Slurry lagoon lining near the Black Country

Farming at the edge of the conurbation

Walsall's green belt around Aldridge and Stonnall, the countryside south of Stourbridge, and the South Staffordshire farms beyond Wolverhampton are all a short drive from the towns. Dairy and beef units, livery yards and mixed farms work that land, and an older earth-banked store there is often a candidate for lining rather than replacement.

Being close to towns raises the stakes. A leak reaches a brook or a canal feeder quickly, and neighbours notice the smell. A welded liner and, where specified, a floating cover deal with both.

Saving an existing store

Plenty of farmers ask whether an old lagoon can be brought back into use. Often it can, after an inspection. The farm's own earthworks firm reshapes the banks and cuts the anchor trench; we then walk both against our lining drawing, so any correction happens before rolls of membrane are sitting on the yard.

Next comes a cushion of fleece over the reshaped store, and the liner is welded across it a panel at a time, with the fill pipe and draw-off sealed in as we reach them. A trial weld is peeled and logged before seaming starts.

Single, double or covered

The build-up depends on what's stored and what the permit requires.

• Single liner on fleece for many slurry and dirty-water stores
• Double liner with a drainage layer between, for leak detection
• HDPE or LLDPE, chosen for the contents and the site
• Floating cover to cut rainwater volume and odour

Weather, access and a farm that keeps working

A lagoon can't be lined in driving rain or high wind, and farms on the exposed ground towards Kinver and Codsall get plenty of both. We watch the forecast with you and come at short notice from Tamworth when a dry spell opens, rather than committing to a date and fighting the weather.

The farm carries on around us. Milking, feeding and muck spreading don't stop, so we agree where our van, rolls and welders sit, which gates stay shut, and how tractors get past while the store is out of use.

Nearby work and handover

Our closest comparable job is east of here at Bodymoor Heath in the Tame valley, where 2,000m² of LLDPE was welded on site and sandwiched between protection fleece, and the team worked through wet weather to finish on programme.

At the end, the farm gets a QA folder listing the products laid, every seam test and the finished layout of the store. Inspectors and insurers tend to ask for exactly that.