FP McCann has supplied and installed a 780 cubic metres precast concrete StormTank™ on behalf of housing developer Persimmon Homes and their civils ground worker M.V. Kelly in Newcastle-u-Lyme, Staffordshire. Sited under a landscaped area, the online attenuation tank is designed to alleviate flood risks in line with climate change conditions and storm surge events on ‘The Hamptons’ residential development
of 3 and 4 bedroom homes.

FP McCann’s StormTank™ is amongst a number of attenuation systems that are now accepted by Severn Trent Water and adoptable under the S104 approval process within Sewers for Adoption 6th and 7th Editions. StormTank™ is part of the FP McCann multi-purpose precast concrete tank range and can be designed and installed up to 6 metres high with overall dimensions to suit the client brief.

Measuring 36.8 metres long by 16.4 metres wide and at a height of 1.4 metres, ‘The Hamptons’ StormTank™ manages a storm event by capturing excess surface rainwater. The water can then released back into the online drainage system at a controlled rate thereby relieving the pressure on the main drainage network and reducing the risk of downstream flooding.

The StormTank™ designed as water class tightness 1, weighs 470 tonnes and has been constructed using over 200 individual steel reinforced precast concrete panels sections consisting of external (250mm thick) and internal (275mm thick) wall units and 120 solid roof slabs, 120mm thick. The tank is divided internally by special roof support walls with openings cast into them to allow water to flow freely between sections. Six man access opening points have been cast into designated roof sections to allow for entry for maintenance purposes. To comply with Severn Trent Water’s requirements, all elements of the StormTank™ have been positioned and constructed to achieve the required fall in the floor which in part is complete with a dry weather flow channel measuring 200mm wide by 50mm deep.

Prior to the pouring of the 250mm thick C40 concrete tank floor slab, a 100mm thick layer C20N/mm2 blinding was laid in conjunction with the precast concrete external wall installation. The panel sections manufactured at McCann’s state-of-the art precast facility in Byley, Cheshire were delivered to site over a period of 3 weeks for installation by the approved FP McCann specialist fixing team.

In conjunction with Persimmon and Manchester based EDGE consulting engineers, FP McCann value engineered the precast concrete tank system into the designated footprint by demonstrating increased performance efficiencies and associated commercial benefits over the originally detailed plastic pipe tank.

Commenting on the StormTank™ design and build, Peter Holker, Development Manager for Persimmon Homes (North West) says, “We had to take into consideration a number of factors on tank design. Robustness and long-life, low maintenance performance were key to our choice of attenuation tank. Having looked at and considered carefully a few options FP McCann’s StormTank™ fitted both the design and performance criteria. The McCann approved install team undertook the work in a timely, efficient and safe manner. On future projects, we will certainly consider similar FP McCann supply and install precast concrete StormTank™ systems.”

FP McCann’s 100 year design life StormTanks™ can be installed up to 6 metres high with no footprint size limitation and are designed for pedestrian loading through to LM1 highway loading. Internal design features can be added such as weir and baffle walls and penstocks or flap-valves can be pre-installed. Typical uses include:-
• Attenuation Tank
• StormBrake™ Chambers
• Pumping Stations
• Large CSO Chambers
• ASP Structures
• Basements
• Clean Water Storage Tank