The original scope was to lay a new Premseal membrane. However, upon inspection it was apparent that around 85 per cent of the original bitumen membrane had perished. This would have needed to be completely removed in order to apply Premseal, adding many weeks to the schedule of works.
As extending the time frame was not an option for this critical asset, Stonbury was tasked with identifying an alternative solution. It was decided with the client that a loose Flagon membrane would be the most effective solution to apply within the timeframe, as this durable material will last for a considerable number of years.
The team prepared the roof by removing the existing overburden, using a long reach excavator to remove soil from the edges of the tank to reduce time and ensure works stayed within programme. The team utilised five track barrows and two micro-diggers to minimise weight on the roof and hired a 7-tonne track dumper to minimise detrition on existing ground, saving money on the reinstatement.
The original bitumen coating was then left in place but jetted free of debris, and WLS (Waterline Solutions) were hired to lay the Flagon liner. Stonbury then applied the final membrane and overburden reinstatement. Stonbury was also tasked with the removal and sealing of the existing vents. For reinstatement detailing, the team decided to re-utilise the stripped material, which is a preferred solution if soils are suitable, saving on cost and reducing carbon footprint.
Works were programmed for eight weeks, though Stonbury would normally allow 10 for a tank of this size. However, due to the exceptional efforts from the team, all works were completed within six weeks. This project is an excellent example of out-of-the-box thinking to achieve an effective solution within a challenging timeframe.