International Paper announced in September it was investing $300 million in the Riverdale Mill to increase its industrial packaging business, but that investment has grown to more than $550 million.

The announcement was made Monday during the Dallas County Commission meeting, where a 20-year tax abatement for the company was also approved.

“This latest number floored us all,” said Dallas County Probate Judge and Commission Chairman Kim Ballard. “It’s the biggest investment in Dallas County that I remember.”

The abatement will waive property taxes of $7,203,153 and sales and use tax of $2,488,840. The abatement does not waive education taxes. During that 20-year period, the county will receive more than $5 million for education.

“This ensures the longevity of the mill,” said Jim Bruce, manager of Riverdale Mill. “Obviously, you spend this kind of money, you’re expecting to be there a long time, and until then, it was very uncertain.”

Over the next six years, the company has agreed to pay the county $250,000 each year for a total of $1.5 million.

“The only negotiations they asked for was to give us $250,000 a year for six years with no strings attached,” Ballard said. “We get $250,000 each year to do with as we please.”

That money was agreed upon due to an existing industrial development bond, where property and education tax is not paid.

The investment will convert one of the paper mill’s two paper machines from producing uncoated freesheet paper to a high quality whitetop linerboard and container board. Bruce said the new product the plant will make is similar to boxes produce is shipped and sold in at stores, as well as packaging like Amazon uses.

“This is moving us to a different product, a product that’s growing,” Bruce said.

The plant currently makes 600,000 tons of freesheet each year. After the conversion is made, the plant will make around 400,000 tons of freesheet plus 450,000 tons of linerboard.

Construction is expected to take around 18 months, according to Bruce. He said they are awaiting permits from the state and are hoping to begin in March.

While this investment is not designed to create jobs at the plant, Bruce said it will bring in around 1,000 construction jobs.

Wayne Vardaman, executive director of the Selma and Dallas County Economic Development Authority, said the most important part of International Paper’s investment is the retention of jobs.

“Five years from now, I didn’t think this mill would be in business,” Vardaman said. “This helps that. Actually, it eliminates that.”

Vardaman said International Paper is the county’s largest employee with around 750 employees.

Riverdale Mill celebrated its 50th anniversary in 2016.