Underground Stormwater Management
Manage surface water runoff with high-performance buried attenuation and infiltration structures.
The Nidaplast EP, AZbox and OPTIBOX systems enable the construction of buried stormwater attenuation and infiltration basins for sustainable surface water management. These lightweight yet structurally robust storage modules temporarily retain rainwater and storm runoff, then return it progressively to the ground or the drainage network. Fully concealed below ground, they free the surface for other uses — roads, car parks, green spaces — while reducing flood risk. A reliable, long-term solution for local authorities, consulting engineers and civil drainage contractors.
Our buried stormwater systems
Optibox
The Optibox system, with a 95% void ratio, represents a new generation of SAUL units with three-dimensional diffusion. It provides temporary stormwater storage and enables the construction of underground public or private structures that can be inspected and easily hydro-cleaned.
AZbox
The AZbox system, with a 95% void ratio, ensures the temporary storage of rainwater and allows for the creation of public or private underground structures that are controllable and hydro-cleanable.
Nidaplast EP
The underground rainwater storage modules nidaplast EP and nidaflow EP are polypropylene honeycomb blocks belonging to the SAUL family (Ultra-Light Honeycomb Structures).
Product range comparison
Type
Structure
Water distribution
Inspection
Compressive strength
Nidaplast EP
Rigid PP honeycomb blocks
External diffuser
Via drain channel
400 - 500 - 600 kPa
AZbox
Modular cassettes, clip assembly
Three-dimensional internal flow
Facilitated via inspection corridors
>300 kPa
Optibox
Modular cassettes, integrated self-locking connectors
Three-dimensional internal flow
Integrated inspectability
>300 kPa
Related case studies
See all our case studies
Key benefits
Below-ground storage
Frees the surface above for roads, car parks or landscaping while managing stormwater at source.
Flood risk mitigation
Attenuates or infiltrates rainfall and storm runoff to reduce the risk of surcharging drainage networks.
Full modularity
Systems adaptable to any site configuration, project footprint or storage volume requirement.
Frequently asked questions
What is the difference between an infiltration basin and a sealed attenuation tank?
An infiltration basin allows water to percolate progressively into the subsoil, supporting natural groundwater recharge. A sealed tank, lined with a geomembrane, stores rainwater for later reuse — typically requiring a submersible pump. Both approaches regulate stormwater flows and help prevent localised flooding.
Why choose a buried system over an open-air basin?
Underground storage offers a significant land-use advantage: the surface above remains fully available for other purposes — car parks, roads, public open space. Nidaplast buried systems also provide better landscape integration and improved safety, with no visible area of standing water.
Are Nidaplast structures suitable for trafficked areas?
Yes. EP, AZbox and OPTIBOX modules can all be installed beneath trafficked roads or car parks. Their high-strength geocellular design is capable of bearing significant imposed loads while ensuring the long-term structural integrity of the basin.
Do these systems require specific maintenance?
The basins simply need to be fitted with a pre-filtration device upstream to limit sediment accumulation. An access manhole must be provided for periodic inspection and maintenance, in accordance with the design engineer’s specifications.
Become a distributor
Distribute Nidaplast stormwater management solutions — recognised for their reliability, modularity and site performance.
Our EP, AZbox and OPTIBOX ranges are manufactured in France and supplied with dedicated technical support for hydraulic engineering projects. Our in-house design office provides layout drawings and technical sizing from consulting engineer or client specifications. We offer personalised commercial support to facilitate your product listing. Offer your clients buried attenuation and infiltration systems that comply with sustainable drainage standards (SuDS), planning requirements and the Water Framework Directive.
Proven technical solutions
Our products are developed to meet real site requirements: hydraulic performance, structural reliability and long service life are built into every system.
Committed to a reduced environmental footprint
At Nidaplast, we design recyclable products incorporating recycled materials, produced through a controlled manufacturing process with a low carbon footprint.
Dedicated technical support
Whether you need a technical specialist, design office input or commercial guidance, our teams support professionals at every stage of their project — in France and internationally.
