Contributed photo / Amanda Pedde works at a Southern Champion Tray facility in Chattanooga. The company that makes paperboard packaging products is conducting due diligence on a Riverport site to expand.

A longtime Chattanooga company is planning for more than 1 million square feet of space at a proposed new manufacturing facility in a expansion originally unveiled last year.

Also, Southern Champion Tray may over time relocate its existing factory space, for many years situated on Compress Street near downtown, to the proposed location at Centre South Riverport, according to documents filed with the state.

The company's plans are included in an Aquatic Resource Alteration Permit application for the Riverport site and weren't revealed by the maker of paperboard packaging products when the expansion was announced last August.

The company said then it plans to invest nearly $85 million in a new manufacturing plant where it will create more than 120 jobs.

The 94-year-old company, which makes products including food sleeves, trays, window boxes, and cupcake inserts, already employs over 750 people, including more than 500 in Chattanooga.

In a statement this week, the company said the permit application is part of its continued due diligence in regard to the purchase of a 54.6-acre tract at the Riverport.

"We are still finalizing plans with the expectation that diligence will be completed in May," the statement said. "One of the main reasons to consider a larger complex at Centre South is due to the space restrictions on our Compress property. However, we envision using both sites for the foreseeable future."

In the application, the company said it's looking at initially building about a 600,000-square-foot plant at the tract at the Riverport off Amnicola Highway.

Also, the company said it's eyeing two additional phases of 320,000 square feet each.

The new manufacturing facility will convert paperboard into packaging products. Construction is expected to begin in early 2021 with completion by early 2022, the company has said.

John Zeiser, SCT president and chief executive officer, said last year the proposed project would support continued expansion of its manufacturing operation in the city.

"We are bursting at the seams where we are, so we have to expand," he said. "We're blessed to be able to continue to grow in Hamilton County."

Brian Hunt, the company's chief operations officer, said at the time that the move is "a vote of confidence for every current SCT employee, as well as the 120 new employees that we will be adding."

"After 93 years of continuous growth, we are excited to build another facility to support many more years of serving customers with great packaging and distinctive service," he said.

Contact Mike Pare at Follow him on Twitter @MikePareTFP.