The Highways Agency’s latest major project – upgrading the M1 motorway between junctions 25 and 28 in Nottinghamshire – is widening a traditional three lane motorway with hard shoulder to four lanes with hard shoulder.
"So, what makes this project so special? Why have I travelled all the way up from London to write about this motorway widening scheme?" I asked.
I had walked into a room to be confronted by the top end of the project’s management team and figured that attack was probably the best form of defence.
Highways Agency project manager Tony Turton is keen to field the question. "It’s the physical constraints of the project that set it apart," he says.
The scheme has been designed and is being implemented without the purchase of new land and this has certainly put the design team under pressure on a number of fronts.
On top of that, it has not made things easier for itself by insisting on keeping the motorway running with three lanes in either direction throughout the duration of the project.
"Having no contra-flow was one of the things that really clinched the deal," says head of supervision for consultant Scott Wilson/Arup, Liz Sheerin. Scott Wilson/Arup is the Highways Agency’s supervision consultant for the project.
Average traffic flows through this stretch of the M1 reach about 140,000 vehicles per day and it was felt that using a contra-flow was likely to prove problematic in the event of breakdowns on the carriageway as well as in the channelling of traffic flows towards exits and junctions.
So while the public gets to travel on three (albeit narrower) lanes, the contractors find themselves strung out along the narrow ribbon of verge and hard shoulder. Add to this the fact that the contractor’s haul road on the hard shoulder is also shared with the emergency services and you have a recipe for a planner’s headache.
This contract requires the most painstaking and finely orchestrated logistics because there are few if any passing places for the 600 vehicles per day that serve the project within its constricted works area. WSP design manager Steve Madge explains that the project has its own dedicated logistics manager and is regulated by Zone Manager a software package which tracks deliveries, arrivals and departures to and from site.
Work on the 23km section of motorway started at the end of October 2007, and is due to finish in Autumn 2010. The contractor is MVM, a joint venture of Morgan-Est, Vinci Construction Grands Projets, and Sir Robert McAlpine. MVM’s designer is a Gifford-WSP joint venture.
The scheme is valued at £341M and everyone involved is keen to point out that this Early Contractor Involvement (ECI) contract is the first where the target cost has come in below the projected scheme budget.
This is also the first time that French heavyweight Vinci Construction Grands Projets has worked with Sir Robert McAlpine. This type of civil engineering entente cordiale is nothing new for Vinci however; its most recent joint venture with Morgan Est on the Kincardine bridge crossing the Forth is well documented.
That notwithstanding, great effort has gone into instilling a strong, project-driven culture which proactively seeks to anticipate and confront the potential conflicts that will inevitably arise between even the closest of working partners.
Value engineering on this job has been raised to the level of a fine art. Keeping the construction within current highway boundaries was one of the crucial parameters and by extension, it impacted on every aspect of design, logistics and construction. The whole scheme was characterised by Turton as a reduced cross section design.
In essence, this widening scheme has squashed more motorway into the same frame. The compact design is achieved (among other ways) by reducing the central median cross section with a stepped concrete barrier throughout. The central street lighting is being moved to the verges as a result.
The reduced cross section design also manages to bypass the need to replace or widen a number of the existing bridges on the route. The trade-off here has been that there are several discontinuities to the hard shoulder which are closely monitored using traffic management applications such as average speed cameras and CCTV. All of this resulted in a reduction of up to 2.9m of the client’s standard dual four-lane section. Naturally, this feeds through with savings in earthworks volumes and reduced bituminous pavement areas.
Working in such a physically constrained space presented huge challenges. Aside from the logistical sophistry, the widening scheme often finds itself cheek by jowl with built up residential areas.
One bridge on the route which needs its deck extending by nearly 10m on either side is within spitting distance of houses on all four corners. The same bridge required an extension of its abutments and the addition of 16 beams weighing a total of 680t.
Extending the road surface within such narrow confines is one thing, but getting the drainage right without the luxury of space for attenuation ponds posed some difficult questions. The solution arrived at was a “rolling reservoir” created using pipes – some up to 1,200mm diameter – for 50km of new drains within the verge. The drainage has also been designed to include an allowance for extra storm water anticipated by climate change.
Hydro-demolition techniques are being employed for replacement work on the parapets of 12 bridges along the route. Jet sprays (water at 2,000psi) are used to blast back the concrete on the bridge deck to facilitate the installation of an upgraded series of parapets.
The work is being carried out by Hydro Pumps and the water used is filtered through a Siltbuster filtration tank and has its pH levels monitored before being reintroduced to the drainage system.
MVM project manager Kim Barrows adds that prioritising sustainability sees the contractors in negotiations with Polypipe in a deal which could see the drainage specialists recycling the old chipped plastic ducting and conduits retrieved during excavations and returning new pipes to site.