Renovating one of the four runways at France’s biggest airport, under live air traffic conditions: Colas and its partners rose to the challenge on runway 1 at Paris-Charles de Gaulle airport. Colas yet again demonstrated its capacity to effectively mobilize its teams and equipment to successfully complete this colossal project within extremely tight deadlines
September 2025. The grader operator brings his machine to a halt. The traffic light has changed to red. A passenger plane taxis slowly by just a few meters ahead. At two points on the runway, construction machinery gives way to aircraft jetting off to New York, Tokyo, or Dakar. Welcome to “Roissy” airport’s runway 1, which Colas teams are currently renovating, along with its 23 feeder taxiways and two engineering structures spanning the A1 highway and the high speed rail tracks, while aircraft continue to l and and take off from neighboring runway 3. In use since the airport first opened in 1974, runway 1 is normally designated for take-offs owing to its length. But this sum mer, planes have been replaced by excavators, dumpers, finishers and a host of other site machinery operating the length (4.2 km) and breadth (45 m) of the runway. Teams have 4 months to carry out a complete refurbishment, from the runway’s surface layer to the thousands of meters of utilities and networks buried beneath it.
Colossal Resources
Last March, Colas France and Tersen, were selected by ADP Group to lead the consor tium responsible for the project, working alongside consortium partners Bouygues Energies & Services, Spie Batignolles Valérian, JDC Airports and Iris Conseil.
“Organization is critical. The work is divided up into different sections along the entire length of the site, with specifically assigned teams: demolition, earthworks, networks, asphalt mixes, concrete, etc. There’s also a marking team, a safety officer and an environmental team. There are 450 people working on site every day, and up to 650 at the height of the project", explains Sébastien Pavard, ADP Center Manager from the Île-Saint-Denis profit center.
In total, around a dozen Colas entities from the Ile-de-France region are mobilized, alongside teams from Colas Grand Travaux France, responsible for asphalt mix and concrete batched of the project.
Reinforced Concrete
Job superintendent Rachid Ben Youssef and his team are applying concrete to one of the 23 feeder taxiways serving the runway. Mixes are not used on these sec tions; aircraft taxi directly on a 40-cm-thick concrete slab.
“Before pouring the concrete, which we make on site in a mobile plant, a grid of cages with steel dowels is installed with the help of a surveyor”, he explains. “This reinforces the structure.” Having been complimented by an engineer colleague for the concrete transition slabs his team had built in another sector, Rachid talks proudly about his previous experience: “I’ve already worked on airport projects, at Orly in 2018, and then Nice, Strasbourg, and Satory. I’ve got 14 years of experience working on major projects!”
And it’s this wealth of experience that is one of Colas' major strengths, with numerous airport projects around the world to its credit.
Drainage and Utility Networks: a Project with Hidden Depths
Crucial operations are also underway on either side of the runway. Beneath the 15-metre-wide verges, multiple under ground tunnels carry electrical and tele communications networks. The figures are mindboggling: 7,400 meters of new tunnels, and 220 kilometers of cables!
At regular intervals, these “pipes” run through drawpits, concrete structures designed to facilitate future network maintenance operations. A total of 800 new pits have been installed, with 700 existing ones upgraded.
In parallel, seven teams – around 50 people – have been working full-time on drainage operations, carefully installing sewers to carry away rainwater.
Gravity is used to ensure water flows away naturally. Guillaume Tuquet, Job Superintendent in charge of dry utility networks, highlights the excellent level of coordination between teams. “Operations overlap with each other and need constant adjustment”, he under lines. “The drainage and network teams have priority because they are operating underground, but they are still dependent on the other trades. We constantly need to adapt to each other, but our teams are experienced, making sure that operations run smoothly. It’s a well-oiled partnership!”
Being Prepared for any Eventuality
The asphalt mixes dictate the tempo of the project. Everything is geared to the application of the runway surface, on which aircraft gather speed for take-off. Three successive layers are applied to the existing concrete structure, uncovered by planing operations.
A structural mix containing up to 50% RAP is produced on site for the two lower layers. The asphalt concrete for the top surface layer is also produced in the two mobile asphalt plants on site. The application of this aviation grade concrete is a crucial stage in the project.
The major technical challenge here is to avoid any joints in the direction of aircraft travel. “That would create a weak point”, explains Laurent, Equipment Manager and Workshop Manager at Colas Grands Travaux France. “So the surfacing is applied in a single pass, by four 7.50 meter finishers advancing side by side. Four feeders supply them with asphalt mix, and backup equipment is also on hand in case one of them breaks down.”
The site has its own workshop to repair machinery as quickly as possible. It’s essential to always be prepared for every contingency in order to deliver a runway that meets the highest quality standards: the tolerance for runway leveling is just 5 mm.
Compliance: Constant Monitoring
Before the project, teams spent several months planning each stage in advance to make sure everything ran smoothly. “Teams spent more time preparing for the project than actually carrying it out!” emphasizes Carolina Dos Santos Mendes, Design Manager. “We spent seven months sitting round the table with eight compa nies, each with their own methods. The technical discussions were very productive, and an essential step for learning how to work together in an environment as specific as an airport.”
Project planners than went to work drawing up detailed plans, incor porating the various technical and regula tory constraints. “Geometric compliance — sticking to the dimensions, gradients and leveling defined in the execution plans — is crucial on a runway. Everything has to be perfect to guarantee aircraft safety. If the runway isn’t up to standard, it simply cannot LUNCH BREAK Every day, more than 500 meals are served to employees working on the project. open”, explains Project Planner Clément Dao, responsible for compliance during the construction execution phase.
With these solid foundations in place, quality control is based on a reliable and shared reference system. Each day, site super visors carry out visual checks or checks using measuring devices. The results are recorded in QuickConnect, which aggre gates all site data in real time. A mobile lab, set up at the site compound, conti nuously analyses the asphalt and concrete mixes. “What we call a mobile lab is actually a real, fully-equipped laboratory: half of the human and material resources of the Île-de-France Normandy region have been mobilized”, explains Nicolas Tricot, Head of the Technical Division.
It took a month of groundwork to identify the staging points, those key stages where each completed step needs to be validated before work can continue. Planned so as not to disrupt ove rall operations, these checks are supervised by industrial engineer Clément Delettre: “We share everything directly with the cus tomer. In the event of non-compliance, we find a solution together. This way of working helps keep us on track!”
A Virtuous Economic Model
In 2019, Colas had already completed a spectacular project for ADP at Orly Airport – a benchmark in its history. The Roissy project serves to showcase the Group’s airport expertise once again. Quality, anti cipation, cooperation, the very hallmarks of Colas.
There was also a strong focus on controlling CO2 emissions during the project preparation stage. Optimization of distances between suppliers and the construction site, on-site production of asphalt mixes, concrete and aggregates (using biofuels), water management, sor ting and recycling of materials (see page 13): every aspect of the construction site's carbon footprint is optimized. A renewable biofuel, used by more than 220 machines and heavy vehicles on the site, enabled an immediate reduction of CO₂ emissions by 60% to 90% compared with fossil fuels. Electric batteries were also deployed, notably to power the site facilities, repla cing traditional generators. Recycling is another key component of the project. A mini waste collection center recovers wood, plastic, metal, paper, and cardboard waste, which is then sorted and processed a few miles away from the airport. “Re-using as many materials as possible is the econo mic model of the construction project”, explains Stéphanie Leibovici, Tersen’s Environment and Materials Operations Manager. “Concretely, anything that can be recovered will be, via our Ecotri and Valormat platforms. And centralizing all the group's waste streams makes us even more efficient.”
In parallel, a number of “small” actions, which are not obvious in the overall carbon footprint of the construction site, form part of the approach: requesting environmental data from suppliers, reusable water bottles and cutlery for everyone, recycling cigarette butts, etc. Reducing the impact of our activities has become second nature for teams.
Because the success of this extraordinary challenge is down to the commitment of the people involved. For Project Manager Pierre Feurstein, “the project brings together a close-knit team of men and women from different entities, with complementary skills. They all share the same ambition, namely to pool their strengths and deliver an ambitious, meaningful, and exemplary project from an environmental point of view.”
The Roissy project once again illustrates the Group's capacity to deliver high-performance, sus tainable runways that meet the very highest safety and environmental standards. It also reflects Colas’ ambition to be a trusted partner, capable of addressing the specific problems of each of its customers. “We weren't necessarily the cheapest bidder”, concludes Alexis Sueur, Director of the Île Saint-Denis profit center, "but we secured the contract on the basis of aspects other than price, such as lowering CO₂ emissions. The trust placed in us once again by ADP Group is a testament to our technical expertise and our commitment to providing sustainable and ambitious solutions.”
The Dispatch Headache
On the Roissy construction site, equipment management is centralized. With the support of the Equipment Performance Department (EPD), all the machinery requisitioned for the site — equipment belonging to Colas and its consortium partners, as well as rental equipment and hauliers’ trucks — are carefully tracked and allocated from the main site base.
In total, nearly 200 individual pieces of equipment have been inventoried for the project, each needing to be in the right place at the right time. In parellel, maintenance scheduling and repair planning in the site workshop are meticulously anticipated to ensure continuous equipment availability. Thanks to a meticulous monitoring system, each vehicle has a unique number that allows its movements and fuel consumption to be tracked.
Every day at noon, dispatchers meet with around thirty site managers from the consortium to adjust the schedule for the following day and plan for the week ahead. Equipment transfers from one work zone to another are carried out by two transport trailers, ensuring the constant flow of machinery essential to the project’s success.
Existing Materials Reused on Site
Deconstruction material is not waste on a jobsite. At Roissy, 76% of planed and excavated materials are recovered and used on site. The remaining 24% “waste” materials are sent to Valormat recycling platforms within a radius of 30 km.
Milled mixes from the existing runway are processed to be incorporated into new mixes: 20% in the surface layer, 50% in the intermediate layers. The demolished concrete slabs are a valuable raw material with many uses: sand, gravel and drainage stones are produced by the mobile crusher installed on site.
In its bid, Colas also proposed a variant for each end of the runway, previously covered with asphalt: a honeycomb structure filled with recycled materials from the construction site, covered with a mixture of earth and stone produced on site. The result? More than 1,000 tons of carbon saved and an area of 11,000 square meters that’s now permeable.
