Summary of Drilling Methods to Collect Soil Samples for Infiltration Basins Summary of Drilling Methods to Collect Soil Samples for Infiltration Basins

Summary of drilling methods to collect soil samples for infiltration basins. Click on an image to enlarge.
Link to this table

Drilling Method	Description	Sample Collection Possible	Depth	Advantages	Limitations	Photo reference/credit	Example Photo
Soil Probe	Soil probes are a basic form of soil sampling, used to collect shallow or surface samples by pushing a T-shaped probe into the ground. The probe cuts a core sample smaller than the diameter of the probe body. The sample can also be collected within a liner inside the probe.	Small diameter soil surface profile	≤ 3 feet	Inexpensive Quick Easy to use	May not be able to collect enough information to determine if infiltration is possible due to depth and limited soil information collected. Unable to perform blow counts.1	Iowa State University - University Extension
Hand held or machine auger	The auger is held vertically and is driven into the ground and rotated by the handle while applying leverage. At every 30 cm of depth penetrated, the auger is taken out and the samples of the soils are collected separately for examination. This method works best in loose materials ranging from clay to sand to gravel.	Bag/jar samples of material	≤ 50 feet	Inexpensive, Easy to use. Large selection of auger types	Only suitable for unconsolidated deposits (loose materials) Slow compared to other methods Equipment can be heavy. Unable to perform blow counts1.	University of New Hampshire - Institute for the Study of Earth, Oceans, and Space
Excavation Test Pit or Trench	A pit or trench is dug manually or with an excavator to depth desired in order to visually observe subsurface soil conditions.	Grab samples or bulk samples of material	≤ 20 feet	Quick, Easy to do, Shallow exploratory drilling method	Must be onsite during excavation to coordinate locations and depth as well as observe subsurface soils and behavior, taking photos and soil samples Shallow form of subsurface drilling Must be cautious of collapsable soils when digging Requires back fill and compaction. Unable to perform blow counts1.	United States Department of Agriculture - Natural Resources Conservation Service New Hampshire
Direct Push Technology (DPT)	Geoprobe or Strataprobe is pnuematic hammer driven with continuous sampling into plastic tubes. Blow counts1 are not provided through this method. Single tube and dual tube systems are available.	Bag/jar samples of material	usually up to 60 feet but can go to over 100 feet	Minimal to no cuttings Quick and efficient Small, relatively mobile rig Continuous sampling	Unable to perform blow counts1	Minnesota Pollution Control Agency
Rotosonic	Rotosonic drilling is a method where continuous samples are taken. It is good for penetrating through most formations, but due to the ground disturbance, is not suitable for collecting undisturbed samples. Samples are brought out of the subsuface in clear plastic sleeves.	Bag samples of material	>100 feet	Continuous sampling Quick and efficient Produces little to no waste	Mobilization cost can be expensive. Unable to perform blow counts1.	United States Geological Survey - Eastern Mineral and Environmental Resources Science Center
Standard Penetration Test (SPT) using Hollow Stem Auger (HSA) drilling method	Augers act as casing for borehole (prevent caving) Center of augers is hollow for sampling	Bag/jar sample Split-spoon (or other disturbed samples) Thin-wall samples (or other undisturbed samples)	>100 feet	Augers do not need to be removed to sample Can be used above and below water table. Can collect blow counts1.	Heaving sands may clog the hollow stem auger. Can be slow when drilling in soils with cobbles and boulders.	U.S. Department of Transportation - Federal Highway Administration

¹ For information on blow counts, link here or link here for table illustrating blow counts.