Unfortunately, breaking drill-bits and snapping/bending a bar from time-to-time is unavoidable. Its part of the business of drilling rock.

The fact remains, tremendious hydraulic force is required to chip and cut through the rock. Time is money, and drilling is a slow process. So the driller needs to be smokin holes at a fast rate, especially with north Alaska's short summers. As Sourdough mentioned, employee and fuel costs are the biggests contributing factors to production.

So from time-to-time the driller will stumble upon a fissure in the rock struture, sometimes only a few inchs to maybe 2 feet gap. When this happens, the drill-bit suddenly breaks through the open fissure, in a split second the drill-bit slams down to the next surface area, and if the fissure is at a steep angle with a large gap, the driller can encounter some real difficult problems.

Once a fissure is encountered, the driller makes note at what deepth it is located. Fissures run at different angles for short or long distances. So it might be encountered at two feet higher or lower at the next drill spot, or it may be only a one time encounter in that location.

I've been there and I've encountered such problems. Losing drill-bits from time-to-time is going to happen