When the operator completes the backfilling, regrading, and drainage control of a bonded area in accordance with his approved reclamation plan, the release of 60 per centum of the bond or collateral for the applicable permit area.

After revegetation has been established on the regraded mined lands in accordance with the approved reclamation plan. When determining the amount of bond to be released after successful revegetation has been established, the regulatory authority shall retain that amount of bond for the revegetated area which would be sufficient for a third party to cover the cost of reestablishing reveg­etation and for the period specified for operator responsibility in section 1265 of this title of reestablishing revegetation. No part of the bond or deposit shall be released under this paragraph so long as the lands to which the release would be applicable are contributing suspended solids to streamflow or runoff outside the permit area in excess of the requirements set by section 1265(b)(10) of this title or until soil productivity for prime farm lands has returned to equivalent levels of yield as nonmined land of the same soil type in the surrounding area under equivalent management practices as determined from the soil survey performed pursuant to section 1257(b)(16) of this title. Where a silt dam is to be retained as a permanent impoundment pursuant to section 1265(b)(8) of this title, the portion of bond may be released under this paragraph so long as provisions for sound future maintenance by the operator or the landowner have been made with the regulatory authority.

When the operator has completed successfully all surface coal mining and reclamation activities, the release of the remaining portion of the bond, but not before the expiration of the period specified for operator responsibility in section 1265 of this title: Provided, however, That no bond shall be fully released until all reclamation requirements of this chapter are fully met.