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Digging for victory

The project's only design and build contract faced the same unpredictable ground and weather conditions as other sections; but not the same delays. David Hayward asks why.

On paper it appeared a client's Utopian dream. A contract tendered at a third less than the expected cost; completed just a few months late with no claims bills and everyone still friendly.

On the ground it was a nightmare. Threading the motorway beneath four of the city's busiest road and rail routes, over a canal and across a 5m deep peat bog; plus completing a 1.5Mm 3muckshift during some of the wettest weather even Manchester could throw up.

That both these scenarios are true owes much to the contract form - design and build.

Alone among the four main contracts, the complex section running for 9km south east to the River Medlock from the route's junction with the M66 near Middleton, was awarded to Balfour Beatty Major Projects as a 26 month design and build contract in April 1998. And the contract was also alone in not experiencing the major delays and cost overruns faced by the other three, all let as ICE fifth edition engineer designs.

The change of contract was coincidental as the scheme was all but ready to go out as a conventional ICE5 until financial delays pushed tenders back a year.

By chance, it became the first major Highways Agency scheme to be offered not only as D&B but also requiring two envelope bidding - a fat one containing the quality offer and a slimmer second envelope enclosing the price tag.

'Initially I was dubious as my team had no experience of D&B and only a couple of months for us and our consultant Mouchel to change all the documents, ' recalls HA project manager Stephen Edwards. 'But, along with the partnering deal, it proved an excellent decision.'

His concern was shortlived as Balfour Beatty's winning £50M tender price compared favourably with the HA's own target price of over £75M. The contractor also scored top on quality with some 15 areas - ranging from experience of site staff to maintenance and environmental proposals - marked by three separate client teams.

Although Mouchel's design was well developed, Balfour Beatty's own consultant Gifford & Partners virtually started again. Several major overbridges had been completed as an advance contract, leaving seven to do, five of which Gifford changed from simply supported crossings to 'maintenance free' integral bridges. Conventional bearing and deck joints were replaced by flexible piled columns to accommodate movement.

The plan was to complete all these 'obstacles' during the first year allowing the motorway trace to be used as a haul road for a major muckshift last year. However there was something else in the way: Blackley golf course's sixth hole or, more accurately, what lay beneath it. The fairway could easily be relocated, but the up to 5m deep saturated peat on which it stood was more of a challenge.

Mouchel had proposed removing all 180,000m 3of peat and replacing it with imported fill. But Gifford instead designed a vast 900m long concrete raft, supported on 4,500 precast piles, to 'bridge' the peat and double as the motorway's road base.

'At £5M it was not the cheapest option but, if we had failed to remove all the peat by winter, we would have been left with a boggy mess right in the middle of the job, ' explains Gifford project director Martin Ramsey. 'Bearing in mind the reduced risk, the raft saved us about £1M overall.'

This novel solution also saved a potential 72,000 separate lorry journeys through local roads, by not having to remove and replace the peat - a factor that scored top quality marks at tender stage.

Similar high scores went to the proposed £10M muckshift, subcontracted to Blackwell and initially planned by Mouchel as requiring the removal from site of 800,000m 3of unsuitable material, including the peat.

Instead Gifford added environmental bunds, altered the motorway's vertical alignment by up to 300mm either way and redesigned the muckshift as a near balance cut-fill operation.

Manchester's wettest weather for decades threatened to ruin the plan by making the silty clays even more unsuitable. Liberal quantities of lime were needed to stabilise both the bunds and existing formation material along the motorway trace.

Overlaying this strengthened insitu earth with a high modulus, bitumen road base avoided the need to import most of the planned crushed stone capping layer. This eliminated even more off site wagon trips and brought the contract's overall saving to an impressive 400,000 avoided lorry journeys.

But the rain kept falling, resulting in 100% more downtime than Balfour Beatty had expected and forcing the contractor to work right through two harsh winters.

Site engineers claim that the combination of contractor design, plus an extensive partnering regime involving 200 personnel and cascading down to subcontractors, suppliers and site foremen, all helped mitigate delays. Material specifications for landscape bunds were relaxed and steeper embankment slopes allowed.

'If this had been a traditional ICE5 contract I am sure we would have faced the same sort of delays and cost rises as on the other contracts, ' argues Balfour Beatty operations director Stephen Tarr.

'Design and build left us in control and was the driver to come up quickly with cost effective, whole life solutions. The addition of partnering meant everyone had the same goal so we could focus together on problem solving.'

Ramsey reckons it was his most difficult design brief in a 30 year career. 'To have any chance of keeping to the timescale we had to keep changing the design, ' he recalls. 'Design and build allowed us to work with the contractor, minimising risk all round.'

Tarr also praises the quality approach to tendering. 'It carries risks as quality is subjective, but, without that extra envelope, we would have simply gone for the cheapest options, ' he reflects.

'Here we were encouraged to offer a better product as cost effectively as possible.'

His client agrees: 'It provided value for money and on future road contacts we are planning to make quality even more important than cost ' says Edwards. 'In 10 years' time we will all look on quality in the same way that we consider safety now.'

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