Revolutionary water storage system at Lorentz in Leiden

Developing builders Hurks bouw & vastgoedontwikkeling and Van Wijnen, the municipality of Leiden and investor Syntrus Achmea Real Estate & Finance are implementing a revolutionary water storage system in Lorentz. Lorentz is the first new construction project in the redevelopment of the Leiden Station area. On one of the tower roofs a substantial water buffer is realized via retention crates. The outlet of the buffer is equipped with a Smart Flow Control, or a "smart meter. This water buffer is used, among other things, to feed the sprinkler system of the lower green roof. It is the first time this combination has been applied in the Netherlands.

Water storage with Smart Flow Control combined with sprinkler system
Stefan de Ruijter, project director on behalf of the collaboration between Hurks and Van Wijnen: "The implementation of Lorentz is in full swing. Even in this phase of the project, we have an eye for innovations, developments and current affairs. Due to climate change, rain showers are becoming increasingly heavy. We examined with the project team to what extent it was still possible to add water storage capacity in Lorentz during construction. "

He continues: "On one tower roof, a Smart Flow Control regulates the water level in the retention crates and uses current precipitation data to recognize when a shower is coming. The system then regulates the water flow itself. When it is dry, the system holds the water. If a new downpour is detected, the system automatically empties, restoring maximum storage capacity. The captured water is also used to water the plants on the lower roof of the plinth building. This saves pure drinking water. On the lower green roof, water-retarding and partially water-storing sheets are also used."

Most Sustainable Kilometer of the Netherlands
The project team was inspired in part by their contribution to the 'Most Sustainable Kilometer in the Netherlands' initiative. In it, companies, governments, citizens and knowledge institutions work together to transform the station area into the most sustainable inner-city piece of the Netherlands by 2025. Meanwhile, 29 organizations have joined this community and signed the Green Deal. One of the themes the community is working on is "dry feet. Indeed, the densification of the area around Leiden Central Station requires a careful plan for water collection.

The municipality of Leiden is delighted. Alderman Fleur Spijker (Sustainable Urbanization): "This innovative water storage system reduces the burden on the sewerage system and saves pure drinking water. In Leiden we want to solve several social issues simultaneously with building projects. So in addition to building residential and office space, we are also tackling social and sustainability issues. We cannot do this alone. Great that all the developing parties were so enthusiastic that even during the construction process this water storage system was added to the building. I hope this result is an inspiration for all upcoming construction projects in the Station Area."

Collaborative partners
Close cooperation between Hurks, Van Wijnen, the municipality of Leiden and Syntrus Achmea led to the development of Lorentz. Partly because of this good cooperation, it was possible to implement sustainable optimizations even during the realization phase, such as making the mixed-use building completely gas-free and choosing an innovative water storage system. "Sustainability is a very important issue, both for our clients and for us," says Nicole Maarsen, Director of Real Estate at Syntrus Achmea. "These optimizations are good for investors and tenants, and they reduce the building's impact on the environment."

Subcontractor for the construction of the retention roof was Royal Ginkel Group in collaboration with Optigroen. Advisor on behalf of the municipality was Polderdak.