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Dinosaur hunters on site in Scunthorpe's Jurassic Park

EARTH MOVING EARTHMOVING

Of all the signs that times-are-a-changing for earthmoving contractors, the presence of on-site palaeontologists must be the strongest. We sent David Hayward to Scunthorpe to meet construction's own dinosaur hunters

EXCAVATOR drivers helping to reclaim the site of a vast redundant Yorkshire steelworks are currently doubling as amateur palaeontologists hunting for the remains of Scunthorpe's version of the Loch Ness monster.

Visits to the local natural history museum have taught the lads a fair bit about the fossilised bone structures of ichthyosaurs and plesiosaurs. Far from just improving their minds, it is a requirement of the job.

Every excavated bite of soil is scrutinised by the site's real palaeontologist. Toothed buckets are banned and benches cut a shallow 2 m trench just in case a fossilised marine dinosaur is lurking inside the rock.

The reason? Bang in the centre of the Scunthorpe site lies Conesby Quarry, which reclamation contractor Ascot Environmental is converting into a contaminated waste landfill site. But this is no ordinary worked-out limestone pit. It boasts a section of mudstone and ironstone strata that is likely to contain the 160 millionyear-old fossils of large seagoing reptiles or giant squid.

'There is a real possibility we will unearth at least sections of a big one, ' says client North Lincolnshire Council's land reclamation officer Mike Holden.

'So the quarry's conversion must be carried out very carefully.'

Arguably more important for the council is a further bonus in the quarry's transformation that will prove much closer to the client's wallet.

Creation of this 'in-house' landfill site, suitable to take all 6 million tonnes of contaminated land from the surrounding 267 ha steelworks site, will save the county council around £150 million.

This is Mr Holden's estimated cost of the staggering one million lorry journeys that would otherwise have been needed along up to 80 km of public roads to remove the highly contaminated soil and then pay for its dumping in suitable existing landfill sites.

For more than 70 years the giant Normanby Steelworks dominated the local landscape. Its closure in 1981 saw not only 8,000 job losses but also a sprawling wasteland rich in contaminants ranging from blast furnace slag to tars, phenols, arsenic and possibly asbestos.

The site lay derelict for over a decade until its now half-complete conversion into a commercial enterprise park turned the spotlight back onto the problematic by-products of steel production.

Even though most of the really toxic waste had been dumped together in a temporary but relatively secure mid site tip, surveys revealed that at least 4.5 million cu m of soil was contaminated. And there was no practical solution other than its removal by traditional dig and dump. 'To have to truck all this material off site, long distances to a range of acceptable licensed tips, does not bear thinking about, ' says Ascot project manager Paul Sanderson. 'It would have been so expensive to have probably proved not commercially viable.'

Fortunately there was an alternative, provided ironically by the old steelworks itself. Ironstone, needed in steel production, had been extracted from a large on-site quarry, leaving behind a 33 m-deep hole capable of taking all the reclamation's contaminated soil.Only if exceptionally hazardous special wastes are discovered will these need taking off site to a high-security tip.

The cost of converting the quarry into a suitably lined engineered tip that could be licensed to accept everything bar special wastes is a comparatively modest £6 million. This leaves the project's total available funding of £23 million - most of it provided by regional development agency Yorkshire Forward - adequate to make the whole scheme economically viable.

Included in this financially lucrative solution is the further bonus that all the material needed to form the tip - clay, sand and drainage medium - can also be obtained in-house from the reclamation area itself.

'We expect to transport nothing either on or off the site, ' says Mr Sanderson.

His client is also 'fair chuffed' as Mr Holden highlights the 2 million tonnes of sand and clay reused for the tip, plus a deal to recycle a further 1 million tonnes of crushed slag into general road base.

The clay, needed to form up to 2 m-thick lining and capping layers - plus sand for future surface restoration of the tip - comes from a borrowpit adjoining the quarry.

Drainage blankets, laid above lining layers, are formed from screeded slag. Crushed concrete, from unearthed foundations, also doubles as useful filter material for general site drainage.

Previous contractors have already cleared the least contaminated areas, leaving the converted landfill hole half full. Ascot Environmental's specific £2.4 million, nine-month contract is tackling the 12 m-high waste tip containing 500,000 cu m of the most polluted soil.

Half this dump is above ground level and rows of 70 m-long trial trenches have helped classify the contents expected. The 6 m-deep, below-ground section remains uncharted, though is expected to contain more of the same plus possibly bagged asbestos.

Soon vying with the resident palaeontologist for the 'most important person on site' badge will be a biochemist, due to arrive next month when removal of the main dump gets under way. And the job specification for this newcomer carries an unusual but vital requirement.

'If the chemist is colour-blind, we are knackered, ' says Mr Sanderson bluntly. 'Every truckload of contaminated soil must be examined to determine its exact destination in the landfill site or whether it is hazardous special waste to be taken elsewhere.'

And with differing grade slags either brown or grey, arsenic and cyanide purple, tars and oils shades of black, plus asbestos wrapped in red bags, colour is a crucial guide.

For the limited quantity of intermingled domestic waste, Mr Sanderson reckons he can rely on his own experience. Dating this waste is important as older rubbish is less polluted than today's more decadent dumpers of nappies and plastics.

'Target the newspapers first, ' advises Mr Sanderson, now a dab hand at identifying The Mirror from the much younger Sun. Bottles are next in line with shape and older stopper designs an instant clue.

To receive this conglomeration of contaminants at the landfill site, Ascot is forming a double protection barrier - a containment cell within a cell.

This inner 18 m-deep bowl shaped containment area comes with its own unusually thick 2 m clay lining. It is located on top of already deposited 15 m-deep less polluted soil itself contained by the landfill's bottom 1 m-thick lining.

This so called piggy-backing technique offers - hopefully - an impenetrably long route for any leachate oozing down through two linings totalling 3 m-thick and separated by 15 m of consolidated soil.

Material in Ascot's cell will be deposited in 250 mm layers, each compacted by 19 tonne vibrating sheeps foot rollers. Even denser compaction of the clay beneath should leave the lining virtually impermeable.

This rare multi-celled containment technique allows precise mapping of each cell.

So for decades to come archeologists will be able to find the exact location of those historic Sun or Mirror newspapers.

Cleaning up at all costs

THE COST analysis of Normanby's £23 million current reclamation, compared with an estimated £150 million bill were the in-house Conesby Quarry not available for conversion into a suitable landfill site, is far from academic.

For client North Lincolnshire Council, it was not a question of choosing to decontaminate the site.

It had, by law, no option. Refuse, and ironically the council would have been forced to take itself to court for dereliction of duty.

The council inherited ownership of the site from several local district authorities, which collectively had bought the land from British Steel in the 1980s.

But under the 1995 Environmental Protection Act, all county councils are charged with seeking out contaminated sites and ordering their owners to clean them up.

'Run-off from the area was a potential source of widespread pollution, so there was no doubt we would have had to prosecute ourselves if reclamation had proved prohibitively expensive, ' reflects land reclamation officer Mike Holden.

Project details

Project: Normanby Steelworks reclamation

Client: North Lincolnshire County Council

Cost: £23.1 million over six years

Contractors, previous phases: Cheetam Hill Construction, Fox Contracting

Current phase contractor: Ascot Environmental

Contract cost: £2.4 million

Contract period: December 2002 to September 2003

Searching for ancient marine life

THE 9 m depth of mudstone, overlying 10 m of ironstone, as revealed by the working of Conesby Quarry, is part of an important geological series recognised worldwide as rich in the 160 millionyear-old sea bed fossils of marine life.

Contractors are extending the quarry area into virgin ground and it is here that palaeontologists are hoping to unearth imprints of ancient fish or reptiles.

Their expectations range from the discovery of large squid to even a plesiosaur - the long-necked marine dinosaur on which images of the Loch Ness monster are based.

So important is this history revealing source that a likely extension of Ascot's contract, when its reclamation work is complete in September, will be to remove large additional sections of the strata especially for the fossil seekers.

Excavated 'delicately' in 2 m-square chunks, a 50,000 tonne pile of rock will be created for schoolchildren, armed with archeological hammers, to crawl expectantly all over. Nearby, a second smaller pile will be reserved for research by the experts - though what guarantees that the best fossils will be in this pile is far from certain.