Infiltrating rainwater: the triple challenge of Groessen

Rockflow project, 2021

How to infiltrate rainwater in the face of the triple challenge of a high water table, heavy showers and prolonged dry spells? The municipality of Groessen found a flexible, natural and durable solution in Rockflow.

This was the situation

In Groessen, just a stone's throw from Arnhem, a solution was being sought for collecting and infiltrating rainwater.
Groessen has a high water table. This means that solutions located deep down would be underwater for much of the year.
Underground, existing cables and pipes must be taken into account. A solution involving rainwater discharge requires existing cables and pipes to be relaid, otherwise the drainage pipe ends up deep underground, in the groundwater.

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Project details

Project location	Groessen, the Netherlands
Client	Municipality of Duiven
Partners	NTP Infra Zevenaar

The solution: stone wool

The team in Groessen found an infiltration solution that satisfies all the (special) requirements: stone wool. The existing rainwater discharge was replaced by Rockflow linear infiltration and drainage system beneath the road over a distance of 800 linear metres. Using Rockflow, rainwater is efficiently collected beneath the road. Because where the water falls, it is naturally infiltrated into the substrate.

This Rockflow buffer is made from a natural mineral material – stone wool. This material can very quickly absorb up to 95% of its volume in water before gradually infiltrating it into the substrate. This means that infiltration differs substantially from the original drainage pipe solution, where the water is transported. Rockflow results in less strain on the sewer system and helps to restore the natural water balance.

The project in Groessen is an extensive one. For one thing, the sewage drain is being replaced, then the Rockflow components are installed and rainwater discharges from the buildings and the sink water traps are connected to the buffer. The Rockflow system is installed at the same depth as the cables and pipes. Where these are ‘in the way’, Rockflow buffers are split and then connected together using pipes. So there is a connection and it functions as one system.