Case study: Overpumping the Severn to manage flood risk
When damage to a retaining wall of the River Severn threatened a housing estate with flooding, a temporary pumping solution was needed while repairs were carried out
After the awful scenes of flooding that have plagued the UK over the past few months, the need to manage future flood risk diligently wherever possible has never been greater.
Heavy rains and high water levels have not only caused floods in many areas, but have also resulted in damage to locations not directly affected by the flooding, increasing the potential for more floods should periods of intense rainfall recur.
One such location is the Powys market town of Welshpool, where the damage to a retaining wall at a bend in the River Severn severely increased the flood risk to a nearby housing estate.
The Environment Agency was quick to recognise this risk and instruct Severn Trent to make urgent repairs, leading to the appointment of Abergavenny-based contractor, Alun Griffiths Civil Engineering & Construction to carry out the £½ million project.
In order to deliver the works, the Alun Griffiths team first had to create a safe working area, providing a dry environment that would enable operatives to complete the repairs and allow the mortar to dry. The company turned to pump hire specialist, Sykes Pumps, for a solution.
Explains Mike Davies from Alun Griffiths Contractors Ltd: “It was clear that we would have to overpump the river while the work was completed and we contacted Sykes Pumps because the company’s national depot network and experience of overpumping projects were critical to our needs.”
Sykes Pumps provided six 8” diesel-driven Super Wispaset 200 super silenced pumps, each with a maximum flow rate of 161 litres/second. The company delivered all six pumps to site, along with seven fuel cubes and a complex configuration of pipework totalling 420 metres, including both straight and flexible wire armoured lengths.
The pumps were set up and commissioned on site with the pipe work configured to overpump the river’sflow downstream, creating a dry working area for the Alun Griffiths team.
Comments Chris Graham from Sykes Pumps: “Not only have we been able to supply and configure pumps that will meet the operational needs of the project, but the quiet running of the pumps used at just 65dBA means that they won’t cause any nuisance noise for the nearby residents either.”
Alun Griffiths will run the pumps 24/7 while the project is ongoing as any water ingress during working hours presents a health & safety risk to the team and any water ingress out of hours could jeopardise the integrity of the completed work.
To ensure that all six pumps provide a consistently efficient pumping solution in such a demanding working environment, Sykes Pumps is sending an engineer to check and maintain the pumps every two days throughout the programme.
Chris Graham adds: “Our hire agreements usually include fortnightly maintenance visits but for this project the continuous running of the pumps and the business critical nature of the application led us to increase the level of engineering support.”
The over-pumping operation is expected to last a total of six weeks, with more than 900 litres of water per second pumped downstream day and night throughout the programme.
Mike Davies adds: “The repair work to the river embankment is critical to safeguarding Welshpool from flooding and a reliable over-pumping operation is integral to our ability to get the job done safely and quickly. Sykes Pumps has supported us with specification advice, delivery to site, setting up and ongoing maintenance, to ensure we keep the programme on track.”
- You can find out more about the role of pumps in mitigating the risks and effect of floods at The Pumping Station interactive exhibit, which is part of Utility Week Live, May 17-18 in Birmingham. Info: www.utilityweeklive.co.uk
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