Excavation of all construction pits at The Green Arch

Complex challenge successfully implemented

The excavation of the construction pits for the new A16 Rotterdam was an extensive operation full of complex challenges. With a total of 34 pits, some of which were highly specialized with closely spaced piles and struts combined with limited working space, the project required special techniques and precise planning. On behalf of the De Groene Boog consortium, Verboon Maasland contributed to the large-scale and specialized earthmoving work for more than 2.5 years.

Well before the start of the project, Verboon Maasland was approached by Van Oord, co-partner in the consortium, to help think about the excavation of the cofferdams. “Initially the deployment of wire cranes for the entire project was considered, but it soon became clear that this was not technically feasible,” says Sjors Kouwenhoven, foreman at Verboon Maasland. “The wire cranes would put too much pressure on the sheet piles and, in addition, in many situations the available space was tighter than previously estimated. Eventually the ‘specials’ around De Rotte were still excavated with draglines, but for the most part hydraulic cranes from pontoons were chosen.”

Squeeze or suck

With a total of 34 construction pits, the challenge was considerable: each pit had its own specific requirements and approach. “Especially the pits around De Rotte were complex, with many outriggers and limited working space,” Kouwenhoven looks back. “Here the soil was not pinched but carefully sprayed away and vacuumed to prevent damage to piles and soil. In all the other tubs we used this technique only around the piles, the vast majority was excavated ‘traditionally’ with a pincer in the wet.” The deployment of equipment varied greatly, with peak times when three wire cranes and two crawler cranes from Verboon Maasland were deployed simultaneously. “In addition, we had to hire quite a bit of equipment because we were also working on the A24 Blankenburg connection in parallel with this project.”

Apart from the technical challenge, Kouwenhoven says the planning was also quite challenging. “There was a lot of diving work involved, which ran out quite often while deadlines were not pushed back. It was up to us to respond to this flexibly, and we were well entrusted to do so.” Verboon Maasland and Van Oord shared equipment and work, which resulted in a pleasant collaboration and led to continued contacts and follow-up orders even after the project was completed. “We also gained valuable experience here, which will also come in handy on other projects.”