American Electric Power today was ordered to pay over $4.6 billion for failing to adhere to the Clean Air Act, a release from the Justice Department said.

The historic pact - recorded as the largest environmental settlement to date - will force the Columbus, Ohio-based power company to pay over $1 billion in transforming its plants to make them greener by 2019. Reformations include limiting annual sulfur dioxide and nitrogen oxide emissions for its Midwestern coal plants, as well as installing additional emissions-control equipment in 2 plants.

The district court also tacked on a civil penalty of $15 million on top of $60 million in environmental mitigation.

The verdict doesn't seem to have had much of an effect on AEP shareholders, as the stock is currently trading at $47.80, up 0.19%. AEP has been on a fairly steady incline since early November, but has lately been creeping along the 42 level, using its 20-day moving average as support and its 10-day moving average as resistance.