New rainwater system will reduce overflows and increase water quality

Following an increase in extreme weather, more urban areas suffer from old systems not suited to handle the large amounts of water that awaits. As a result, the number of overflows from sewers and streams is increasing as well, damaging nature, infrastructure, and private properties. Therefore, municipalities and utilities are looking towards sustainable solutions fitted for our current and future climate.

Novafos, HOFOR, Gladsaxe Municipality and Herlev Municipality have initiated Kagsåparken Rainwater Project with the ambition to transform Kagsåparken to meet the demands of future rainwater management. Currently, the stream in Kagsåparken often overflows during heavy rain because the underlying drainage system cannot handle the amount of water passing through. When the drainage system overflows into the stream, the water quality of the stream is affected negatively, and the stream overflows with a combination of wastewater and rainwater into the surrounding area.

To relieve the drainage system and reduce the number of overflows, the park and stream will thus be rebuilt into a large rainwater system. The project is part of the big Harrestrup Å-programme that aims to revise and transform several streams in the area.

The complexity of the project means that Ramboll will be collaborating across internal divisions, as well as partnering up with Gottlieb Paludan, and Klimakom .

The project design includes:

• 80.000 m3 of lower-levelled areas that will serve as detention ponds.
• A new pipe with a 3000 m3 volume that will retain up rain and wastewater until the drainage system can handle it.
• A slinged catchment area and infiltration basins that will collect and cleanse the rainwater before it is led out into the stream.

With the new rainwater system, the current number of overflows will be reduced from more than 50 to an average of 10 a year, as it will become easier to control and steer large amounts of rainwater in the right direction. Despite the big restructuring, the park will keep its natural look and still function as a recreational space for residents of the area. Ramboll’s design will improve the condition of the surrounding environment and reduce damage costs, thereby increasing liveability for locals.