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Laws of nature

ROADS: A11 - New roads face an unprecedented range of ecological and environmental challenges. Dave Parker reports from Norfolk, where a £32M project is coming to terms with the current realities.

Priorities have changed in road building. Ten years ago when the then Department of Transport published a summary of the environmental statement on the A11 improvement between Roundham Heath and Attleborough in Norfolk, all looked relatively straightforward.

The indicative design drawn up by Maunsell was for a classic dualling of around 10km of single track highway, linking two existing dual carriageway sections of the very busy main route to Norwich. There would be few major structures apart from a crossing of the River Thet, even though nearly all grade separated junctions featured new overbridges.

Environmental considerations were confined to noise, water quality, loss of agricultural land and the scheme's impact on archaeology and historic features. None were seen as serious problems. Then the cutback in road building in the early 1990s took its toll, and the scheme went on to the back burner for nearly a decade.

The project has now been revived as a design and build project, carried out in partnership between the Highways Agency, its consultant Maunsell, and design and build contractor May Gurney with its consultant Babtie. But there is one very obvious difference to the original indicative design.

'There was a major rethink of the vertical alignment, ' reports May Gurney highway manager Peter Hallinan. 'The original scheme needed a vast import of fill, some 700,000m 3, thanks mainly to the use of overbridges.

Switching to underbridges wherever possible cut this down to 20,000m 3, and minimised the environmental impact on the local landscape.'

But it was the raft of new legislation that had the biggest impact on the site - the 1996 Landfill Tax, the Aggregates Tax, and most restrictive of all, the Conservation (Natural Habitats, &c. ) Regulations 1994.

'We knew we had great crested newts in several ponds along the site, ' says May Gurney project manager David Huckstep. 'We knew we would have to relocate them. What we didn't realise was how complicated the new regulations are in practice.'

Great crested newts are not just protected species, points out Maunsell site representative Ray Thomason, their habitats are protected as well. 'This means that until they are successfully relocated there's a 500m radius exclusion zone around each existing pond, which effectively stops all work in that area.'

Even though new ponds had been constructed well in advance, the site team found they had to have a newt licence issued by the Department of the Environment, Food and Rural Affairs (DEFRA) before relocation could begin. This could only be granted once DEFRA, on the advice of English Nature, had approved the proposals and the site had available the services of a licensed newt handler. Until then, most work was effectively stalled.

Such experts are usually conservationists or ecologists, and finding one who could be lured up to Norfolk took time. In fact, getting through all the new regulatory loops ate so far into the agreed two year contract period that there could have been serious implications for the construction programme.

'We had hoped to complete the majority of the earthworks last summer and minimise the effect of the Aggregates Tax when it comes into force on 1 April, ' explains Huckstep. 'In the end what really made the difference were the excellent ground conditions, which have allowed us to keep on working right through the winter.'

Top down construction of the B1111 and Stone Cross underbridges is proceeding well, reports Hallinan, as are the reinforced earth abutment walls at Sallow Lane and Snetterton interchange overbridges. All bridges feature integral construction.

Babtie site representative Norman Leyland says there has been one very positive effect of the 10 year hiatus. 'In that time there's been an almost complete change in Environment Agency thinking on road drainage.

'The original proposal included a traditional all positive drainage solution. Now, south of the river, we're discharging direct into roadside swales.'

These wide, shallow vegetated channels only work well on free-draining soils, of course.

And this one simplification hardly makes up for the newts, bats and otters and ground nesting birds, all of whose needs have to be considered. None of the site team objects to the principles of the new regulations - but it will take them, and other roadbuilders, some time to come to terms with the fine print.

Winning on aggregate

Pressures to minimise HGV movements have been almost as great a constraint on the planning of the Roundham Heath to Attleborough project as the environmental regulations. One key decision was to go for cement bound granular material (CBM) as both sub-base and roadbase, using 40mm aggregate won and processed in a new dedicated pit only metres from the site. Around 150,000t will be used in all.

'The sub-base is 150mm or 300mm of CBM1X, basically a CBM2 with relaxed grading, ' explains Huckstep. 'This has been achieving compressive strengths of up to 10N/mm 2at seven days.

Above this is 180mm of CBM5 roadbase, which goes up to 25N/mm 2at seven days.'

Final wearing course is Tarmac's Masterpave. After mixing on site at the new pit, both layers of CBM are slipformed. A Wacker compactor is used to form crackinducing grooves across the CBM at 3m centres - these are later sealed with a bitumen spray.

'This system is working well, but it simply isn't fast enough for some locations, like side roads or tie-ins, ' Huckstep reports. 'There we have to use conventional flexible construction - which means importing Type 1 aggregates.'

Using roads to bring this all the way from Derbyshire would have created more than 3,000 HGV movements. Instead, May Gurney took advantage of the nearby Snetterton Sidings - closed since 1998 - and brought all roadstone in by rail.

Digging into difficulties

There were three other challenges for the A11 project team. The first was archaeology. Investigations revealed a number of Roman and medieval remains, as well as an emergency Second World War runway. The more significant finds included a Roman corn-drying kiln, an Iron Age crossing of the River Thet and a Palaeolithic hand axe.

However it was the area's more recent history of intensive sugar beet cultivation that caused some tricky logistical problems, as Huckstep explains.

'Some of the soil is contaminated with a virus which causes the disease rhizomania in sugar beet. Even though there are now resistant forms of sugar beet available, contaminated land is worth much less than uncontaminated, so there are strict DEFRA restrictions on moving topsoil - it certainly can't be taken on to the road, and contaminated soil can't be dumped on top of uncontaminated.'

May Gurney had to install special wheel washers at access points while more than 330,000t of topsoil was removed.

Luckily, the foot and mouth epidemic never reached Norfolk, but while it raged local farmers needed constant reassurance over hygiene of new pieces of plant as they arrived on site.

By comparison, the rerouting of BT's main fibre optic link between London and Norwich, which runs along virtually the entire length of the contract, was a relatively straightforward 'logistical nightmare'. It cost £600,000.

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