Phase 1 of the project – which is worth €20m (£16.9m) to Dunne – covers the main distillery building as well as other buildings including two warehouses. The 79-week starts straightaway and is expected to employ up to 250 workers at its peak.
Dunne will be stripping 75,000m3 of peat and forming shaped bunds with the material and carrying out a 70,000m3 cut and fill exercise in conjunction with lime stabilisation works.
All buildings and external tank slabs will be supported on precast driven piles.
Gordon Dunne, managing director of the Dunne Group said: "We look forward to building this state-of-the-art distillery for William Grant & Sons and we are very proud that in doing so it will be returning whiskey distilling to the Tullamore area for the first time in over 50 years."