30 CFR §50.40

1. (a)Each operator of a mine shall maintain a copy of each investigation report required to be prepared under § 50.11 at the mine office closest to the mine for five years after the concurrence.
2. (b)Each operator shall maintain a copy of each report submitted under § 50.20 or § 50.30 at the mine office closest to the mine for five years after submission. Upon request by the Mine Safety and Health Administration, an operator shall make a copy of any report submitted under § 50.20 or § 50.30 available to MSHA for inspection or copying.