Code of Federal Regulations Title 30. Mineral Resources § 30.816.101 Backfilling and grading:  Time and distance requirements

(1) Contour mining. Within 60 days or 1,500 linear feet following coal removal;

(2) Area mining. Within 180 days following coal removal, and not more than four spoil ridges behind the pit being worked, the spoil from the active pit constituting the first ridge;  or

(3) Other surface mining methods. In accordance with the schedule established by the regulatory authority. For States with approved State programs, schedules are subject to the State program approval process.