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TIDE ON THE TURN FOR EBBW VALE

Ebbw Vale in South Wales, which produced iron and steel for two centuries, is undergoing extensive remediation to prepare it for its new role. Damon Schünmann reports.

At 80ha, the former steelworks at Ebbw Vale in South Wales is bigger than the town from which it takes its name. 'We couldn't allow it to go unused, ' says Richard Crook, Blaenau Gwent County Borough Council's project director for reclamation of the site.

The steelworks closed in 2002 with the loss of about 1000 jobs, after which owner Corus spent three years decommissioning and demolishing the site. After reclamation, it will be redeveloped for uses including housing, commercial, medicine and teaching.

The project, on which the reclamation alone is soaking up £15M, will receive £100M of public sector investment, including £3.5M from the EU. It is hoped the private sector will stump up at least another £100M. Funding will pay for a general hospital, a college, a primary school, 450 homes and a rail link to Cardiff. There will also be 7ha for office development and 15ha to be used as public open space.

Things have moved quickly since Corus vacated the site. Crook says: 'In November last year we bought the site and began work the same day on a £400,000 culvert strengthening for the River Ebbw that runs through the valley. 'It needed to be strong before we began moving muck over it.' The culvert is up to 20m below ground level in places, and although the project team originally looked at bringing it to the surface, it was decided to be technically unfeasible.

Geraint Bowden, senior land reclamation manager for the Welsh Assembly Government, says: 'The public sector is moving very fast on this. We had an agreed masterplan for a fully designed first stage reclamation scheme with planning consent and planning approval which allowed us to move in the same day we acquired the site from Corus.

'We also had an outline business case for a local general hospital. In other projects there can be years of wrangling, but we did the whole thing while Corus was demolishing the structures and removing plant.' The council, which as client is running the scheme in a joint venture with the Welsh Assembly, has employed Halcrow to design the remediation strategy. The consultant's onsite supervisor, Sharon Stacey, says: 'There are three challenging aspects: contamination, an area of subsurface heating, and there may be potentially expansive slag that could cause ground heave [under future buildings].

'The slag is a logistical head ache as we must test samples [from each area found] and can't reuse it until we get the results, which can take up to 28 days. We are nding more than we expected and if we do find any that is expansive we will use it in areas of landscaping or in thin layers if it isn't too bad.' Where there is subsurface heating the colliery spoil is up to 15°C warmer than the surrounding ground. The precise cause of the heating is unknown but it may have been created by burning colliery spoil in the past. Halcrow believes it is now in a cooling down phase because it has either used all its fuel or oxygen.

However there is the danger of works introducing oxygen, or of the heat source spreading. To isolate the area, main contractor Walters UK awarded a subcontract to Forkers to build a grout curtain up to 25m deep to natural ground levels.

Thermocouples will also be installed to monitor ground temperature.

'We've also got hydrocarbons on the site from fuel and oil storage where there may have been spillages, ' says council project ofcer Christian Cadwallader.

So subcontractor Celtic is using bioremediation to clean the ground.

Stacey says: 'There are signicant areas of contamination and soil is being removed to another area, mixed with manure and fertiliser and aerated in windrows.' Site workers will build the new hospital, due to open in 2010, in the central Westgate portion of the site - about one quarter of the total area - where remediation is due to be completed in October. However this zone is known to have three vertical mine shafts that will need capping once they are located. There may also be shafts elsewhere in the site.

Provided the shafts are small, a geotextile will be used to cap them after any gases have been vented, although not in areas that will be built upon. Where there is building, the venting will be followed by in ling with a granular material not prone to settlement (if the shafts were not correctly lled before).

Then a mass concrete fill will go in followed by a reinforced concrete slab over the top. The shafts will still require venting afterwards to allow the escape of any further gases that may build up.

'We're doing the Westgate area first because the hospital work has been approved and that will act like a tester for the rest of the project, ' says Cadwallader. 'Dipping our toes in the water here will allow us to see how we can most efficiently do the remainder of the scheme.' Reuse of infrastructure, particularly the site's 47 basements, is a major feature of the project. This was possible because of the council's design approach, which was to develop the masterplan in tandem with the reclamation strategy.

'We have been able to use the basements which we otherwise could not have, ' says Crook. These are up to 28m deep and enclose a total void of 250,000m 3, equivalent to 1250 Olympic swimming pools. 'It's like going down inside the stairwells of a big container ship, ' he says.

It would have taken about 100,000 lorry loads to inll the basements, so the project team says its policy of best environmental practice, with reuse where possible, puts the site in the running for a Civil Engineering Environmental Quality (Ceequal) award.

'The basements are fascinating from an engineering perspective as there are so many and they are all different shapes and sizes, ' Crook says. 'We're going to reuse them where possible as they are now really part of the valley's structure.

'One will be used as a multi-storey car park while some will be heat sinks with perhaps thermal piling or water tanks. These will be cooled or heated by the ground depending on the time of year.' Bowden says: 'Some of the basements are such wonderful structures it would be great shame to break them out and ll them in.

There's the chance to use ambient ground temperature of about 14°C which is an asset. But even if we do fill some in, we can put pipes in aswell.' Crook adds: 'There have been all sorts of weird and wonderful reuse ideas for the basements like indoor parachuting. But we've also already got Gotham City here with basement bat roosts.' Reuse also avoids signicant import or export of materials, including contaminated landll.

Hard site-won material is being screened, with the nest used for grout. This material is partly retrieved from a vast concrete plinth which covers 12ha, varying in thickness from 300-800mm.

Breaking this out is a large part of the reclamation work.

The site also features made ground at depths from 0.5m to 19m, mainly consisting of slag, ash and clinker.

Some of this will require proling work - to create a 1:40 crossfall - before surface construction begins.

Given the site's history, steel was not in short supply. Contractors expect to remove signicant amounts of reinforcement from the ground, with 600m 3 to be recycled.

At the time of GE's visit in May, Walters UK had shifted about 60,000t of concrete from the slab as well as 100,000t of slag and colliery spoil. By the time the scheme ends about 2Mt of material will have been moved - the volume of a football pitch 214m high.

Other site-won material needs a little help before it can be reused.

'We're growing our own soil by importing green waste and recycling on site, ' says Crook. 'It's basically a large composting exercise where we mix it with colliery shale to create a growing medium.

'The soil ranges from PH 3.5 to 13 so we're relocating areas of the highest PH to areas where we won't be growing things and we will be carefully selecting plants for PH [tolerance] in other areas.' Half of the industrialised valley was reclaimed in the 1990s for a year-long garden festival. This area is now used mainly for housing, retail and a large park.

Work on reclamation of the second half is now well under way, and is scheduled to nish in March 2008.

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