Platform on new construction, renovation, restoration and transformation
The reason is clear: AkzoNobel and Stibbe, the former main tenants of two identical office towers on the north side of Amsterdam Zuid station left for new construction sites in 2016. The impending construction of the Zuidasdok gave owner Commerz Real cause for urgent redevelopment. With Provast as delegated developer, it was decided to undertake a substantial upgrade, in the form of a hotel tower and an office tower connected into one ensemble. A technically complex operation, for which J.P. van Eesteren provided the best solutions.
Sheet piles form the building pad for the parking levels under the east tower.
"In 2013, when we started planning, the market was poor but the location was still exceptionally good," says Provast project director Jurjen Thomas. "At Provast's direction, the owner chose to transform one tower into a hotel and enlarge the other into modern offices. This will house the Spanish hotel chain Meliã with its first Dutch branch. The western tower of 64 meters in height will be topped with three floors, including a skybar - the first on the Zuidas. The office tower will be expanded from 14,000 to about 23,000 m² GFA. That space will be found precisely in the width: because of the need for large floor areas, a new low-rise section will surround the tower, equipped with an atrium. Both existing buildings will be finished with a new element façade and forged into an ensemble by a framing of the inner garden. On the face of it, good construction was possible, but there were many underlying requirements and environmental factors."
Complex construction pit
First, the desire of owner and architect to create a single ensemble. The decision to build the Zuidasdok, widening the infrastructure bundle through the Zuidas, necessitated demolition of the parking garage, for which new facilities had to be found. "That proved no mean feat," says Thomas. "For the three new parking levels under the towers, a complex building pit had to be created. Grout anchors from the adjacent WTC turned out to be present in the work area, and the street level of the adjacent Strawinskylaan is higher than ground level. Moreover, the number of professional stakeholders is considerable: the municipality, the central government, as well as the owners of the WTC and office building Atrium. The issue was to select a contractor who is good at technical complexity and high-quality collaboration. Also because there is planning pressure on the project because of the Zuidasdok."
Sound solutions
A proactive role by Provast on behalf of the owner in the preliminary process led to an Engineer & Build agreement with J.P. van Eesteren after the DO was developed. "They offered the most thorough solutions to the technical complexity and offered optimizations," Thomas said. "And J.P. van Eesteren has a good track record in environmental management."
The west tower's topping will include a sky bar.
"The complexity is mainly in the construction pit and environmental factors," explains project manager Paul van Kats of J.P. van Eesteren. "Due to the lack of a natural water-retaining layer, soil injections were chosen, following the insertion of sheet pile walls and bored piles for the construction of the parking garage. Then the construction pit will be excavated. To keep the east tower stable, it is provided with a strut frame against the permanent sheet pile walls. After that, the floors will be poured." Construction will also start soon on the Zuidasdok, where the A10 will be brought underground. "The tunnel trench will pass just a few meters from 'our' facades. Cooperation with stakeholders, the layout of the construction area and monitoring will continue to require attention until completion."
Sustainability
In total, the layout of the construction site and related logistics must be changed seven times. Van Kats: "We have found co-makers who can fully participate in the planning and logistics, such as De Groot and Visser, Unica and Voorbij." The new facade of the hotel tower will be wind and watertight this spring; completion of the ensemble is scheduled for 2021. "For a transformation into a hotel, challenging because of the built-in package, we can operate relatively efficiently, including early storage on the floors." The office tower will receive a BREEAM 'Excellent' certificate (including WKO combined with district heating; solar panels), the hotel a GPR score of at least 8. "Because of the complex environment and combination of functions, this is a unique project," Thomas says in conclusion. "With the development of a new Amsterdam Zuid station comes a second passage connecting north and south, bringing 2Amsterdam even more into the center of the Zuidas. The new entrances have been given their orientation to the south, connecting better with this central location. This makes 2Amsterdam the ultimate redevelopment, in which all forms of cooperation come into their own."
