FP McCann Precast Concrete StormTank™ Installed on North Devon Housing Development

Status: Completed

Location: Barnstaple, North Devon

Division: Stormstore™

Main Contractor: M. Scoble Construction

Market Sector: Housing, Residential, Water

FP McCann has supplied and installed a 500 cubic metres precast concrete panel tank on behalf of housing developer Barratt David Wilson Homes (BDW) and their local ground worker M. Scoble Construction in Raleigh Holt, Barnstaple, North Devon. 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 Raleigh Holt residential development of 3 and 4 bedroom homes.

FP McCann’s StormTank™ is amongst a number of precast concrete attenuation systems that are now accepted by South West 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 23.7 metres long by 6.7 metres wide and at a height of 3.2 metres, the Raleigh Holt StormTank™ manages a storm event by capturing excess surface rain water. The water can then released back into the drainage system at a controlled rate thereby relieving the pressure on the main drainage network and reducing the risk of downstream flooding.

To further manage the release of flood water into the main drainage system, an FP McCann preformed DN2400 precast flow control chamber (Manhole reference S11) complete with a StormBrake™ vortex flow controller, has been installed to partner the StormTank™. The StormTank™ designed as water class tightness 1, weighs 281 tonnes and is constructed using individual external wall sections and separate roof panel units. The tank is divided internally by special roof support walls with openings cast into them to allow water to flow freely between sections. Man access opening points have been cast into designated roof sections to allow for entry for maintenance purposes. To comply with South West Water’s requirements, the StormTank™ has been benched with a 1:4 fall towards the floor which is complete with a dry weather flow channel.

Prior to the pouring of the 100mm thick C40 concrete tank floor slab, a 200mm thick layer C20N/mm2 blinding was laid in conjunction with the precast concrete wall installation. The panel sections manufactured at FP McCann’s state-of-the art precast facility in Byley, Cheshire were then delivered to site over a period of 21 days for installation by the approved FP McCann specialist fixing team.

In conjunction with Bristol based specifying design engineer Hydrock, 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, Tally Mairs, Engineering Project Manager for BDW says, “Mindful of the number of attenuation tank options available, careful consideration in conjunction with South West Water’s stringent S104 approval process, pointed us towards a precast tank. FP McCann’s robust and low maintenance StormTank™ design was our choice of attenuation system. The McCann approved installation team undertook the work in a timely, efficient and safe manner. We will certainly consider similar FP McCann supply and install precast concrete panel tanks systems on future housing and commercial projects.”

FP McCann’s 100 year design life StormTank™ 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