HSA Drilling

The most common method Geotechnical engineerings utilize for obtaining soil samples and evaluating the subsurface conditions at a project site is hollow stem auger (HSA) drilling. Typically a 3 1/4" diameter auger will be advanced with a drill rig which can either be mounted to the back of a truck or ATV or track mounted type vehicle. The auger will be advanced with soil samplers advanced at regular intervals to obtain soil samples. The depth of the soil borings will depend of the type of construction that is proposed. For example, deeper borings would be required for a multi-story building than for a one story wood framed structure. Typically boring depths will range from 15 feet to 50 feet below the ground surface. However, it extreme situations borings have been advanced to depths of 200 feet or more below the ground surface.

...(and no we are not drilling for oil).

One challenge can be sands blowing into the augers below the groundwater table. To combat this, the augers can be filled with a mud water mix to prevent the inflow of water and soil into the augers while drilling. Typically a circulation tank will be placed next to the auger and the slurry will be pumped down the hole as the auger is advanced.