Technology at Arc 2000

In France, the well–known Arc 2000 winter sports centre is the home of a very unusual construction site. The plan is to establish the largest high–altitude reservoir in Europe. This lake, holding 400,000 m3 of water coming from melting snow, is to supply the entire skiable area with artificially created snow. For this unusual work site, the companies involved are leveraging the Trimble® GCS900 Grade Control System–for guaranteed precision, productivity and safety.

The l’Adret des Tuffes high–altitude reservoir at Arc 2000 is the largest in Europe. It is to store over 400,000 m3 of water coming from melting snow, in order to supply the entire skiable area with artificial snow. To achieve this, a consortium of companies must carry out 470,000 m3 of terracing in high mountain country, at an altitude of 2,200 m. The consortium includes Bianco (agent and subsidiary of Razell), Guintoli–EHTP (technical leader), NGE Group, Benedetti, SLEG, Carpi and their service providers Beolet, SFTP and Track TP. The work site possesses no fewer than about forty machines, as the work has to be finished before the first snow. In addition to this race against time there are other constraints, such as the difficulty of bringing heavy terracing machinery to the site of the work, and the varied and abrasive nature of the materials to be excavated.

Optimal Adjustment of Levels

This hard–to–reach work site is also very technical, since it requires the installation of a water–retaining system using a double geomembrane lining. The system will be protected by a containing layer of 30 cm of 10/30 material, and by another of 50 centimeters of 0/400 material. At this stage seven long–armed excavators will come on the scene, two with 14 meter booms and five with 18 meter booms. It’s a matter of adjusting the levels of the 60,000 meters squared of embankment, to give a slope of 33% over a length of 45 m. The two 14–metre long–armed excavators ? one Case 1199 and one Komatsu PC-210, have the responsibility for level adjustment in the strict sense. The others provide the material. To obtain the best performance, with optimal tolerance in the levels, the two excavators are equipped with Trimble GCS900 Grade Control system. "It’s the first time we have used such a system", explains Philippe Eccher, the chief surveyor with Bianco, which has had the benefit of logistical and technical support from the SITECH® Technology Dealer in France, Trimble’s premier provider of construction technology for heavy and highway contractors in France.

The Trimble GCS900 Grade Control System for excavators consists of two GPS/GLONASS antennas mounted on the back of the machine and rugged angle sensors fixed to the joints of the bucket, the arm and the balance beam. The antennas receive signals from both GPS and GLONASS satellites. Using the signals the antennas allow the operator to position the machine, in real–time and with maximum precision, on the digital plan of the work site. At any point, without pegs or any other external reference, the operator is aware of his position and knows instantly what finishing levels he must achieve. For this, the in-cab screen shows the movements of the arm, the balance beam and the bucket, thanks to the various angle sensors. "Even the movements of the tilted bucket are picked up", continues Philippe Eccher. This aid to driving brings greater safety because there are fewer people coming and going near the excavator to help the operator. In addition the GSC900 increases productivity, because the operator finds the right level more quickly, without having to make repeated passes. Finally, the precision of the Trimble GCS900 Grade Control System –+/–3 centimeters–guarantees that the correct levels will be obtained to provide economy in material and the integrity of the water–retaining system. "On this site, where we are working on top of a geomembrane, any movement that could pierce the water retaining system is strictly forbidden. By using the Trimble GCS900 Grade Control System for excavators means we have a lot less to worry about", the chief surveyor concluded.