That’s a tough question, because each drill we use has strengths and weaknesses, and each drill can be the best for a particular application. A very general guideline is that the best drill for the job is the largest one you can fit to the borehole location. There are however, too many exceptions to this rule to list here.
The Mini-Mole and the Geoprobe 6620 are the largest and most powerful for both environmental and geotechnical applications, while the MiniProbe is best for rapid environmental soil sampling at tighter locations or well installations where the larger machines can’t access. The Big Beaver, though lacking the higher power of the track machines, is the most versatile machine, accessing incredibly small and low overhead areas for both geotechnical and environmental sampling and is especially proficient in small indoor areas. The Geoprobe 420 is ideal for environmental soil sampling in very narrow and indoor areas where SPTs or monitoring wells are not required. The handheld rapid percussion machines are the best machines to use when you can’t fit anything larger to the borehole location.
Over the last 20 years we have drilled in the most incredibly diverse range of locations requiring small drills. Our philosophy is to consider each drill as a different tool in our toolbox. Based on this 20 year history of drilling in limited access areas, we reach for the best tool for the job.