are normally drilled in patterns of 18 feet apart approximately six and three quarter inches in diameter and consists of as many as 50 holes in a pattern drilling machines have to tram around on the benches to the locations marked off to be drilled in the process of tramming from hole to hole these drilling machines have often pushed dust 44 that has piled up around the holes 40 by the drilling operation into holes 40 the amount of debris that falls into drilled holes 40 varies depending upon the amount of tramming that is done by drilling machines and by the number of holes in a pattern a truck that contains blasting agent has to back onto drilled hole patterns in order to fill the holes with blasting agent this often pushes unwanted debris into drilled holes as does high wind velocities and torrential rain especially if drilled holes 40 are in a low lying area if drilled holes 40 are sealed immediately after drilling this prevents unwanted debris 46 from falling into holes 40 thus allowing the necessary space and location for blasting agent 48 giving a greater blast the filling of drilled holes 40 is completed to the.