25 Pa. Code § 281.242 – Standards for successful revegetation.

(a) The standard for successful revegetation shall be the percent of groundcover of the vegetation which exists on the area affected by the facility. The Department will not approve less than a 70% groundcover of permanent plant species in the approved plan.
(b) No more than 1% of the total area may have less than 30% groundcover. No single or contiguous area exceeding 3,000 square feet may have less than 30% groundcover.

This section cited in 25 Pa. Code § 281.131 (relating to revegetation plan); and 25 Pa. Code § 281.282 (relating to cessation of operations).