The lawsuit was filed in 2007 by the states of New Jersey and Connecticut, alleging that the coal-fired plant is not complying with the country’s Clean Air Act on the basis of work done many years before NRG bought the facility from GenOn.

NRG operates the plant as per the permits issued by Pennsylvania and has denied any violations of the Clean Air Act.

All the parties have agreed to reach a settlement keeping in view public interest and also to sort out the dispute in an efficient way.

NRG East Region president Lee Davis said the company acquired the plant in 2012 and started working with New Jersey and Connecticut to resolve the issue without further delay or cost to taxpayers.

"As a part of the settlement, we committed to make a significant investment in projects that are beneficial to the environment consistent with NRG’s focus on providing power in a way that is environmentally responsible, reliable and affordable," Davis added.

As per the settlement, NRG will stop using coal as a fuel at the two unit generating station by 1 June 2014, after receiving the appropriate regulatory approvals.

It will also invest $1m to benefit the environment in New Jersey and Connecticut.