Slurry lagoon lining in Somerset

Stores on wet ground

On the Levels and the clay vales the water table is high for much of the year. A lagoon there has to keep its contents in and, if it is dug below groundwater, cope with water pressing up under the liner when the store is emptied. Your designer deals with that through the formation and any underdrainage, and our lining follows the design.

Soft clay and peat also make the formation harder to get right. The banks and base must be firm and properly profiled before we start, and we check that rather than build on a soft surface.

Single, double and covered

The permit and your consultant set the build-up. A modest store may need nothing more than a 300gsm fleece beneath a single welded sheet of HDPE or LLDPE. A larger or higher-risk store may call for two welded sheets with a drainage medium between them, so seepage through the top sheet is collected and shows up at an inspection point. Where specified, a floating cover keeps rain off the slurry, which matters in a wet western county where open stores fill with rainwater as well as slurry.

Who does what

Existing earth-banked lagoons can often be relined after inspection, once the banks are re-profiled. It is usually cheaper than a new store and keeps the store in the place the farm is already built around.

• The earthworks are yours: base, banks and anchor trenches are cut by your contractor, and we don't dig
• Before delivery we compare the finished profile and trenches with the lining drawings
• Fleece, liners and any drainage layer laid and welded panel to panel
• Inlet pipes, the draw-off point and the level marker sealed through the liner
• A test weld carried out and recorded on every job

Access on the moors

Many Levels farms are reached along droves and narrow raised roads. Rolls of liner and fleece are heavy, and a soft drove in February will not carry a delivery lorry. We plan lining work for the drier part of the year where we can, check the route with you before we book transport, and keep the number of vehicle trips down by bringing fleece, membrane and welding kit together. Rolls are stored off the ground on site and kept covered until they are laid.

Records for inspection

AD plants supplying digestate to Somerset farms need the same discipline as the farms themselves. Every lagoon we line ends with a compliance QA pack: certificates for each roll of fleece and liner, our welding log, and drawings of the store as built. That is what the inspector and the insurer will ask for, and it stays with the farm.