Meath County Council has expressed concern about the potential impact on and damage to Newgrange and the other national monuments in the Brú na Bóinne World Heritage site from emissions from a 125m (400ft) cement stack proposed by Irish Cement.
The company, which is proposing the stack at its plant adjacent to the Boyne Valley, has not shown in the environmental impact statement what alternative locations it considered in order to minimise the visual impact of the pre-heater tower and stack, the council said.
The council was due to deliver its decision on the planning application for the extension to the plant at Platin outside Drogheda this week, but has instead issued the company with the request for further information on the application.
In addition to the new stack, the proposed extension includes the "provision of a limestone store, transport conveyors and transfer station, raw mill building, raw materials store, pre-heater tower and stack, kiln and filter grate cooler and filter, coal mill building, clinker storage silo and cement mill building".
The plan was described as "a large-scale assault on the heritage of the Boyne Valley" by a cross-Border heritage and environment forum. The Battle for the Boyne group said it was "dismayed" at what is proposed.
The planners also said the company had not explained why the stack needs to be "circa 20 metres higher than the existing stacks on site" and has asked the company to address this issue.
The council stressed the importance of "minimising/obliterating the visual impact of the proposed development from the World Heritage site".
The company has been asked to submit details about the potential negative impact and damage from emissions on decorated and inscribed stones at national monuments and ancient cultural artefacts. "You are requested to liaise with the Department of the Environment, Heritage and Local Government in this regard."
Irish Cement has six months within which to provide the information requested, otherwise it will be deemed to have withdrawn the application.