(a) Each operator of a mine shall maintain a copy of each investigation report required to be prepared under Sec. 50.11 at the mine office closest to the mine for five years after the concurrence.
(b) Each operator shall maintain a copy of each report submitted under Sec. 50.20 or Sec. 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 Sec. 50.20 or Sec. 50.30 available to MSHA for inspection or copying. [42 FR 65535, Dec. 30, 1977, as amended at 43 FR 12318, Mar. 24, 1978]