Indiana Code Title 14. Natural and Cultural Resources § 14-34-6-13

(1) When the operator completes the backfilling, regrading, and drainage control of a bonded area in accordance with the approved reclamation plan, the release of sixty percent (60%) of the bond or collateral for the applicable permit area.

(2) After revegetation is established on the regraded mined land in accordance with the approved reclamation plan.  When determining the amount of bond to be released after successful revegetation has been established, the director shall retain the amount of bond for the revegetated area that would be sufficient for a third party to cover the cost of establishing revegetation and for the period specified for operator responsibility in IC 14-34-10 of establishing revegetation.  The director may not release a part of the bond or deposit under this subdivision:

If a silt dam is to be retained as a permanent impoundment under IC 14-34-10-2(b)(11), the appropriate part of the bond may be released under this subdivision if provisions for sound future maintenance by the operator or the landowner are made with the director.

(3) When the operator has successfully completed all surface coal mining and reclamation activities, the release of the remaining part of the bond, but not before the expiration of the period specified for operator responsibility in IC 14-34-10.  However, the director may not fully release a bond or deposit until all reclamation requirements of this article are fully met.