Attenuation tank installer in Somerset

Why storage is the norm on the Levels

The Levels and Moors are low, flat ground of clay and peat, drained by the Parrett, Tone, Brue and Axe and a network of rhynes. The water table sits close to the surface for much of the year and large areas flood in wet winters. Percolation tests there rarely pass, and a soakaway in that ground would sit full of water.

Runoff is instead discharged to a watercourse or sewer at a controlled rate, set through the planning conditions and agreed with the Lead Local Flood Authority. The attenuation tank holds the storm while the flow control lets it out at that rate. Under the 2025 national SuDS standards that discharge is pushed towards greenfield rates, with allowances for climate change, so storage volumes on Levels sites are rarely getting smaller.

Keeping groundwater out

In Levels ground a tank has to resist water pressing in from outside as much as hold water inside. We heat-weld every membrane joint and log a test weld before any backfill goes on. Flotation is a design check for your engineer, who sets the depth with it in mind.

Wet ground also makes the formation harder to get right. The excavation has to be dewatered and the base firm and level before we lay fleece and membrane, and if it isn't, we'll say so and wait rather than build on a soft or flooded base.

How we work in Somerset

The system's design and sizing sit with your engineer, and the excavation, formwork and backfill with your groundworker; we don't dig. Once the base passes our check, we put down 300gsm fleece and the membrane, stack the crates until they reach the drawn volume at the specified loading class, join up the inlet, outlet and flow control, and leave you with the QA and handover file for building control. Choose supply and install or install only; crews come down from our Tamworth base.

Farm and AD sites

Somerset has a lot of agricultural and anaerobic digestion work, and those sites often need lining beyond the stormwater tank. We line slurry lagoons and containment bunds with the same welded-membrane approach. At an AD plant at Bognor Regis in West Sussex we lined the containment bund over protective fleece, dressed it up the walls and sealed every penetration, so a spill stays inside the bund.

On a farm or AD site the stormwater tank and the lining work are often on the same programme. Planning them together means one set of welding records and one handover pack for the whole package.