The proposal would see the distilling of the blend’s pot still and malt whiskeys - traditionally sourced from distilleries across Ireland such as Midleton Distillery in County Cork - move to Clonminch in County Offaly, two miles from Tullamore.
The grain whiskeys used in the Tullamore Dew recipe will continue to be sourced from distilleries around Ireland.
The building works, which are set to take two years to complete, have been welcomed by Offaly County Council but are still subject to planning permission.
The investment into the 58-acre site has been driven by what the group describes as “rapid growth” in consumer demand for Irish whiskey in the US and emerging regions such as Germany, Sweden and Eastern Europe.
William Grant bought Tullamore Dew from C&C in July 2010 for £300m and claims to have overseen 15% growth in its first full year of ownership with sales reaching 700,000 nine-litre cases.
Stella David William Grant & Sons’ chief executive said: “This investment by William Grant & Sons underpins our long-term commitment to Tullamore Dew, the town of Tullamore and Ireland. We’re excited about bringing whiskey distilling back to Tullamore Dew’s roots for the first time in almost 60 years.”
The production facility and visitor centre – which opens in September 2012 – will see the brand employ about 25 people in and around Tullamore, while the building programme would support 100 construction jobs over two years.
William Grant said bottling will continue at its current packaging facility in Clonmel, where more than 60 people are employed.
According to William Grant the location of the new Clonminch site offers a “plentiful supply of natural, quality spring water from the nearby Slieve Bloom mountains”.
William Grant & Sons’ group marketing director, Maurice Doyle, said: “Our distillery will combine traditional distillation practices with the very latest in modern and green technologies to prepare the brand for future growth, while making sure the exact same taste and quality which has made Tullamore Dew famous around the world continues to be delivered.”
Pat Gallagher, county manager of Offaly County Council, said: “William Grant & Sons has invested significantly in the brand over the past 18 months with the refurbishment of the Tullamore Dew Visitor Centre, and now with the plans to construct the distillery have shown the ultimate commitment to the region.
"Tullamore has long been famed for its production of whiskey and I look forward to the first liquid flowing from the stills.”