Sunrise spokeswoman Suzanne Jaworowski confirmed that the company has submitted an application to the Indiana Division of Reclamation to add 9,690 acres of underground area to the room-and-pillar operation.

Part of the extension may go underneath the neighboring Wabash River and into Illinois, where the producer also owns reserves. Because of that, Sunrise will also need to obtain approval of its plan from the Illinois Department of Natural Resources.

Work on the westward-moving growth plan, if it is approved, is not expected to commence until next year.

Reserves at the Oaktown mines, which lie between Sunrise’s Carlisle mine and the developing War Eagle reserve (which will now be mined through Oaktown 2), total 230 million tons.

Sunrise’s takeover of the Oaktown mines was first announced last July and closed the following month. Oaktown 1’s major customers include Hoosier Energy, Indiana Power and Light, Northern Indiana Public Service Co. (NIPSCO), and Vectren Power.