The method of removal of the cuttings is essential to the cleanliness of the hole. For holes deeper than 10 ft., standard rotary percussive button head bits are most commonly used. These literally pulverize the rock, producing cutting that are very fine. Many drillers prefer to blow the cuttings to the surface with compressed air but this has not been satisfactory for grout holes.
If the drilling is in moist or wet conditions (which is common practice), the cuttings will combine with the moisture to form a fine slurry, which can readily block any cracks or crevices it contacts. Although contamination of defects with at least some cuttings are avoidable, water has been found to be the most harmless flush medium for use in rock.