160(1)Where a mine heading is advancing toward a diamond drill hole, an employer shall ensure that the collar or the nearest point of intersection of the hole with the heading is securely closed off or guarded at all times while blasting is being done within 4.5 m of any possible intersection of the hole with the heading.

160(2)An employer shall ensure that the collar and any points of intersection with the heading of every diamond drill hole underground are plainly marked in accordance with subsection (3) at the time that drilling is discontinued or an intersection is made.

160(3)A mark shall consist of the single capital letter “H” measuring three hundred millimetres placed within 1.2 m of the collar or point of intersection.