Mer, in 2008. "On the Cyclofos project, we learned what an industrial construction site on this scale meant for a turnkey power plant supplier like Alstom," explains Gilles Dolfi, Manager at DTP Terrassement's South-East France branch with responsibility for developing commercial relations with Alstom Power. "Our challenge now is to show that we understand their problems, and that we are able to adapt."

Thanks to lessons learned from the Cycofos project, installation of networks started at a significantly earlier stage at Combigolfe, to allow room for other teams to do their work once the networks were in place. "DTP Terrassement provided Alstom with a dedicated team and equipment as soon as the site opened, allowing the quality of the works carried out to be guaranteed, and ensuring compliance with ambitious scheduling milestones," confirms David Dewever, Civil Engineering Department manager at Alstom Power Centrales. As a result, a relationship of trust arose between teams from Alstom and DTP Terrassement, enabling the latter to propose solutions for the entire networks and earthworks project package. "For example, we suggested using HDPE piping for the water discharge pipe, resulting in time and cost savings for the project," says project engineer Éric Demenet.

Alstom Power is currently working on the design of new thermal power plant projects in France and Morocco. DTP Terrassement is already involved, at the call for tender stage, helping to devise the most appropriate technical solutions for each situation. "We can't take anything for granted, however. We have to keep working every day to show Alstom that we are their ideal partner," reminds Gilles Dolfi. 

The power generation market is a potentially attractive growth market for DTP Terrassement over the next few years, as the deregulation of the energy market in France encourages suppliers to develop and diversify their own production capacity. In addition, France's installed base of power plants will not always be capable of meeting electricity demand. "The power plant fleet will need to be supplemented and renewed in the next few years with increasingly efficient plants designed to offer improved environmental performance," adds David Dewever. This will certainly provide opportunities for DTP Terrassement to consolidate the strong relationship it has built with Alstom Power.

David Dewever, Civil Engineering Department manager at Alstom Power Centrales, explains.

"A combined-cycle power plant comprises a gas turbine and a steam turbine. The first turbine is driven by combustion of natural gas. The hot exhaust gases from this combustion are used to help convert water into steam via heat exchangers. This steam drives the second turbine, which is connected to a generator, thereby producing electricity. A combined-cycle plant thus produces more electricity, while optimising fuel utilisation."