The A77 near Glasgow is one of Scotland's most dangerous roads, says East Renfrewshire Council chief engineer Willy Gillan. Over the past 10 years there have been 800 accidents resulting in 34 fatalities and 134 serious injuries. 'We have had three fatalities over the past two weeks, ' he notes when he met NCE.
The usy, st moving dual carriageway is a nightmare for local traffic to access, as commuters belt along well above the national speed limit. However that should change from April, when private finance concession company Connect completes a 15.2km motorway link into the city along with a new 9.2km orbital road, leaving the existing A77 free for local access.
Building the biggest road project in Scotland means employing up to 1,000 staff on site and construction is now at a critical point. 'The success of the whole project now hinges on the Fenwick online works, ' says Connect project manager Ian Mackay. 'It is the most difficult section of the project because of all of the traffic management involved, ' he says.
The two roads, which intersect at the Maidenhill interchange are mainly new construction.
Only two sections which will sit on existing highway. The 2.5km Fenwick stretch of road at the southern end of the M77 extension overlies the existing A77, and the 700m long Philipshill flyover is being built over the existing A726 (see map).
As these two sections intersect with live traffic they present an exciting challenge to main contractor Balfour Beatty Civil Engineering and subcontractor Morrison, which has been awarded a substantial proportion of the M77 construction work. Atkins is project designer.
So far the team has successfully managed to divert traffic, keeping two lanes open in both directions for the majority of the time. On the M77 at Fenwick a complex lane switching system is in operation. The first stage of this was to construct a new section of road alongside the A77, which will be used by non-motorway traffic when the M77 opens. 'We then opened this up and ran traffic along it, which allowed us to close the northbound carriageway of the A77 and start widening it, ' says Mackay. 'At the moment we have switched the traffic onto this new carriageway and we are working on the southbound section.' Widening the existing road means extending its width to provide a hard shoulder, creating a 25m wide dual lane highway in each direction. The road must be resurfaced to motorway standard.
This section of the work is now critical as it is the last major piece of construction remaining.
'The traffic management has worked really well but the reality is that if snow hits and it's deep for the next two months then there is not a thing we can do about it, even though we have tried to make the project as weather independent as possible, ' says Mackay.
Making the project wholly weatherproof may be impossible, but one thing the team can do is use imported fill rather than relying on the existing ground to be dry enough. 'We have about 25,000m 3 to go and we will import fill for this, ' says Balfour Beatty project director David Wilkes.
Across the site 3Mm 3 of excavation has been required to level out the undulating pathway. 'The earthworks were the biggest challenge overall.
We had poor quality, small volumes of rock and the soil was saturated. We overcame this by adding lime and the soil then became an acceptable fill material.' says Wilkes.
Rock for fill and surfacing has been locally won, Wilkes reports.
'We employed Tarmac to set up a quarry on site, near North Floak.
It has made a real difference to the programme. Commercially, 200,000t of material a month simply could not have been delivered to the site, ' he says.
But in the final stages of the project, time is getting tight.
'We are going to import from now on to prevent any possible delays, ' he adds.