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Miller in tight formation at the Edinburgh tattoo

SITE REPORT

Edinburgh City Council's new offices are situated in a World Heritage site in the city's historic centre overlooking the railway.

Not only must Miller Construction deal with one of the most difficult sites in the UK, a rigid contract also poses plenty of challenges.

Diarmaid Fleming reports

BUILDINGS for politicians have gained a bad name in Scotland following the catastrophe of the Scottish Parliament, the cost of which spiralled out of control. Its world-class engineering and architecture may stand in time as an iconic expression of the dawn of Scotland's political independence but for now the profligacy in its creation sits uneasily with a nation renowned for its shrewdness and pragmatism.

The parliament has cast a shadow of sorts over the site of Edinburgh City Council's new home, but only to ensure the same mistakes are not repeated. Painstaking negotiations took place before even a sod was turned, and a fixed price £44.6 million, 129-week contract with Miller Construction is designed to prevent similar cost overruns.

The new building, which is to be leased by the council for 20 years, is being built for client Norwich Union Life and Pensions with Morley Fund Management.

'The contract is a design and build JCT form. Costs are capped at the tender sum unless we inst ruct var iat ions, which are kept to a minimum, ' says David Fortune, NULAP surveyor and technical representative.

'Edinbu rgh City Council is very sensit ive to what happened with the Scottish Parliament building and so are we. This style of contract has been adopted so that we don't have that problem. The Scottish Parliament was built under contract management ? whatever it costs you pay ? and it was not designed at the beginning but on the hoof.

'We spent a year negotiating before we signed a contract with Miller Construction to remove all of the risks and all of the cost uncertainty before work started.' The man with the challenge of building it is Miller Construction major projects construction manager Allan Currie.

He says: 'The Scottish Parliament building is exactly why this project is set up as it is. Coincidentally, the parliament actually started off with the sum of £44 million but it grew into £430 million. Nobody was controlling the cost and the work proceeded while higher and higher specifications were being developed. We've got a contract sum of £44.6 million but it's within our purse so we have to control our costs tightly.' The council sought bids in 2001 to provide an administrative headquarters, currently housed in a variety of buildings located across the city. A bid by Railtrack and NULAP won out. Railtrack was keen to redevelop Waverley Station and maximise the potential of its site, part of which included carparking and accommodation for the British Transport Police and consultant First Engineering, which are being rehoused.

Railtrack's replacement by Network Rail later that year meant NULAP took the lead development role on the project.

Designed by architect Building Design Partnership and engineer Beattie Watkinson, the building is a reinforced concrete frame structure between three and five storeys high with two underground car parks providing around 23,000 sq m of space. Tiered glass roof ter races step back towards the south, while the building is clad with curtain walling and high-quality natural limestone. Two years of negotiations and 100 contracts were required to seal the deal before Miller began work in March 2004.

The physical challenges posed by the location are immense; the site is as difficult as one could imagine for construction.

'It's an exceptionally difficult and challenging situation but we walked into the job with open eyes, so there's no real surprise there, ' says Mr Currie.

To the north the site is bounded by the railway lines running into Waverley station, while on the east is the station car park, which remains in use. Fronting New Street and East Market Street, it's also in a World Heritage site, while an Act of Parliament imposes a 'building line' defining height restrictions.

During the planning design ? not part of the cont ractor's design r isk ? this was to pose problems.

'If we had built the building in steel, the height would have increased and breached the planning line of the Waverley Valley because of the span, ' says Mr For tune, explain ing one reason for the choice of reinforced concrete. The Act of Parliament plann ing line is h igher than that deemed acceptable by the city planners, which also led to a redesign.

'We have already had to take a f loor off and redistribute the space within the footprint ? despite the Act of Parliament line, the planning line is lower ? so even though the conceptual design was largely complete, the planners said 'no' to it, ' he adds.

All further design risk is borne by the contractor. 'Part of the risk is the design development and we said we didn't want these risks falling on to us so the contractor had to pr ice that into the cont ract, ' says Mr For tune.

Property development ceased to become a core business for Network Rail ? unlike Railtrack ? which may have led to a back-seat role on the client side but certainly did not mean it leaving the project. The core business of railway engineering has had serious implications for the job and Network Rail, through its 'outside party engineer', First Engineering, approves all works that might affect the railway.

The contractor's solution for the 12 m-deep excavation needed for the building where it bounds the railway lines was to slope the soil.

'The original design was a 45 degree cut in the ground down to between 2 and 3 m, with stone gabion baskets to retain the slope at the end. Network Rail doesn't have any commercial concerns regarding the project ? it simply looked at the solution that did most to minimise the risk to the railway. Here they decided that if the gabion baskets were to come into play then there would've had to be some ground failu re in the slope, so this idea failed. We went th rough 16 different technical solutions to solve this, ' says Mr Currie.

The solution, chosen with the contractor's engineer, Beattie Watkinson, was to form the excavation with 66 contiguous augered reinforced concrete piles. But this strategy in turn presented more problems.

'A conventional piling rig for piles of 700 to 800 mm diameter as we required is around 20 m tall, but if this was to fall or collapse it would do so over all the railway lines into Waverley Stat ion. It was proposed we could work du r ing possessions on Saturday and Sunday night when the railway would be shut ? but that would give us just four hours a night. At eight hours a week we'd be at it for two years just to get the piling done, while in the city centre we would probably get complaints on environmental grounds due to noise, ' says Mr Currie.

The solut ion provided by piling specialist Stent was a 4 m-high, small-scale, large-diameter piling rig, man enough for the job but which presented no risk to the railway in the unlikely event of it falling over. Piling is slower than using convent ional plant, although Mr Currie says a rate of one pile a day can be achieved.

The redesign comes out of the contractor's price, but the time taken to get approval from Network Rail also led to the contractor changing the construction sequence to build from the south side of the site to the north, rather than the opposite way, as or iginally envisaged.

'This bought around three months in time while we developed the solution. We have contingencies in our price but this has probably spent much of it ? it just means we have to be very strict in the way we control our design team. We are now out of the ground, where most of the risk is, so now it's all under our control. It has put us under some severe pressure but we still think we can do it, ' says Mr Currie.

With in musket shot of Edinbu rgh Castle and the military tattoo, the site operation has the efficiency of a m ilitary operat ion. Mr Currie says long-established relationships with partner contractors such as Stent and Careys pay dividends in the heat of battle.

'We have worked with our partner contractors for six or seven years, and we all know each other well and have very good working relationships with them all. No one person can plan for themselves on this job ? everything has an affect on someth ing else so we have to work together as a team or it doesn't happen, ' he explains.

Carey's managing director Pat Carey surveys the site where a team of Irish engineers and locals work into the evening on the reinforced concrete frame making up around £12 million-worth of work ? a substantial element of the contract.

'We employ our own team and a fast-track job like this helps establish us as a framework contractor in Scotland, ' says Mr Carey, fresh from the BBC Headquarters site, which his firm has also worked on. 'The biggest challenge is working near the railway and maintaining safety ? we are using a Peri formwork and multiprop system that we find quicker and faster, as well as being economical.' Access to the site is as t ight as the programme, wh ich is due for completion in September next year. Car parking areas were constructed early on to provide alternative space for railway staff and passengers, and the site has to share its entrance as an access.

'The job is now effectively landlocked. The only access for vehicles are the ones used for the car park with a height restriction of 3.5 m, ' says Mr Currie.

Like a barracks under siege, supply by air is the only answer. Tower cranes use a failsafe system to prevent collisions and causing disaster on the railway line.

Mr Currie says: 'The building is effectively the same size as the site so there is almost no area to lay down materials.

And we also can't overload the floor slabs with excessive materials, so there has to be a great degree of co-ordination in using the tower crane as efficiently as possible. Everything has to be delivered on a just-in-time basis, with materials used within a few days at most of arriving on site.' Although Edinburgh City Council is technically just a tenant, in reality it is a second client. Sustainability has been a key element to the project, in keeping with council policy. Points are awarded against key performance indicators, which have inf luenced the design and the choice of materials. Reinforced concrete was chosen over steel in par t because of its bet ter thermal conservation properties, which makes it integral to a system designed to heat or cool the building overnight.

Limestone cladding from Jura in Germany is being used partly because it can be shipped instead of taken by road, scoring higher sustainability points. The project even incorporates a mechanism for recycling rainwater to be used in cleaning.

The cont ract includes a fit-out. Almost every thing bar the furniture is included in the work before the council plans to move in after September next year.

It is a tough job but a challenge Miller Construction relishes.

'Edinburgh is our home town and this building will become a central landmark. For us to be able to take on such a strategically difficult project and pull it off successfully will ref lect on us as a construction firm ? and in many ways if we can build this, we can build anything, ' says Mr Currie.