Attenuation tank installer in Liverpool

Attenuation on Liverpool's brownfield land

A lot of Liverpool's new building goes onto land with a past: former docks and warehouses in the Baltic Triangle and north Liverpool, old industrial plots around Speke and Kirkby, cleared streets in Anfield and Everton. The old drains come out, and the new surface water system usually has to hold water back before it reaches the sewer or the Mersey. Where there's no room for a pond, a geocellular tank under the yard or car park does that job.

Much of the city sits on low-lying ground beside the estuary. A lined tank there has to be watertight in both directions, keeping storm water in and groundwater out, or it won't give the storage it was designed for. Brownfield formations also tend to throw up old brick, concrete and pipe, so we look at the base before any fleece goes down and ask for anything sharp to be cleared.

Working on live industrial sites

At Knowsley we lined an attenuation tank on an operational industrial site: protective fleece and a welded impermeable membrane, detailed around the structures on site and tested at the seams, while the site kept working. That's typical of the estates and distribution parks around Liverpool, where a tank goes in beside running plant, live traffic routes and existing drainage.

On sites like that we agree the working area, access and delivery times with the site team before we arrive, keep our welding kit inside the area we've been given, and leave the tank sealed and documented so the excavation can be closed without waiting on us.

Who does what on a Liverpool tank

You can buy the materials through us or have us fit crates and membrane you've sourced yourself. Each seam is fused with heat rather than taped, and the crates run at a 95–97% void ratio, so the footprint stays as small as the storage allows.

• Drainage engineer: designs the tank, sizes it and fixes the outflow rate.
• Groundworker: excavates, forms the base and backfills. We don't dig.
• Aquatech: fleece, membrane, crates, connections, welding and testing.
• You: a QA and handover pack with the recorded test weld, as-built details and sign-off.

The rules the design answers to

Drainage conditions across the city region rest on the NPPF, Approved Document H and the 2010 Flood and Water Management Act, and the 2025 national SuDS standards now set the expectations on major schemes. The council, as lead local flood authority, reviews the drainage strategy at planning. We don't take the design on; we build what your engineer got approved and give you the records to show it was built properly.