Soakaways & Attenuation Systems

Surface water problems don't just cause puddles. They can create slip hazards, damage building fabric, overwhelm drainage networks, and trigger repeated flooding around entrances, car parks, loading bays, and landscaped areas.

ICE Drainage installs and repairs soakaways and attenuation systems across London and the Home Counties, supporting commercial property teams, hospitality sites, and facilities management with practical, compliant surface water solutions.

What is a soakaway?

A soakaway is an underground system that collects surface water and lets it soak into the ground. Soakaways are commonly used where there's no suitable surface water connection, where you need to reduce runoff and pooling, and where the ground conditions allow infiltration.

Soakaways can be built using different methods, such as modular crate systems or traditional aggregate-filled pits, but the principle is the same: store water temporarily and disperse it safely.

What is an attenuation system?

An attenuation system stores surface water and releases it at a controlled rate. This helps prevent flooding further downstream and reduces pressure on drainage networks.

Attenuation is commonly used when infiltration isn't suitable due to poor ground conditions, when discharge needs to be restricted to a set flow rate, when you're managing larger catchments such as car parks, roofs, or yards, or when a site needs to meet planning or drainage strategy requirements.

Attenuation solutions can include tanks, oversized pipe runs, or other storage structures, usually paired with a flow control device.

When you might need a soakaway or attenuation system

These systems are often needed when you're experiencing standing water in car parks, service yards, or loading bays, regular pooling near entrances and walkways, flooding after heavy rainfall, overloaded gullies or surface water drains, runoff issues from roofs or hardstanding, or drainage problems linked to site changes or refurbishments.

If the issue keeps coming back, it's usually a sign the existing surface water drainage is undersized, blocked, incorrectly graded, or not designed for current rainfall patterns and site use.

Commercial applications

We commonly support hotels and leisure sites with large roof areas and car parks, restaurants and pubs with external areas that need to stay safe and usable, facilities management teams responsible for multi-site maintenance, commercial buildings with recurring surface water complaints, and schools and public buildings with waterlogged grounds and hardstanding.

The goal is to keep your site safe, operational, and protected from avoidable water damage.

Our approach: assess, design, install

Surface water systems need to be designed properly, not guessed at.

1) Site assessment

We review where water is collecting and where it's coming from, the ground levels and falls, the existing gullies, channels, and pipework, the soil type and infiltration potential for soakaways, and any constraints such as utilities, access, or trading hours.

2) Recommendation: soakaway versus attenuation

We recommend the most suitable option based on what's achievable and maintainable on your site. If infiltration is viable, a soakaway may be the simplest solution. If it isn't, an attenuation system with controlled discharge may be needed instead.

3) Installation and reinstatement

We install with long-term performance in mind, using correct excavation and base preparation, a suitable geotextile or membrane where required, correct connections from gullies, channels, or pipework, sensible access for inspection and maintenance, and practical reinstatement of surfaces where agreed.

Repairs and upgrades to existing systems

Not every site needs a full replacement. We can help with soakaways that have failed and no longer infiltrate due to silt, collapsed or damaged pipework feeding the system, poorly designed systems causing water to back up, and upgrades where site changes have increased runoff. If a system keeps failing, we'll explain why and propose a realistic fix.

Keeping it working

Soakaways and attenuation systems can fail if they aren't protected from silt and debris. We often recommend silt traps or catch pits upstream, accessible inspection points, regular gully and channel drain cleaning, and clear handover guidance for your FM or site team. This helps protect the asset and avoid expensive failures.

Minimising disruption on live commercial sites

Most sites can't afford downtime. We can plan work around trading hours for hospitality sites, access windows and permits on FM-managed sites, quiet periods and shutdowns, and safe segregation and site rules. If out-of-hours work is needed, we'll advise on what's practical.