A9 Gaasperdammerweg

National Tunnel Standard

Our integral responsibility within the project encouraged creative solutions. For example, we widened the highway to five lanes in each direction and added a reversible lane. Over a three-kilometer stretch of the route, we built the longest road tunnel in the Netherlands: the Gaasperdammer Tunnel. This tunnel was the first in the Netherlands to be built in accordance with the National Tunnel Standard and is demonstrably safe and reliable. The engineering structures were also modified to accommodate greater traffic flows.

The tunnel has five tunnel tubes with a total of eleven lanes (2x3 local, 2x2 through and a reversible lane). The construction required 322,000 m³ of concrete, 47,000 tons of reinforcement, and 10,000 piles. In addition, more than 6,000 LED fixtures, 149 fans, and 535 emergency boxes were installed.

Part of the SAA program

In addition to the Gaasperdammer Tunnel, the project also included the construction of two new bridges as part of the SAA program (Schiphol-Amsterdam-Almere). These bridges replace the old ones to make room for the widening of the A9 to 2x5 lanes and a passing lane. Construction was carried out in phases: the southern bridge came into use in 2016, the northern bridge in 2020.

Huge prestressed box girders, supplied by Haitsma Beton, were installed for both bridges. The largest is 57 meters long, two meters wide, and weighs 230 tons. The bridge decks consist of five spans, with girders ranging from 23 meters for the shortest span to 57 meters for the longest. Normally, a box girder is 1.48 meters wide, but for this project, girders were made that are no less than two meters wide. Technical details include the use of HKP and HKV girders and post-tensioned transverse reinforcement to limit the construction height and maximize the clearance height.

The girders were transported by ship via the IJsselmeer, Markermeer, and Amsterdam-Rhine Canal and installed using large cranes, which significantly reduced construction time and disruption. Prefab girders shorten construction time and limit disruption; where possible, foundations from the old bridge were reused. The environment was also taken into account: noise barriers were installed and a new cycle path was created connecting Gaasperpark and Diemerbos, making recreational areas more accessible.

A good atmosphere, a good neighbor

With around 87,000 local residents in mind, the design team looked at how the surrounding area could be relieved as much as possible. For example, pile caps were used on the pile drivers to reduce noise pollution, vibration-free foundations were laid, construction roads were asphalted to limit dust and noise, and the Gaasp river was used as a transport route to avoid around 75,000 truck journeys. IXAS also considered opportunities to involve local residents in the project. In collaboration with Rijkswaterstaat, daily tours were given, a pop-up cinema was organized in the tunnel, and various open days were organized. A park of almost 2 kilometers has been created on the tunnel roof, connecting neighborhoods, and approximately 2,000 trees have been planted.

Sustainable solutions

Until mid-2038, the IXAS construction consortium will be responsible for the management and maintenance of the highway and the Gaasperdammer Tunnel. Because we want to do this as sustainably as possible, we opted for more than 6,000 LED fixtures in the tunnel and 394 light poles with LED lighting outside the tunnel. In addition, 15 kilometers of light-colored asphalt has been laid and 5,246 solar panels (good for approximately 2 GWh per year) have been installed at the end of the tunnel roof. This provides enough green electricity for approximately 600 households. Nature-friendly banks have also been constructed and materials have been reused as much as possible.