Minister for the Environment Alan Kelly has described a proposed €650 million hydro-electric plant which will create 400 construction jobs and 50 permanent jobs on a disused mining site as a "win-win" project.

Details of the 360MW Silvermines Hydro Electric Power Station were announced on Monday in Nenagh by Mr Kelly and members of the joint venture behind the ambitious plan, believed to be one of the largest infrastructural projects in the State’s history.

The partnership aiming to build the zero-emission plant at Silvermines in north Tipperary includes Irish developer Siga Hydro, Irish construction company Roadbridge and Austrian construction and technology companies Strabag Group and Andritz Hydro.

Some feasibility work has already taken place and further, detailed, feasibility assessments will now be carried out along with a consultation programme with the local community.

Because of the scale of the plan, it will go straight to An Bórd Pleanála and the planning process is expected to start later this year and take up to two years to complete, with construction earmarked for a further four years.

Darren Quinn, managing director of Siga Hydro and the project director said they identified the need for such a plant over six years ago and chose Silvermines because of its mountainous location, the existence of an existing 70-metre deep reservoir since its mining days and proximity to the existing electricity network.

“This is a strategic project of national importance,” he said at yesterday’s launch in Nenagh.

“This is a once-off opportunity to help remediate and clean up this giant abandoned mining site by creating a new land use, something that will benefit the entire nation.”

Mr Quinn said it’s “difficult to tell” if the project will meet with local opposition but said the backers are determined to fully engage with the surrounding communities.

“We have a long process ahead of us,” he said. The first part is to do some detailed feasibility work but also, in tandem, to work with the local community. We want to be working with the local community.”

Any concerns raised to date mainly centred on the abandoned nature of the mining site, he said, which has not been used since 1993, and the project will involve the decontamination of water in the existing reservoir.

Development will include the construction of a new, second reservoir on the site and, eventually, 2.5 billion litres of water will be used in a closed system.

A five-metre thick steel pipe will be used to pump water between the two reservoirs and into an underground powerhouse which will store the turbines used to generate electricity.

Enough power will be created to supply 200,000 homes, the developers say, and the project will not include pylons as underground cabling will be used to link with existing 400KV and 220 KV lines in the area.

Alan Kelly, in whose Tipperary constituency the development will take place, said the Government’s white paper on energy recommended the establishment of such renewable energy sources.

“The total value to Ireland is expected to be about €2.5 billion,” the minister said. “It’s really something that’s necessary in our currently energy environment. The more and more we move to renewable, the more we need to move to something like this.”

The “great thing” about the project is that it will turn a “negative,” which is the abandoned mining site, into a positive, Mr Kelly said. “I believe this is a win-win at a national level but most of all, it’s a huge win-win at local level for Silvermines and Nenagh and the surrounding areas.”