Appledore pumping station is an Environment Agency (EA) asset situated on the Romney Marsh in Kent. The pumping station built in the late 1940’s, operated two axial flow pumps.
The pumps were run far beyond their design life and when eventually deemed inoperable, they were removed. Three small temporary submersible pumps were put in place to maintain the levels.
The EA set some stringent parameters on the design criteria. The pumps must be fish friendly, use the most efficient pumping technology to pass 500 litres per second, per pump and most challenging of all, maintain the current winter levels in the drain.
The pumping station was built with axial flow pumps, operating on suction. One of the benefits of this is that the intake sump can be relatively shallow. The shallow intake design created a challenge, as maintaining the axial pumps impellor position is undesirable because it relies on vacuum pumps to prime the system.
Various parties, looked at the problem and could not find a way to install bowl pumps as getting the impellor submergence required to prevent cavitation simply was not possible.
The options seemed simple; either:
1) Allow the drain level to be 500mm deeper than it was designed to be
2) Major civil works to deepen the pump sump
3) Install the new pump as per the 1948 design and accept the use of a vacuum pump
Immediately option 1 could be discounted as this would flood considerable areas of Romney marsh, option 2 was economically unviable and option 3 deeply undesirable.
ACE were invited to take a look around the pumping station. ACE quickly spotted an option which could work, the option was modelled by their partners, Pentair Nijhuis using their in house CFD software. The CFD models showed the solution worked and ACE had an option which enabled exactly what the customer required, a fish friendly submersible pump which would not require alteration to the pumping station forebay.
The Environment Agency had another requirement which must be met, two lines of flood defence. ACE are renowned for their HDPE pumped flap valves; these valves are robust enough to have high velocities pumped through them, yet light and virtually buoyant neutral keeping the head loss extremely low. The low head loss reduces the amount of power the pumps require to pass the water through the valve. The HDPE flap valve also reduces the carbon footprint further when compared to cast iron alternatives.
Usually in these situations the second line of defence is in the form of an automated knife gate. ACE offered a much more robust and cost-effective solution in the form of our WaStop. The WaStop is an in-line check valve which could be installed directly behind the flap valve on the outfall thus providing two passive lines of flood defence with virtually no maintenance requirements.
As ACE delivered the project, we had a surprise visitor in the form of a ferret! This really was the cherry on the top for our site team who enjoyed looking after it whilst waiting for the RSPCA to collect it.
ACE would like to thank the EA’s South East MEICA team who were great to work with, providing substantial input and guidance during the technical discussions around the works information and throughout the delivery of the scheme to ensure it met all expectations.