In summary
- The Storm Overflows Reduction Plan is intended to cut the number of discharges from storm overflows
- Discharges into freshwater and seawater present a risk to public health and the environment
- We increased the capacity of this site while ensuring that the existing tank would remain operational throughout
Project in numbers
55 cubic metres of additional storage required to meet new Environment Agency discharge permit regulations
0 The amount of power required to run the sustainable self-cleaning maintenance mechanism
The need
Storm overflows are intended to relieve combined sewer systems when under strain. However, this can release harmful viruses and bacteria, organic pollutants, microplastics, pharmaceuticals, nutrients, heavy metals and visible litter into rivers, lakes or the sea, presenting significant risks to public health and the environment.
As part of the Storm Overflows Reduction Plan, the Environment Agency introduced tailored storm water storage increases to wastewater sites to cut the number of discharges from storm overflows. Due to the change, this site needed to increase its capacity by 55 metres cubed to comply with the new regulations.
The solution
Replacing the existing storm tank with a larger one would have been cost-prohibitive and would have eliminated storm capacity for the duration of the programme. We proposed to construct a permanent additional tank, within the limited remaining space of the site, to operate in conjunction with the existing asset. This would allow the existing tank to remain operational and protect effluent quality throughout the duration of programme.
The new reinforced concrete tank joined to the existing tank via an overflow pipe to allow storm water to be gravity fed into it. An overflow in the new tank enables stormwater to discharge into the treatment plant’s reed beds, and a low-level outlet pipe was installed so that remaining water in the tank could be gravity drained into a sump and back into the pump chamber for processing.
We competed the new tank by installing a sustainable Eliquo Hydrok Controlled Water Flush (CWF) flushing bell; a non-powered, self-regulated method to clean sediment from storm tanks. The design, which utilises a siphon, automatically flushes stored water when the tank empties.
The benefits
- The solution enabled our client to achieve regulatory compliance by extending on-site stormwater storage capacity without removing the existing storage tank from service
- The non-powered, self-cleaning storm tank fills and drains hydraulically by gravity so requires little maintenance and power usage
- The automatic flushing bell requires zero power to run and eliminates the requirement for regular maintenance with jet-washers by operatives, saving our client considerable maintenance costs and significantly lowering the carbon footprint of the treatment plant
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