The Eden Project is the brainchild of a drop-out musician-turned-historic garden restorer Tim Smit. This CV hardly qualifies anyone to design and manage a ground-breaking construction project worth £75m, yet Smit had the foresight to second Ronnie Murning, director of London-based Land Architects, as design and development director.

In combination with the highly original architectural and structural design, Murning set in place a belt-and-braces system of risk control using a guaranteed maximum price contract. But unlike the much criticised GMP contract used on the Cardiff Millennium Stadium, he adopted the New Engineering Contract favoured by Sir Michael Latham, with the design-and-build option C.

After 12 months of negotiations, the contract was awarded to a joint venture between Alfred McAlpine and Sir Robert McAlpine, the first partnership between the two since they split in 1940. The design team, including signature architect Nicholas Grimshaw & Partners, was then novated to the contractor.

Murning adopted the NEC contract because it offered a series of safeguards not available in other forms of GMP contract. These include:

  • the appointment of a project manager (Davis Langdon Management)

  • the appointment of a supervisor (Land Architects) responsible for quality control. The supervisor operates independently of the project manager

  • an open-book policy that allows the client to monitor progress

  • a guaranteed maximum price to safeguard the client against cost overruns

  • a profit sharing scheme if the contractor brings the project in below the contract sum

  • a 10% contingency to cover provisional sums such as earthworks and steelworks.

Despite these safeguards, the project did not escape major challenges. “Our biggest problem was procuring the steel frames and fabric pillows,” says Murning. “We had three credible bids, but Mero put in the best price and probably had the most experience with spaceframe construction.

“The trouble was that Mero’s domestic subcontractor for the ETFE pillows went into liquidation. Mero was uncertain about Foiltec as an alternative, so we spent a good year negotiating the contract with Mero after we had let the main contract to McAlpines.

“We had to get the contract modified by solicitors to include a provisional sum for the spaceframe. McAlpines wouldn’t take this risk on board, so the client had to. I knew Mero had the technical expertise to do the job, but I was nervous about the cost, as Mero knew they were in a one-horse race at the time. In the end, they played with a straight bat, and we signed a contract for £13.3m, which equated to the cost plan sum of £12.5m plus our guestimate contingency sum.”

Murning says he is confident about bringing the project in on budget. “There are no exceptional financial pressures on us, and the open culture means that we are working better together as a team.”

This is a sentiment that is echoed by other members of the development team. Even Grimshaw’s project associate, Jolyon Brewis, professes to be content with the practice’s relatively subsidiary role as consultant to the main contractor.

But then, there is still 12 months to go before the GMP begins to bite …

Gardener's World