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Project Focus: Severn Trent's Birmingham Resilience Project

Severn Trent is finalising plans for one of its biggest ever infrastructure projects, a £242M scheme to develop an alternative water supply for Birmingham to complement the Elan Valley Aqueduct (EVA).

The Elan Valley Aqueduct, built in 1904, supplies most of Birmingham's waterThe Elan Valley Aqueduct, built in 1904, supplies most of Birmingham's water

Drivers

- Birmingham is currently dependent for its water on the Elan Valley Aqueduct (EVA) but this needs to be maintained regularly to prolong its asset life
- An alternative supply is needed if the EVA is to be shut down for long enough to repair it effectively
- Using River Severn water instead of Elan Valley water requires a new treatment stream at Frankley to deal with pesticides and turbidity

by James Brockett

Severn Trent is finalising plans for one of its biggest ever infrastructure projects, a £242M scheme to develop an alternative water supply for Birmingham to complement the Elan Valley Aqueduct (EVA).

The aqueduct, completed in 1904, carries water using gravity from the Elan Valley Reservoirs in mid Wales to Frankley Reservoir and Treatment Works in Birmingham, providing the vast majority of the city’s water. Although the EVA is generally in good condition for a 100-year-old asset, Birmingham’s reliance on it means it is currently impossible for the aqueduct to be closed for repairs for longer than three days at a time. With substantial repairs likely to be required at some point, Severn Trent has drawn up plans for an alternative supply route which could provide security of supply and allow the EVA to be shut down for more lengthy periods.

The Birmingham Resilience Project will create a new abstraction point and pumping station on the River Severn, at Lickhill Quarry near Stourport. Water will then be pumped along a new 25km pipeline, through pipes with a 1m diameter, to Frankley Water Treatment Works.

“What this solution gives us is a new source, the Lickhill intake, which will take water from the River Severn at Stourport and pump it into Frankley,” says Severn Trent project manager Simon Hinsley. “It won’t provide an entire duplication of the capacity of the aqueduct, but it will give us about a third of what we need. Some other flow will come from our existing site at Trimpley, where we are making a cross connection to allow Trimpley water to flow into the EVA.”

While this Trimpley intake will still use a section of the EVA east of the River Severn – the East Free flow – it will leave the western section able to be shut down and maintained. The West Free flow, which has a single watercourse, is the critical section for maintenance as the eastern section contains multiple watercourses and is therefore inherently more resilient.

“Those two sources will give us about two thirds of Birmingham’s demand,” continues Hinsley. “The remainder will come from borehole sources around the city, from South Staffs Water’s Barr Beacon reservoir, and from an existing connection to our strategic grid into Birmingham. Those sources will make up the shortfall from the Trimpley and Lickhill sources to keep it going.”

When this resilience plan is in operation, the city will be drawing water from at least four sources rather than just one; and the EVA will be able to be shut down for maintenance for periods of up to 50 days at a time.

Applications pending

Severn Trent will submit its four planning applications for the project – covering the four local authority areas the project spans – in December. At around the same time it will also submit an abstraction licence of 130 megalitres per day for the new Lickhill intake; the terms of this will specify that water is only to be abstracted during the winter (between October and March) when River Severn flows are at their highest. This level of abstraction (130 M/L day) only represents around 5% of the river’s winter flow, ensuring that environmental impact will be minimal.

Work on the environment impact assessment for the project has been going on since the end of last year, and public consultation is also ongoing. If all goes to plan, construction on the pipeline will be able to start in late summer 2016.

The abstraction point at Lickhill was chosen from a list of 22 possible sites for its favourable river conditions, good access and low level of impact on the public. Meanwhile, eight possible corridors were evaluated for the pipeline route before the preferred 500m-wide corridor was chosen. This route, which runs south of Kidderminster and crosses underneath the M5, is largely rural while avoiding any particularly environmentally sensitive areas. However, it is does involve a climb of around 250m.

“The chosen solution involves a break pressure tank – effectively a mini-reservoir - at the highest point, after which the water flows down the hill into Frankley,” says Hinsley. “It’s a big pumping lift - around 250m or so to take it from the River Severn up to that high point near the M5 - so it will require some seriously powerful pumps.”

Treatment and blending

Frankley Water Treatment Works is also receiving an overhaul as part of the project in order to help it deal with the more turbid, solids-laden water expected from the River Severn. A Veolia Actiflo treatment process, which uses enhanced coagulation, has been chosen for this purpose, the first time Severn Trent will have used this solution.

Because the system will have to cope with various concentrations of EVA and River Severn water – as the two types of water blend in Frankley Reservoir when the EVA is turned off – Severn Trent has installed a £3M Actiflo pilot plant at Trimpley, including pilot scale rapid gravity filters, to assess how the plant works with different proportions of the two water types.

“When we first switch this on, we’ll be drawing down water from the holding reservoir at Frankley which is wholly made up of Elan Valley water,” Hinsley explains. “Then when we switch the Elan Valley Aqueduct off, the reservoir will start to see River Severn water from the new site, and over a period of a couple of weeks the water in that reservoir will change from EVA water to River Severn water. It’s that transition that we need to make sure it deals with.”

This pilot plant will run until February and the results will be used to inform the final operating regime put in place at Frankley. Frankley will also be fitted with a new Powdered Activated Carbon (PAC) process in order to cope with the pesticides in the new river water. The new processes will need to be approved by the Drinking Water Inspectorate before they can be implemented.

Supply chain partners

Severn Trent has recently awarded the contract for the first stage of the pipeline work to Lang O’Rourke Imtech; it is helping to develop the planning submissions and, subject to contractual terms being agreed, will also carry out the build.

Most of the engineering for the project is being provided by Jacobs and MWH Global: Jacobs is working on the pipeline, the pumping station and the environmental impact assessment, while MWH Global is leading on the Frankley Treatment Works upgrades. MWH is also running the Programme Management Office (PMO) which manages and co-ordinates the overall project.

When it won Ofwat approval for the project, Severn Trent committed to completing the project by the end of AMP6 in 2020, but its internal target for completion is a special date in 2019, as Hinsley explains.

“We’re currently working on the basis of a 3-year construction and commissioning period, and our plan is to have the physical infrastructure finished for our chief executive to come and cut the ribbon on the 21st July 2019. That’s 115 years to the day since King Edward VII opened the Elan Valley Aqueduct. I’m keenly aware of the historical legacy of the aqueduct and so I thought it was a great date to go for.”

A great admirer of the Victorian engineering that created the EVA, Hinsley says it could last another 100 years if it is given the right maintenance. Once the resilience project is completed, 50-day shutdowns will be able to be scheduled as frequently as every other winter. The new pipeline will only pump water during these shutdowns and will be dormant the rest of the time, although a small ‘sweetening flow’ will pass through the pipeline in the reverse direction for a few hours a day to prevent any stagnation.

Birmingham’s water demand overall is not increasing – lower per capita consumption, reduced business use and reduced leakage are offsetting the effect of population growth – so explaining the rationale for the project to the public is a challenge. Despite this, the reaction the project team has received from public and stakeholder engagement so far has been very positive.

“It’s fair to say that when we explain the rationale to people they are very supportive of the scheme,” says Hinsley. “That’s not to say that some people won’t have legitimate concerns about it but broadly, conceptually, people are very much in favour of doing this.”

And he adds: “We are really keen here that people understand the legacy that we are building on here, as well as the legacy that we are creating. What we are doing is tiny in comparison to what the Victorians did, but in a way, this is allowing that legacy to live on. so we’re really very aware of that historical connection, and we’re very proud of it as well - I want the whole team to feel that.”

Topic: Treatment , Water resources
Tags: Birmingham , Water supply , water treatment

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