Atlanta-based Southern told stockholders in a regulatory filing this week that it identified the cost increases in its ongoing review of costs for the Kemper County project.

“Management has reviewed a portion of these items on a preliminary basis and has identified a minimum of $160 million in likely cost increases,” the company wrote in its report to the Mississippi Public Service Commission.

“Further material cost increases may be identified as management completes its review.”

In April, Southern said it would need to spend an additional $540 million for higher-quality piping as well as more crew members to help complete the 582 megawatt integrated gasification combined-cycle (IGCC) plant by next May.

Mississippi Power spokeswoman Amoi Geter told the Associated Press that Southern shareholders would absorb the cost increases, as a January settlement with Mississippi regulator prohibited further cost increases to customers.

Initial cost estimates for Kemper were about $2.4 billion.

One opponent of the project, Northern District commissioner Brandon Presley, called the growing costs “very disturbing”

“Not once have we received good news that things are coming in under budget,” he said.

According to Rueters, it appeared Southern made the announcement via the filing to fulfill a promise of transparency, as it had previously been accused of hiding overruns for Kemper.

Two top executives at Southern's Mississippi Power unit were replaced earlier this year after questions rose about potential withheld information.

Kemper is one of only two recent IGCC projects in the US. The other is Duke Energy’s 618MW Edwardsport plant in Indiana, completed last month about a year behind schedule.

Its costs were $3.5 billion, 75% higher than initial estimates. That facility does not capture emissions.

Estimates for Kemper total more than $4.5 billion. The company has received a $250 million grant from the US Department of Energy.