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Safe and Dry

Massive disruption caused by last summer’s floods has prompted an urgent review of the resilience of water assets in the UK.
There are more than 1,000 major water and sewage treatment works at high risk from flooding according to the Environment Agency – 1,145 in total in fact but there could be many more. Anglian Water alone, whose territory is the lowest lying in the UK and right in the front line of sea level rise, has 60 major assets vulnerable to a 400mm sea level rise, and more than 1,000 pumping stations under threat. Many of those assets also sit in territory that is likely, under present policy, to be lost to the sea via managed retreat schemes. If you want an example of how climate change will start affecting water company investment, and your water bills, it is clear to see from the map above.

Last summer’s floods really brought home to the public and the water industry just how vulnerable its critical infrastructure is to extreme weather patterns.

Anyone looking for an indication of the investment needed can talk to United Utilities (UU) which is ahead of the game on this after its own flooding scare of 2005 when Carlisle and its surroundings found themselves under water.

The event prompted UU to carry out a strategic flood risk review and involved the assessment last year of water supply assets in the North West.

Two hundred of them – including service reservoirs, water treatment works, pipe bridges, pumps and boreholes were found to be at risk of tidal and river flooding.

A subsequent review of wastewater assets followed this year– 400 of which are equally vulnerable. Protecting them, even to a minimum standard is likely to cost many, many millions of pounds.

“It’s relatively easy to defend the water treatment works,” says Mouchel’s flood management team leader Paul Swift who helped produce the flood risk strategy for UU. “The water enters the works in sealed pipes that can’t be polluted by flood water so it’s a question of putting an embankment defence around a works.” Even so these might have to be up to 2m high.

“But sewage treatment works are much more complicated. Flood water can enter the sewers and race into the works flooding critical equipment.”

It took 10 days to bring Mythe water treatment works in Tewkesbury back on line last summer; but it takes 12 weeks to get flooded sewage works up and running again,” he says.

UU is considering a six point scale of potential defence investment – from a minimal option which just protects the key pieces of electrical kit, through a middle option of looking after key kit and biological filters, to complete isolation of the plant from the sewage network, explains Swift.

The other alternative is to do nothing and have a back up plan. For instance, have an emergency store of important kit and spare parts. It’s a question of cost benefit analysis and risk assessment.

Part of the discussions this year, Swift says, will also be about relocation. Which plants are just so critical they have to be moved to a safer area. The final AMP 5 business plans are going to make very interesting reading.

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