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

Work is drawing to a close on a significant regeneration scheme in which bespoke concrete nitrile-seal drainage pipes by Marshalls Civils & Drainage have helped to mitigate potential contamination by pollutants.

Marshalls Civils & Drainage has supplied more than 140 precast concrete nitrile-seal pipes totaling 362m and in sizes ranging from 375mm to 675mm diameter to developer Marshall CDP’s Gorsey Point development in Widnes, Cheshire.

Gorsey Point is a new commercial development located on Gorsey Lane, approximately one mile from Widnes town centre. The 16-hectare site is located within the Widnes Waterfront area, a significant regeneration scheme that is transforming 145 hectares of low-quality industrial land into new commercial, residential and leisure facilities on the banks of the River Mersey, close to the new Mersey Gateway Bridge.

The former manufacturing site has been cleared to provide ‘oven-ready’ development opportunities and Marshall Construction is now constructing a three-phase development of warehousing and offices totalling approximately 700,000ft2 of space.

The site’s former industrial role has resulted in a legacy of contamination and, despite thorough remediation of the site, care still needs taking to ensure that any residual pollutants remaining underground do not leach out into the environment.

In particular, potentially aggressive petrochemical residues need preventing from compromising the site drainage system and entering local watercourses. Because of the need to protect against potential pollutants, Marshall CDP specified the use of precast concrete drainage pipes fitted with seals manufactured with nitrile rubber which is notable for being highly resistant to oil fuel and other chemicals.

The seals were manufactured for Marshalls Civils & Drainage by a specialist company in the Netherlands. Because they are specified infrequently, Marshalls Civils & Drainage offers them as a bespoke service which requires extended lead times to allow them to be produced, shipped to the UK and incorporated into the pipe manufacturing process.

Close liaison with the supply chain was therefore essential to ensure the 14-week lead time cause no disruption to the build programme. Efficient teamwork allowed site activities to be rescheduled to accommodate this without causing any delay.

In addition to the pipes, approximately 50 related pipe components, such as nitrile rockers, spigot and socket pipes for each pipe size were also supplied.

Marshall Construction’s project manager Tom Slattery said: “The pipes had to be nitrile sealed because of the contamination on the brownfield site. Everything went swimmingly – the pipes were no different to installing ordinary pipes, the only consideration was the long lead-time. “

“We were fully aware of this from the beginning and were able to make allowances in the build programme. Marshalls kept us fully informed at all times and by working closely with our supply chain we were able to plan and execute the installation smoothly and without any hiccups.”

For more information on concrete pipes please visit www.marshalls.co.uk/commercial/product/concrete-pipes