- (a) After July 1, 1971, when any coal mine is worked out or indefinitely closed, such mine openings shall be properly sealed within ninety days after the mine is abandoned.
- (b) Mines temporarily inactive for less than ninety days shall be adequately fenced with conspicuous signs prohibiting the possible entrance of unauthorized persons.
- (c) Shaft openings shall be effectively capped or filled. Filling shall be for the entire depth of the shaft. Caps shall consist of a six inch thick concrete cap or other equivalent means approved by the director.
- (d) Caps shall be equipped with a vent pipe at least two inches in diameter extending for a distance of at least fifteen feet above the surface shaft.