Hollow-stem auger drilling is a relatively fast, easy, and cost-effective geotechnical exploration technology which employs hollow drilling augers (with center drill rods) to advance a soil boring in relatively unconsolidated/non-lithified soil and/or decomposed rock down to depths of up to effective of approximately 150-300 feet (depending upon the subsurface conditions encountered).  The hollow augers support the borehole wall from collapse while serving as a conduit to allow for the advancement and retrieval of various geotechnical soil and rock sampling tooling and/or subsurface instrumentation.  Hollow-stem auger drilling is a proven and established geotechnical exploration method, and has proven to be the gold-standard for conventional geotechnical exploration programs. 

Hollow-stem auger drilling does have limitations though, and proper considerations should be made prior to the commencement of a hollow-stem auger drilling program in order to evaluate its suitability, benefits, and risks for a given project.