There is no potable drill can dig frozen gravel. We have to develop drill bit for gravel. Designing bit is one of the fun part of this work. You will see the picture right side with two 1960s kids TV program shots. These underground vehicles were amazingly fast to go in the ground! I ask to Jon’s machine shop to build this “mole” type bit last year. Jon Holmgran is sharp and brilliant mechanical engineer living in Fairbanks. He was helping me more than 10 years to create new drill systems. Some system was greatly works but some one goes to bad. Anyway, this nice looking mole bit is not great digger like TV but I like it.