WRIGHT, Wyo., Nov 30, 2009 -- Thunder Basin Coal Company's Black Thunder mine surpassed 571 days and 4.0 million employee-hours without a single lost-time injury on Nov. 20, 2009.

"The dedicated workforce at Black Thunder mine has shown that together we can achieve a perfect zero in safety incidents," says Kenneth Cochran, president and general manager of Arch's Thunder Basin. "This record-setting safety achievement highlights one of the core values upheld throughout the Arch Coal family of companies."

Black Thunder's 1,600 employees produce roughly 12 percent of the annual U.S. coal supply from the single largest coal-mining complex in the world. Black Thunder mine is located in the Powder River Basin near Wright, Wyo.

St. Louis-based Arch Coal, Inc. (NYSE: ACI) is the second largest U.S. coal producer. Through its national network of mines, Arch supplies cleaner-burning, low-sulfur coal to fuel roughly 8 percent of the nation's electricity. Arch attained an overall safety record in 2008 that was three times better than the national coal industry average, representing the company's best year on record as measured by total incident rate and lost-time incident rate.