Client : A London borough
Contractor : RPM Services
Project size / Area sq ft : 280m of rain gardens
Completion date : Summer 2024
Products used : Netafim smart irrigation system, Meristem Design rain gardens and Wavin AquaCell Core R

Project overview
Wavin worked in partnership with Meristem Design to create a smart rain garden in a Central London borough which allowed for both greenification and irrigation. By working with Netafim, another Orbia business, they were able to use smart technology to monitor moisture levels in the soil and recycle captured and stored rainwater to water the plants in times of drought. This will provide vast savings across the lifetime of the project.

The challenges
Following consultation with the local community, a London borough sought to refurbish a 0.5km stretch of road, greenifying the entirety of one side of the carriageway.

This would be delivered with the use of rain gardens totaling nearly 400m in length. While this proposal would deliver excellent results with respect to SuDS guidance, one concern was the cost of maintaining such a large asset, especially in an ever-warming and dry London. The borough had installed similar, smaller rain gardens previously to great success. However, a common pain with earlier installations, and a growing concern for this new site, was the cost of watering the proposed green infrastructure during extended dry periods.

The solution
Following site visits and conversation between all stakeholders, a ‘smart rain garden’ solution was developed. Pairing Wavin’s water management expertise with Meristem Design’s rain garden installation, the client now has an underground rainwater storage tank volume capable of providing approximately 5 weeks’ worth of irrigation for use during dry periods. Using sub-surface moisture sensors and irrigation lines, the solution only draws on the retained rainwater when it is needed. Furthermore, the storage system is filled using treated surface water runoff that infiltrates through the rain garden into a perforated pipe.

Why use Wavin's system?
One ongoing concern for customers with shallow SuDS systems such as rain gardens is their need for regular maintenance. By using infiltrated and retained rainwater, paired with a smart irrigation system, installations such as the one in London can draw on the value of free rainwater that falls on the site instead of paying for it. The result is a reduced OPEX cost which outweighs the initial CAPEX investment in the space of a few years. Furthermore, grey elements complement the green, ensuring they remain as designed.

In wetter periods, the ‘smart’ system includes an active drain down function. In turn, this will relieve pressure on the local surface water sewer and provide partial storage capacity with the rain gardens, to mitigate against low volume flood events. This is achieved by integrating predictive algorithms linked to weather data.