Slurry lagoon lining in Northamptonshire

Livestock in the west, digestate everywhere

Eastern Northamptonshire is mostly arable, with few herds and little slurry to store. The rolling country to the west is different. The Nene, the Cherwell and the Leam all rise on the high ground near Daventry, and the farms in those headwaters are where herds, and their slurry stores, are more common.

Digestate is the other source of work. Crop- and manure-fed AD plants produce a liquid that has to be held until it can be spread, and it needs the same contained storage as slurry.

Protecting the headwaters

A leaking store on high ground can reach the start of a river system that runs right across the county. The Nene alone flows from here through Northampton, Wellingborough and Oundle on its way to the Wash. Storage rules, SSAFO among them where a store is new or substantially altered, expect capacity, freeboard and construction that will not leak. Your consultant confirms what applies; we build the lining to meet it and document every weld.

Build-ups we install

How many layers a Northamptonshire store needs comes down to its contents and to the conditions set by the regulator or the farm's insurer. The options run from simple to heavily protected:

• A single welded HDPE or LLDPE liner on a 300gsm protection fleece
• Two liners with a drainage net between them, draining to a sump you can dip
• A floating cover over the top to keep rain out and odour in
• Pipe entries for filling and emptying, and a depth gauge, sealed into the sheet

On the farm

Banks, floor and the anchor trench are shaped by the farm's earthworks contractor before we arrive. We walk them with the lining drawing in hand, and on the stony brash of the uplands we look hard for anything that could push through the fleece. Liner panels are welded together on site, and on a double-lined store the primary liner is welded over the drainage layer once the secondary is complete.

A trial weld is cut and tested on every lagoon before the panels are joined. The QA pack lists materials, weld results and as-built details for the inspector and your insurer.