Slurry lagoon lining on New Forest farms

Where lagoons are needed

Housed dairy herds produce the slurry, and those herds sit mostly on the farmland fringing the Forest: in the Avon valley around Fordingbridge and Ringwood, towards the Test near Romsey and Totton, and on holdings north of the A31. Commoning holdings are usually small and many keep stock outside, so few of them need a lined store.

When a farm in this area does build or upgrade a lagoon, the stakes are high. The Hampshire Avon and the Forest's own streams flow through protected habitat to the coast, and a store on sand or gravel that seeps will reach groundwater quickly.

The lining build-up

Your consultant sets the capacity, freeboard and build-up to suit the farm and the regulations, with SSAFO applying to any store that is new or substantially changed. We install what is specified. That could be fleece with a single welded sheet on top, or an upper and lower sheet parted by a drainage layer, piped to a sump that shows whether the top sheet is leaking.

Where rainfall onto an open lagoon eats into storage over the winter, a floating cover keeps the rain out and cuts odour, which matters on farms close to villages and holiday lets.

On the farm

The farm's earthmover shapes the banks, floor and anchor trenches, and we measure them against the drawings before the liner is sent. Fleece is laid as the bottom layer, the sheet is welded together on top of it, and a sample weld is tested and written up. Inlets, the draw-off pipe and the level gauge are sealed through the liner, with a cover added where the design includes one.

We also reline existing earth stores once they are emptied and re-profiled. You get the compliance pack: materials, weld records and as-builts for the inspector and insurer.

• Profile and anchor trench check before delivery
• 300gsm fleece beneath the liner
• HDPE or LLDPE, single or double
• Recorded test weld and full QA pack