The firm is the latest in a long list of contractors appealing against fines imposed in the wake of an OFT bid-rigging probe which saw penalties of £130m imposed against 103 contractors in 2009.
The latest ruling brings to seven the number of contractors to have successfully achieved big cuts to the fines handed down.
Another 18 contractors are awaiting appeal decisions that could see further cuts in fines.
Durkan and Durkan Pudelek, now trading as Concentra, disputed several points, including liability and how the fines were calculated.
The tribunal ruled that the original fine was calculated against the wrong year’s turnover and that the OFT had failed to establish that the cover price came from the named Durkan employee.
It did however uphold the OFT in agreeing that Durkan held sway over Durkan Pudelek.
So far Kier has achieved the biggest saving from an orignal £17.9m to £1.7m fine.
Rulings so far
Kier’s fine of £17,894,438 reduced to £1,700,000.
Ballast Nedam’s fine of £8,333,116 reduced to £534,375.
Bowmer and Kirkland’s fine of £7,574,736 reduced to £1,524,000.
Corringway Conclusions’ fine of £769,592 reduced to £119,344.
Durkan’s fine £6,720,551 reduced to £2,436,000
Thomas Vale’s fine of £1,020,473 reduced to £171,000.
John Sisk’s fine of £6,191,627 reduced to £356,250.