The decision to upgrade the Homer City Power Plant came down in early April. 

The plant was under harsh criticism by environmental groups for the quality of the air that's emitted.

Once the Department of Environmental Protection gave the approval, the plant started to put the design to work.

It's not often cameras are let inside to see the operation of the plant, but on Tuesday, our crews were allowed in to see what the construction looks like. 

The Homer City Power Plant has been called among the dirtiest in America, but it also employs about 265 people and powers up to two million homes. 

Plant owners tell 6News the $750 million is a major investment.

"A few weeks ago, we started the ground operation for installing pollution control equipment on two of the three generating units here at the Homer City Generating Station," Senior Vice President of Communication Andy Katell said.

General Electric is powering up for a $750 million construction project that's expected to last two years.

The view from above shows where the 150-foot tall scrubbers, or nids, will be built for Chimneys one and two. 

"The primary ones you see working with steel are iron workers. They're putting in reinforcement bars and on Thursday they'll be pouring concrete over the bars and those are the foundations for the pollution control equipment," Katell explained.

Katell said the third chimney has had the pollution control equipment installed since 2001 in an effort to keep up with air control regulations.

"Over time, the government in this country has increased the regulations to clean up the air and the operators and owners of the plant wanted to remain complaint so as new regulations kick in we spend the money to install the new equipment to clean up the emissions even further," Katell said.

By 2014, Katell said tons of polluting gases like Sulfur Dioxide will be removed along with bag houses to remove any particulate matter like dust.

"And we made the calculation in the long term, this plant is going to be economically viable, competitive in the power market,  and that it made sense to invest what will be up to $750 million in the scrubber equipment," Katell said.

Katell told 6News one of the biggest challenges for GE will be to complete the project in the two year time frame.