Stormbloc® Optimum is a robust geocellular storage system that provides underground storage and infiltration of urban runoff as part of a sustainable drainage system (SuDS). A 96% storage coefficient means that it can store 960 litres of attenuation volume per cubic metre, and its lightweight plastic materials and sturdy design make it easy to transport, quick to install and extremely durable, even beneath high-traffic urban areas such as roads, car parks and warehouse yards.

Stormbloc® Optimum stacks into compact nests during transportation and storage, providing huge space and cost savings during delivery and on site. When stacked, Stormbloc® Optimum boxes occupy 75% less volume, freeing up valuable space on site and meaning that a single lorry can deliver pallets of boxes equivalent to almost 350 m3 of storage—cutting the number of delivery vehicles required.

Stormbloc® Optimum is modular and easily customisable, giving engineers the freedom to configure storage for even the most challenging SuDS project.

We have introduced a new Stormbloc® Optimum Inspect chamber with the option of a sand trap to effectively manage sediment levels and help designers and planners meet regulations.

Stormbloc® Optimum is only available in the UK and Ireland


Designed for

High storage


Store and infiltrate more water, even in challenging sites

Combining strength with a storage coefficient of 96%, Stormbloc® Optimum is a highly effective underground water retention and attenuation system, enabling engineers to plan and design effective SuDS systems even in difficult urban environments with high traffic levels.

Stormbloc® Optimum can withstand heavy goods vehicle traffic with an overall load of up to 60 tons, and can be installed at base depths of up to four metres. An optional "offset stacking" configuration--like brickwork--increases the strength of the system where required. 

Each Stormbloc® Optimum box also incorporates two parallel inspection and maintenance tunnels, to ensure effective ongoing operation.

Customise your storage

As Stormbloc® Optimum is a modular geocellular block system it can be configured in multiple ways to meet site-specific storage requirements, making it far more flexible than a conventional stormwater attenuation or retention tank.

Length, width and depth of storage can be customised in order to meet even the most demanding of drainage environments, including deep residential, commercial and industrial applications subject to heavy traffic loadings, such as roads, motorways and car parks. Two inspection channels enable easy inspection and maintenance. 

Save space on site and during transport

Stormbloc® Optimum stacks into compact nests for transportation and storage—reducing the volume to just 30% of the final installed product—saving valuable space both during delivery and on site, and making handling quick, easy and safe. The units unstack simply for installation.

With up to 75% space reduction, a double pallet of stacked, nested boxes delivers more than 14 m3 of stormwater storage, and a single lorry delivery can provide 345 m3—saving you money.

Save time during installation

On a construction site time is a valuable commodity, so Stormbloc® Optimum is designed with handling and installation in mind—helping you to cut the costs of installation. Once delivered, installation is quick and easy—the lightweight components fit together simply by hand to create the modular, stackable storage boxes that can be arranged to the desired configuration.

Integrated self-centring clip-on lugs and simple optional masonry connections make manual installation quick and straightforward.

How it works

How it works

The modular blocks are installed and connected together on site in the desired configuration, using self-centring clip-on lugs and simple optional masonry connections. 

The modular nature allows the system to be connected to multiple inlet and outlet pipes. 

Each box incorporates two parallel inspection and maintenance tunnels to allow access by CCTV camera and high-pressure flushing system. 

Technical information

Technical information

Storage performance

Storage coefficient: 96% (960 l per m3)

Storage capacity, full block: 0.405 m3

Storage capacity, half block: 0.221 m3


Material: 100% polypropylene

Maximum load: 60 tons


Full Box

LWH: 800 x 800 x 660 (mm) - 0.422 m3

Half Box

LWH: 800 x 800 x 360 (mm) - 0.230 m3

Delivery & Installation

Units per pallet: 34

Maximum Installation depth: 4 m


Unit weight: <10 kg per box



Case Studies

Case Studies