Snavely, who has been with Arch since 2011, helped to steer the producer through its takeover of West Virginia-based miner International Coal Group.
He will continue to serve Arch through 2014 in a consultancy role for critical projects.
Bennett, with Arch since 1990 when he was hired as a senior engineer, will have responsibility for all aspects of Arch's eastern subsidiary operations as well as the eastern engineering group.
Both Bennett and Snavely will report to Arch senior vice president of operations Kenneth Cochran.
“Charles has made a significant contribution to Arch since joining the company at the time of the ICG acquisition,” Cochran said of Snavely.
“He has distinguished himself as a leader, colleague and friend, and we wish him well as he transitions into a new chapter in his life.”
Cochran said that Bennett has served as a key member of Arch's management team for many years and called him “well prepared” for his new role.
“He brings a proven track record in the areas of safety excellence, environmental stewardship, cost control, operations management, and continuous improvement, and we look forward to further progress in all these areas under Gary's leadership,” he said.