Repairs Underway at Troston Pig Slurry Lagoon

Stirling Maynard is currently involved in the design of an essential repair scheme for Troston Farms Ltd, after an agitator malfunction resulted in critical damage to its Suffolk-based pig slurry lagoon.

The lagoon sustained serious harm to its geomembrane lining system, and was emptied earlier in 2016 to facilitate the necessary repairs. This process revealed that the 1mm thick liner had split, with slurry present between the liner and the geotextile.

Anecdotal evidence suggests that the 5000m³ lagoon was originally constructed by Anglian Water, and later repurposed as a pig slurry lagoon as part of Troston Farms Ltd’s activities. The build up of sludge below the liner — observed during the emptying process — was evidence that improvements needed to be made to the lagoon’s original design for the farming company to continue using the facility to store slurry.

Troston Farms Ltd notified the Environment Agency, who provided guidance on the investigation and laboratory permeability testing required to investigate the issue. Stirling Maynard were then appointed to organise the task; designing a shallow testing regime to investigate an assumed 1m thick placed clay lining beneath the surface of the geotextile, thought to be present due to the permeable nature of the area’s natural sub-soils.

Whilst the results of the laboratory test demonstrated acceptable values of permeability in most of the shallow sampled material, not all of the samples complied with the standards set by the Environment Agency. Our team’s investigation demonstrated that the assumed placed clay lining was not present, and although a substantial quantity of clay was discovered, it had been combined with other made ground.

Through discussions between Troston Farms Ltd and the Environment Agency, an agreement was reached to repair the lagoon using a replacement 1.5mm thick single HDPE lining system with a puncture resistant geotextile underlay. Miles Water Engineering Ltd will be providing the products used in the repair scheme due to their early contractor involvement input.

Stirling Maynard’s design scheme takes recommendations from the Environment Agency to incorporate a combined leak detection and gas ventilation system below the liner’s surface. The liner itself is being completely replaced to help prevent future incidents and ensure the lagoon is suitable for the storage of water and liquids for years to come.