Going under ground

25 April 2008

A forest of cranes at Razel's € 500 million Isséane incinerator project on the banks of the Seine on

A forest of cranes at Razel's € 500 million Isséane incinerator project on the banks of the Seine on the outskirts of Paris

Each year the amount of domestic waste generated in Paris equates to 500 kg per person. To deal with more than 500,000 tonnes of this a year the Isséane domestic waste processing plant is under construction on the banks of the river Seine south west of Paris.

Main contractor heading the joint venture to build the plant is the 125-year-old French specialist Razel, known for its expertise in earthmoving. Other main contractors are Bilfinger & Berger, Demathieu et Bard, SEFI, Soletanche, SPIE and Urbaine de Travaux. There are 55 contractors in total on the project.

Bordering the jobsite and boxing it in are roads at each end, a railroad on one side, and a road and the river Seine on the other side. A nearby heliport also has implications for the tower cranes on site. The river, while important as a means of transporting spoil and materials, presents problems in that the site, the foundations of which go down 70 m below ground, needs constant de-watering.

Restricted site conditions present challenges for all aspects of the construction and the complicated logistics took a long time to work out, explains Patrice de Ré, in charge of cranes and other equipment on site for Razel. Space is severely limited on the 400 x 100 m site with no room for materials storage so everything has to be delivered in the right sequence, just in time, and placed at the point of use as soon as possible using a selection of lifting equipment.

Doing the lifting

Cranes on site are a mix of top slewing saddle jib tower cranes, large crawlers and mobile telescopics on long- and short-term rental. The cranes are placing structural steel, for example, 30 m, 30 tonne stanchions, rebar assemblies, and the plant's furnaces and other equipment.

The 98 tonne furnaces were transported to site by boat from where they were built in Croatia. In late January, during the early stages of phase two, this machinery was being installed using heavy lift crawler cranes. It took two days to install the two furnaces, the catalysers and the conveyors.

Sarens, headquartered in Belgium, is contracted for all heavy transport on site and crane works during the industrial assembly of the waste incineration plant, explains Paulo Goncalves at Sarens France. People handling the work on site from Sarens France include a project manager, a site supervisor, four lift supervisors and six riggers.

Goncalves explains that the biggest challenge is to make all the lifts in the presence of the tower cranes overhead and the 400 people working on the confined site. In addition, most of the lifting work takes the loads below ground so lifts are controlled using instructions by radio.

For the heavy lifting work Sarens has on site one each of the following lattice boom crawlers; a 400 tonne capacity Liebherr LR 1400 in SDBW configuration with 70 m boom, a Liebherr LR 1350 with 54 m boom, and a Hitachi KH 500/3 with 34 m boom.

Sarens' telescopic boom wheeled mobiles on site are: a 300 tonne capacity Liebherr LTM 1300 for unloading the heavy plant equipment delivered by boat to the quay; a 160 tonne capacity Liebherr LTM 1160/2; an 80 tonne capacity Demag AC 80; and a 50 tonne capacity AC 50. These cranes will be on site for around 18 months while a 650 tonne capacity Demag AC 650 is brought in for specific lifts.

Also on site in mid-January was a selection of other mobile cranes, including a pair of Grove all terrains and a three axle Tadano Faun.

At the time of writing in late January there were three tower cranes on site but there will be eight in total at various times between October 2005 and November 2006. Largest will be a Liebherr 550, rented from Hexagone, with 60 m jib where it will pick 6.2 tonnes. The remaining cranes are Potains – three MD 345s (one with 50 m jib and two with 60 m jibs, one rail mounted), three MD 265s (with 55, 50 and 45 m jibs) and an MD 238 with 55 m jib. Tallest of the towers, with an underhook height of 61.5 m (to the level of its base, which is 5.5 m below ground), is one of the 60 m-jib MD 345 Potains.

Employed on the tower cranes are SMIE anti-collision systems, wireless wind alarms, computers for calculation and monitoring, and air beacons (there is a heliport close by). The AC30 anti collision systems have wireless connections, which avoid downtime caused by site damage to cabling. In addition to protecting against collisions between the cranes the system also manage prohibited zones over the site's neighbours.

For the transport work on site Goncalves says Sarens has 4 x 4 lines of Kamag SPMT with longitudinal connector beams. On the subject of transport, some of the rebar cages were too big to be made off site and transported in so they had to be made on site.

Under ground

An impressive part of the project is the fact that the building can be described as being like an iceberg in that most of it is below the surface. The deepest part of the building is 31 m below grade and the foundations go to 70 m. Walls to 50 m below ground are made from 95,000 m3 of concrete and 6,500 tonnes of reinforcing steel. Between the side wall and the river is 5,000 m of 30 mm diameter horizontally drilled steel ties.

Following 12 months of work, including driving 123 piles, Phase One of the project, which comprises all the work below ground, was completed at the beginning of 2006 and the second and final phase is now in progress.

A total of 600,000 m3of earth has been moved, a tenth of which was contaminated. It was planned that the top 3 m of soil of the former auto plant site would be de-contaminated but it had to be extended to 8 m.

Removing the spoil from site was done using a fleet of 50 tonne dumpers and then by boat, loaded from a temporary quay, built by Razel, via a specially designed chute system to break the fall from height of the spoil being loaded into the barges. Using the river saved an estimated 40,000 truckloads by road, according to Razel. At peak up to 5,000 tonnes – equivalent to 600 (15 m3) trucks – of earth a day was being moved out.

A major challenge was that earthmoving and pouring concrete were happening at the same time. The site record was 1,300 m3 of concrete poured in one day, the equivalent of 150 mixer trucks.

Contractor Razel's work on Isséane, the largest project in Paris, is on schedule for completion by June 2007. •

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