Slurry lagoon lining in Hampshire

Livestock over an aquifer

The downs are mostly arable, but Hampshire still has dairy herds in the river valleys and on the clay towards the Solent and the Surrey border, outdoor and indoor pig units on the chalk, and a growing number of anaerobic digestion plants producing digestate. All of them need somewhere to hold liquid manure or digestate until it can go on the land.

On fissured chalk, a store that seeps can reach groundwater and chalk streams like the Test, the Itchen and the Meon. That is why an earth-banked lagoon here is increasingly lined, and why inspectors look closely at how it was built.

Single liner or double with leak detection

Your consultant and the permit set the build-up, and the stored material drives it. A modest dirty-water pond on the farm might get no more than fleece and a single welded sheet. Digestate, or a store over sensitive chalk, can justify two sheets separated by a drainage medium; liquid that gets past the upper sheet then collects where the farm can check for it, rather than vanishing into the ground.

A floating cover can go over the top to keep rainwater out, which saves storage capacity through a wet winter, and to cut odour near houses. We install whichever build-up is specified.

• Protection fleece over the formed banks and base
• Secondary liner, welded panel to panel
• Drainage layer to a leak-detection point, where specified
• Welded primary liner
• Floating cover, fill points, draw-off and level gauge

Who does what

Banks, floor and anchor trenches are shaped by your earthworks firm. Before any material is delivered we measure those against the lining drawings, then lay, weld, detail and test. Every Hampshire lagoon has its test weld logged, and the compliance file holds material certificates, weld logs and as-builts for a SSAFO inspection or your insurer.

We also line existing earth lagoons once they are emptied and the banks re-profiled, which is often cheaper than building new storage.

Containment work in the region

Along the coast in West Sussex, an anaerobic digestion plant at Bognor Regis had its containment bund lined by our crew. Every seam there was extrusion welded, and each corner, the transition up the bund wall and every pipe through it were formed and sealed by hand. A digestate lagoon in Hampshire gets the same attention at its fill points, draw-off and anchor trench.

Containment of this kind is judged on the day something goes wrong, years after the crew has left. That is why the weld record and the as-built drawings matter as much as the liner: they let an operator show a regulator or an insurer exactly what was built and how it was tested.