Driving a new road through the Welsh valleys is calling for considerable environmental mitigation. Mark Hansford reports from Blackwood.
Formerly known as the Blackwood bypass, the 3.6km long Sirhowy Enterprise Way is of massive importance to the community around the long closed Oakdale Colliery in Caerphilly.
The single carriageway road will provide a strategic link between the colliery site north of Blackwood and the A472 to the south. Once the road is built, the colliery site will be developed into a business park creating 12,000 local jobs. Blackwood High Street will also gain some much needed relief.
But cutting a road through the Welsh valleys - even one just 3.6km long - was never going to be easy. In principle the scheme uses a corridor provided by the colliery's disused railway line. But the scheme still demands two crossings of the Sirhowy Valley, one to the north and one to the south of Blackwood.
To the north the chosen solution is a cable stayed bridge of some 230m span (see box).
And because the railway line bites into the hillside, cuttings have slopes of 1 in 1 in places, and 'flashy' streams cross the route.
But the biggest challenges are ecological. Advance surveys had suggested the presence of several protected species along the route, including badgers, bats, dormice and otters.
Dormice posed the biggest threat to the programme - if habitats were discovered, getting the necessary licence to disturb them could take up to five months.
Caerphilly County Borough Council is driving the scheme, which it has let as a 30 year DBFO, to concessionaire Sirhowy Enterprise Way - a 50/50 joint venture of Costain and Laing Roads. The scheme is expected to cost £34M to build, with construction carried out by design and build contractor Costain using Arup as contractor's designer.
The contract was officially awarded on 21 January 2004.
But Arup started work in September 2003 at its own risk - such was the concern over delays from the dormice.
A survey was carried out in October which confirmed their presence and the necessary licence was applied for - a demanding process.
'A lot of environmental mitigation is needed as part of the licence, ' explains Arup project director Richard Sanders.
It demanded that a raft of actions be taken. Most significant was the need to replace any habitats destroyed on a 2 for 1 basis - by area.
'Most of the habitats we were destroying were decaying anyway. So we are planting 60,000 shrubs and trees to replace the 200 or so that we have taken out, ' says Costain project director Rick Randall.
Finding space for the new habitats was also a challenge on what was already a very narrow site. 'Having to replace on a 2 for 1 basis affected the compulsory purchase orders and site boundaries, ' Sanders explains.
Fortunately, the council came up with a little extra land, and the landscaping was changed to include shrub species more suitable for dormice.
But it is not enough simply to provide a series of new habitats - they must be linked together.
So Arup and its ecology subconsultant Cresswell Associates worked up a design for a dedicated dormouse bridge.
'This is a first, ' says Arup environmental expert Simon Power. 'CCW (Countryside Commission Wales) uses projects to carry out its research. So this is experimentation and the project includes for 8-10 years of monitoring.' The dormouse bridge has to be 11m high, above streetlight level and has a 21m span to keep the support pillars well back from the road. The actual bridge 'deck' is a rope crossing formed from sisal ropes randomly woven between steel wires and enclosed within a 300mm diameter rope net tube.
The licence also called for 100 dormice nest boxes to be installed and ahead of site clearance finger-tip searches had to be conducted for dormice still in hibernation - none were found.
Additionally, roosting boxes were needed for bats and pipe crossings for otters.
Work actually began in February 2004 - ahead of the licence. 'We did actually start work without the licence, but we were confident that it was coming, ' says Costain project director Rick Randall. 'But it was quite a high risk to get started and it needed a good team and a positive approach.'
The team is on target for completion in April next year.
Bulk earthworks are complete and road surfacing is now well under way.
In total 540,000t of sandstone and mudstone has been excavated, and none of it has been wasted. By regrading slopes from 1 in 2 to 1 in 1 or 1 in 1.5, the total quantity to be excavated was reduced by 200,000t.
All good quality rock excavated has been crushed and reused as road capping along with imported slag from Newport steel works and blast furnace slag from Port Talbot. And 400,000t of lower grade material has been used to create an extension to a nearby industrial estate. The remainder has been used to construct the two cross-valley link roads.