Soil Sampling

Whether you’re a geologist, archaeologist, geo-hydrologist, work in agricultural, environmental monitoring, education or horticulture - soil sampling will be part of your research.  There are important principles to remember: sample per layer, never mix your soil layers and be sure to avoid the contamination of deeper layers by dropping soil down from higher layers.

A simple and extremely efficient tool for extracting soil samples is an auger and it may seem incredible but it’s nonetheless true that the manufacture of the “Edelman” type of hand auger is still finished by hand. Two highly trained craftsmen stand at the forge and bash away at the metal to give it the perfect shape. No machine has yet been able to replicate the skill of the craftsman.

The choice of sampling tool is determined by a number of parameters:

1. Disturbed or undisturbed: If a (semi) disturbed soil profile is acceptable then the “Edelman” type of hand auger is a good choice. It is easy to use, surprisingly effective, quick, light and cheap. If an undisturbed sample is essential then the gouge or window type of sampler is preferred. In harder soil insertion is usually carried out with a percussive mechanical hammer, either with a mechanical breaker such as the Atlas Copco Cobra TT or with a (micro) drilling rig such as the MRZB track mounted hydraulic rig.
2. Above or below the water table:  As soon as depths are achieved to levels below the water table, the hole created by the sampler will collapse.  In these circumstances, the hole will need to be cased. This is usually done with either an ABS or steel casing. Samples are then taken from within the casing which is lowered into the soil. Where sand is present this will be removed with a bailer.
3. Capture of the sample in a liner: Where samples need to be transported from site for further laboratory investigations and need to be retained in their original form and profile, liner samplers are used. Liners are usually made of polythene, acrylic or transparent PVC but can also be (stainless) steel. Special mention needs to be made for sampling of volatile organic compounds (VOC’s). By their nature, these compounds volatilise quickly and specific equipment has been developed to conform to new working guidelines which will most likely result in ISO and EN standards.
4. Specialist sampling requirements: This could include samples for the above mentioned VOC’s, pesticide residues or samples for bulk density analyses. Special kits with or without liners have been developed specifically for these applications.

Do not underestimate the usefulness of hand augers. It is easy to be seduced by mechanical devices but often the job will be done more quickly and with far less effort with hand augers. We’d go as far as to say that mechanical sampling devices should only be used as a last resort.