Project-specific A-frame dredger deployed during construction of a parking garage under the Singelgracht canal in Amsterdam

Right under the Singelgracht canal, in the center of Amsterdam, Mobilis is building an underground parking garage for the municipality of Amsterdam: the Singelgracht-Marnix garage. An ambitious project for which Voorbij Funderingstechniek was asked to build the foundations. 

The installation of the grout anchors on the bottom of the Singelgracht releases grout which, of course, must be removed. For this, Bell Dredging was called in. "After a one-week trial, in which we showed using a self-developed A-frame dredger that we are able to remove the grout in this way, we received the final order," says Luca Stoop, rental manager at Bell Dredging.

Self-sufficient A-frame dredger

"In just three weeks we developed a completely autonomous A-frame dredger for this project. It consists of three pontoons where in the middle at the front is the A-frame from which our Bell 100 dredge pump hangs. Also the power pack (to drive the pump) and the water jet pump (to jettison the material from the bottom) are located on the pontoons. Only one operator is needed to control the dredger." Stoop explains that the dredger is in the water and attached to the sheet piling with a wire from each corner, allowing the dredger to propel itself on the water like an ice skater.

Inner-city challenges

"Using cables, we lower the pump and the material is sucked away from the bottom quickly and efficiently, without damaging the grout anchors in the process." Bell Dredging then dumps the released material into hopper barges (on water) that are sailed to the unloading site by pusher boats. "Less disruption, less transport and better for the environment: important factors in an inner-city project and for the municipality of Amsterdam." Stoop concludes, "We are proud to have responded quickly and adequately to the request and to have provided project-specific solutions, thus making a nice contribution to this fantastic project in Amsterdam."