Unique Hybrid Water Attenuation Tank Installation in Snettisham | FP McCann

When unexpected groundwater levels halted the original drainage plans at the Bennett Homes 'The Spires' development in Snettisham, Canham Consulting engineers partnered with FP McCann to deliver a rapid, innovative solution within just two weeks. This video showcases the construction of a unique hybrid water attenuation system — a large, watertight precast concrete tank installed partially within the groundwater table, with an open, landscaped attenuation basin directly above it. During heavy rainfall, the underground tank fills first; during more intense storms, water backs up into the green basin above before safely draining away. As conditions ease, it all drains back down through the tank. This dual-purpose design not only provides crucial stormwater storage with full watertight guarantees, but also creates a usable public green space with wildflowers for the community during dry weather. Key highlights: • Rapid two-week turnaround from redesign to delivery • Precast concrete walls, pillars, and roof panels lifted and positioned by mobile crane • Watertight subterranean tank installed within the groundwater table • Hybrid SuDS design combining underground storage with a landscaped surface basin Learn more about FP McCann's precast concrete drainage and off-site building solutions: www.fpmccann.co.uk