Sykes Pumps provides the right route in a road improvement project.
During the winter of 2015 Storm Desmond caused devastating floods in the Cumbrian Village of Braithwaite Common, where the Coledale Beck burst its banks. In addition to damaging properties, the storm caused flooding of the main trunk road that connects West Cumbria with Keswick and Penrith, causing vital road infrastructure to be closed.
With the constant threat of a repeat incident, a project has now been carried out to improve the resilience of the B5292 between Braithwaite Common and Keswick, designed to prevent the 83 metre section of road running parallel to the Beck from being compromised should the waters ever rise to flood levels again.
The three-month road improvement scheme has been carried out by Eric Wright Civil Engineering on behalf of Cumbria County Council, with the help of an over pumping solution provided by Sykes Pumps.
The scheme involved excavating under the road to the bedrock and installing a series of 700mm steel dowels into the bedrock to a depth of 600mm, before casting a new concrete base beneath the road level. This new substructure was cast in tandem with the construction of a concrete retaining wall on the Beck side of the road, and a drainage pipe that runs behind the retaining wall and under the new road build up. This infrastructure has been designed to protect the road from rising ground water and provide a defence from structural damage should the Beck flood in the future.
Throughout the programme, it was critical that the site area was protected from flooding from the Beck to protect both the integrity of the works and the safety of the Eric Wright Civil Engineering team. Meanwhile, maintaining the delicate balance of the Beck was also essential, as abstraction levels had to comply with Environment Agency requirements. To facilitate this, Eric Wright Group brought in Sykes Pumps to design an over pumping solution that would be flexible enough to manage water levels in real time.
Over Pumping Solution
The Eric Wright Civil Engineering team began by constructing a temporary dam using 18-tonne bags of aggregate. This meant that water from the Beck could be over pumped 120 metres downstream, beyond the work area.
Explains John Reilly from Eric Wright Civil Engineering: “We were granted permission to dam the Beck by the Environment Agency and part of our commitment to managing the site was to ensure that optimum water levels were maintained in the Beck at all times. This meant that we needed an over pumping solution that would manage water levels along the stretch of the Beck adjacent to the work area. We also had to ensure that water levels were never too high or too low at either side of the dammed area, to safeguard against flood risk or over-abstraction.
“We turned to Sykes Pumps to propose a solution that would offer us the flexibility to manage these complexities day-to-day while providing the potential to significantly increase flow rates should heavy rainfall affect the Beck during the 15 week programme.”
The potential for heavy rain to affect conditions in the Beck was a very real consideration as the project took place October-Dec 2018. The response from Sykes Pumps was to design an over pumping solution based on the use of two PX30N electric submersible pumps and 120m of 12 inch steel hose, while allowing for the addition of a third pump, which could be connected to the same 12 inch hose should an increased flow rate be required.
John Rajkovic from Sykes Pumps continues: “The over pumping layout was based on a maximum flow rate of 600 litres/second, with each of the two duty pumps offering a flow rate of up to 300 litres/second. This was more than sufficient to take account of normal seasonal rainfall. However, by designing flexibility into the system we were able to keep equipment and costs down while offering the possibility of an additional pump, which could be delivered from our Penrith depot and operational within a couple of hours.”
Flexibility Built In
To enable the pumps to be used with a 12” hose, the over pumping solution was designed with adapters to connect the 6” outflow to the 12” pipe. Sykes Pumps also provided the generators required to power the pumps on site, with a dedicated generator for each pump. This also provided the ability to switch to a single generator for both pumps to ensure resilience in the system at all times. The solution also included an ultrasonic control system to monitor water levels and adjust the speed of each pump in real time.
John Rajkovic continues: “We recommended ultrasonic controls to ensure that the over pumping solution was a fit-and-forget system for Eric Wright Civil Engineering, enabling them to focus on delivering the complex road strengthening programme within a very tight programme, while remaining confident that conditions in the work area would remain safe and that optimum water levels in the Beck were consistently maintained.”
This controllability requirement made submersible pumps the ideal solution for the over pumping project, as the equipment was located within the flow of the Beck, enabling accurate monitoring of flow rates and water levels. The robust 12” steel hose ensured there was ample redundancy in the infrastructure to cope with surges in flow rate and the three variable speed drive panels for each pump meant that the flow rate could be accurately adjusted to real time site requirements.
In the event, October, November and December 2018 were much drier months in Cumbria than the area is used to, which made delivery of the project more straight forward for the Eric Wright Civil Engineering team and reduced the need for variation in the flow rates.
Nick Raymond, Senior Manager, Head of Infrastructure Recovery & Major Programmes from Cumbria County Council adds: “This project has delivered vital improvements to the road network and, thanks to the over pumping solution from Sykes Pumps, it has also ensured that Coledale Beck has been unaffected by the works.”