30 CFR §816.101

1. (a)Except as provided in paragraph (b) of this section, rough backfilling and grading for surface mining activities shall be completed according to one of the following schedules:
   1. (1)Contour mining. Within 60 days or 1,500 linear feet following coal removal;
   2. (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. (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.
2. (b)The regulatory authority may extend the time allowed for rough backfilling and grading for the entire permit area or for a specified portion of the permit area if the permittee demonstrates in accordance with § 780.18(b)(3) of this chapter that additional time is necessary.