Puzzling soil for inner-city densification

Inner-city densification can make an important contribution to the housing challenge in the Netherlands. But what is possible above ground is increasingly determined by what lies below ground. With its expertise in underground infrastructure, Aveco de Bondt supports governments and project developers to make complex inner-city developments possible. 

A great example can be found in Leiden. There, RED Company is developing three residential towers with a total of 580 homes. The towers are planned on the site where an outdated KPN office and a Monuta funeral home now stand. A matter of demolish and build? Well, it's not that easy, because under the ground is a tangle of cables and pipes. "Actually, the ground is as full as the city itself and that is structurally underestimated in densification projects," Richard Molemaker, K&L coordination specialist at Aveco de Bondt, points out. 

Underground challenges

The challenges in Leiden? In the immediate vicinity of the project are two high and medium voltage substations of TenneT and Alliander. Around and within the project area are therefore primary routes with 150 kV cables and 50 kV cables. These cables cannot actually be moved and are therefore normative for the design and implementation of developments in the plan area. Added to this are distribution routes, such as the enormous amount of telecom cables from the KPN power station. These cables and associated hardware and software can be adapted and relocated, but only after a new KPN power plant is built. Then you have the sewers and pipes for gas and drinking water. And furthermore, space is needed underground for, for example, a heat network, underground waste containers, tree roots, and safety distances and working space for management and maintenance of the underground infrastructure. All in all, this means you have to puzzle out the square meter, and that puzzle is becoming increasingly complex. 

Aveco de Bondt specializes in laying such complex puzzles. The engineering firm's K&L specialists regularly conduct studies and second opinions on underground infrastructure in inner-city environments. In Leiden, they also support project developer RED Company in communications, as well as providing process and project management to achieve a new layout of the underground infrastructure. 

Sheet piling vs. residential tower

"What you actually always do is identify bottlenecks that you then start to mitigate. For example, can you adjust the routing of a route? In doing so, you see that adjustments often have a knock-on effect," Molemaker says. "At LEAD, for example, we want to install a sheet pile wall to stabilize a nearby tunnel. That sheet piling is held in place with angled anchor rods. These anchor rods in turn clashed with the projected foundation for one of the residential towers. Therefore, in consultation with the architect, it was finally decided to narrow the base of the tower. Of course, this in turn affects the structure." 

It is precisely for such complex challenges that Aveco de Bondt is at its best, indicates business development manager Hilgard van Alphen. "A project like LEAD not only requires a lot of knowledge and focus on the subsurface, but also a broad view of the complete plan. You have to think inventively and integrally to solve those complex puzzles and be able to involve stakeholders in solutions. That combination is our strength."