Pioneering circularity in tunnel installations
‘Circular working is a new and challenging theme, but it’s also rewarding, we receive a lot of compliments,’ notes sustainable installations advisor Monique Dorresteijn. She is working on the Tunnel Renovations South Holland (PTZ) megaproject for Rijkswaterstaat.
‘We challenge contractors to work with reused materials. It’s always a quest to figure out how to make it happen.’ Pioneering circularity presents exciting opportunities, such as finding new uses for old tunnel cables, cameras, and ventilators.
Defining ambitions
Most tunnels in South Holland were built in the latter half of the 20th century or the early 21st century, making large-scale renovation necessary. For Rijkswaterstaat, this is an excellent opportunity to approach these renovations as sustainably as possible.
‘The majority of the renovation involves replacing all tunnel installations,’ explains Dorresteijn. ‘Circular solutions or reusing installations aren’t standard practice and provide new insights. It starts with setting clear ambitions for circularity during the planning phase.’
Learning and building on experience
The renovation of the Noordtunnel is still in the tendering phase. Once the contract is awarded, the project team will engage with the contractor to discuss sustainability ambitions. ‘We learn from every tunnel and apply those lessons to the next ones,’ says Dorresteijn.
‘For each renovation, we aim higher in terms of circularity. For instance, we’re exploring whether materials from one tunnel can be reused in another. The challenge is determining whether the installations fit and assessing their remaining quality.’
Starting early with circular design
A sustainable and circular design is the first step in reducing environmental impact. The project team uses 2 tools for this: sustainability requirements and the environmental cost indicator. ‘We don’t just ask contractors for optimizations; we also request a plan for the materials being removed,’ explains Dorresteijn.
Circular working begins early in the project with clear conditions. ‘You need to consider circularity for both the materials being removed and those being installed,’ she adds. Her experience shows that the greatest environmental benefit comes from reusing installations.
‘To achieve this, you must specify the reuse requirements to the contractor early in the project. This means determining the condition of the materials before the renovation begins, during the exploratory phase, to prevent them from ending up in the recycling bin.’
Modular cable systems
Tunnel renovations involve removing hundreds of km of copper cables. ‘Finding an application for these cables and avoiding the need to reinstall the same kilometers of cables was a challenge,’ says Dorresteijn. ‘We achieved a breakthrough with a different approach.'
'Instead of 1 main connection for all installations, we opted for multiple connection points. This allowed us to build modularly with the existing cables, reducing cable usage by 30 to 50%. We’re proud of this achievement.’
Avoiding unrealistic expectations
Dorresteijn aims to encourage not just contractors but also all market players to supply circular materials in future tenders. ‘This is complex, as we need to account for various safety considerations. Building incentives into contracts is difficult, and you have to avoid asking for the impossible. What works well is going through all the steps with the contractor early to determine what can and cannot be discarded.’
Cameras and tunnel ventilators
The goal is to reuse as many materials as possible, preferably in high-value applications. Materials that cannot be directly reused are disassembled and recycled. For some installations, the challenge is greater, especially with outdated systems that are hard to repurpose for tunnels with strict safety requirements.
‘For example, we have 150 cameras and 10 tunnel ventilators,’ says Dorresteijn. ‘We don’t yet have a solution for them. If materials aren’t assigned to the contractor, we have to take them to a recycling company ourselves. However, contractors might be able to reuse items like cameras or computer cabinets in other projects. It’s a complicated issue, and we’re still exploring the best approach.’
Open exchange of ideas
The Centre for Underground Construction provides valuable knowledge about new applications. Dorresteijn observes that experts from contractors and engineering firms are increasingly exchanging ideas freely.
‘It’s still about pioneering and discovering for ourselves, and that makes our work so enjoyable. The project team draws a lot of energy from this and we receive plenty of compliments.’