Mythical towers mark new entrance area Amersfoort

Castalia and Kalliope are part of the new urban district Hogekwartier on Hogeweg in Amersfoort. The new construction of the towers is a project of De Alliantie. The housing corporation selected TBI company Koopmans Bouwgroep for the development and construction. Nico van der Zee, deputy director, was responsible for the development process within Koopmans. He says, "Based on the budget and initial concept, we started the development of the plan in March 2018. We did this together with De Alliantie, Moke Architects, Aveco de Bondt, Installation company Van der Sluis and the municipality of Amersfoort. Together, we arrived at a design with an optimal price-quality ratio and a residential program that makes maximum use of the available usable floor space."

Landmark

Of the two residential towers, Castalia is the tallest, with 20 residential floors and 101 owner-occupied and rental apartments. Kalliope has ten residential floors with a total of 64 social rental apartments. Underneath the towers is a communal parking garage. "Both buildings have a high-quality, fresh look," says Van der Zee. "With their four-story plinth and clear structure, they manifest themselves as landmarks in the city's new entrance area. At the same time, the all-sided facades and staggered balconies create a transparent and dynamic facade image. Furthermore, the interaction with the surroundings has been carefully considered. The greenery of the neighboring Valleikanaal extends into the courtyard garden and from the apartments you have a beautiful view of the city center or the outdoor area."

Cover

During the design process, the government decision came that all new projects had to be gasless. A collective WKO system was chosen for this project. "Quite a change," said Van der Zee. "And especially with the knowledge that we had to start construction within a year of starting this development. All parties involved, including certainly also the municipality of Amersfoort, worked hard to achieve this objective. With success." 

Traditional parking garage, tunneled towers

In early 2019, Koopmans Bouwgroep started the construction of the sunken parking garage. This was largely constructed traditionally on site. Above the parking garage, the residential towers were constructed using the tunnel casting method. Van der Zee: "We created a clear building structure in which we could accommodate a variable residential program per floor. The high tower has four or five homes per layer. The low tower has six on each layer. Both based on the same footprint." Koopmans Bouwgroep included the balconies and installations directly in the shell construction phase. 

Integral collaboration

"The expression 'A good start is half the battle' certainly applies to this work," said Van der Zee. "The low tower has been completed on schedule and the construction of the high tower, which is expected to be completed in June, is progressing well. This is largely due to the thorough preparation. Integral cooperation has been central from the beginning. As a team, we defend each other's interests. We agree among ourselves who does what and we coordinate the work seamlessly. The environment has also been involved from the planning phase. These efforts are not for nothing. They contribute to making the plans a success in a pleasant way. And that is reflected in the end result. When I drive into Amersfoort from the A28 and see the towers looming, I am enormously proud of the result of a successful collaboration."