A Peabody spokeswoman said that Metropolitan resumed operations at 6pm on Sunday night after a four month idle.
"We again thank our loyal employees and their families for their patience, understanding and ongoing commitment to the mine," she said.
Grech's appointment will become effective on June 1 2021.
Peabody chairman Bob Malone said Grech's extensive operational, commercial and financial experience in mining, utilities and other fuel sources will be instrumental to Peabody's success moving forward.
Grech has over 30 years of experience in the coal and natural resources industries, most recently serving as CEO of Wolverine Fuels, a US thermal coal producer and marketer.
Prior to joining Wolverine Fuels, he served as president of Nexus Gas Transmission as well as the chief commercial officer and executive vice president of Consol Energy.
He holds a Bachelor of Science in Electrical Engineering from Lawrence Technological University and an MBA from the University of Michigan.
"I look forward to joining Peabody's talented workforce and shaping the company's strategic path forward to maximize value for all stakeholders," Grech said. "I'm impressed by the significant strides the company has made during a difficult period and am excited to further improve the competitiveness of Peabody."
Kellow will step down from his position upon the effective date of Grech's appointment.
Should Kellow be re-elected as a director at the company's upcoming annual meeting on May 6, the board expects to appoint Grech to replace Kellow and serve as a board member until the next annual meeting.
Grech is also expected to be appointed to serve on the executive committee of the board.