Slurry lagoon lining in Derbyshire

Why the rock makes lining matter

Carboniferous limestone is riddled with joints and solution channels. Rivers such as the Lathkill and the Manifold run partly underground in dry weather, which shows how freely water moves through it. An unlined or cracked earth store on that ground can lose effluent into the rock with little warning at the surface.

Further south, on the clays and gravels of the Dove valley around Ashbourne and Hilton, the risk shifts to the watercourses beside the fields. Either way, a welded liner over protection fleece removes the ground from the question.

The build-up your design calls for

Your consultant sets the capacity, freeboard and the liner build-up against the storage rules. We install what is specified, which on Derbyshire farms usually means one of three options.

• Fleece and a single welded HDPE or LLDPE liner for a straightforward slurry store
• A double-lined build with a drainage layer between the sheets, routing any seepage to a leak-detection point
• Either of the above with a floating cover, which also keeps rainfall out of the stored volume

Rain, and why covers earn their keep

The High Peak is one of the wettest corners of the county. Every drop that lands on an open lagoon has to be stored and spread with the slurry, so on an upland farm a floating cover can free up a useful share of the capacity. Whether one is fitted is for the design; where it is, we weld it to suit the lagoon's shape.

Giving an old store a new skin

Plenty of farms have an earth-banked lagoon built decades ago. If inspection shows it can be saved, your earthworks contractor reshapes the slopes and cuts the anchor trench; we walk both with the lining drawing in hand before any roll is delivered. Fresh fleece goes down, then the welded sheet, and it often costs less than starting a new store.

The filling pipe, the draw-off and any depth marker each get their own sealed boot through the liner. A trial weld is logged on the day, and the farm is left a file of product data sheets, weld logs and as-built drawings.

Peak farms sit at the end of narrow lanes between drystone walls. We ask early about turning space and gateway widths, so the rolls arrive on a vehicle that can reach the lagoon and the welding kit can be carried to the crest without damaging walls or verges.