Geologists and soil technicians use a variety of tools and methods to collect soil samples. Each method has benefits for different sample settings. The choice of which tool to use depends on the location and depth of the sample and the type of soil analysis intended for the sample. Regardless of the type of tool that you use, if you follow good sampling protocols, you are certain to obtain high quality soil samples.
Stainless Steel Spoons
The most basic soil sampling tool is a stainless steel spoon. Spoons are appropriate for soft soil samples collected within six inches of the land surface. You can also use stainless steel spoons in conjunction with other methods when you need to transfer soil from a sophisticated sampler to the collection jar. Before you collect a soil sample from a shallow depth, remove any vegetation from the spoon to ensure that the sample consists of soil only.
A hand auger is a stainless steel tube that attaches to stainless steel rods and a handle. The auger, often called a bucket, is typically 4 inches in diameter and advances into the soil when the operator twists the handle. The points on the end of the auger cut into the soil and the bucket fills with soil as the tool is advanced. Hand auger systems have rod extensions that you add as the auger advances into the subsurface. As the bucket fills, you bring it to the surface and empty the soil before continuing to the planned sample depth. You can use a stainless steel spoon to collect the sample from the auger bucket. The strength of the sample technician and the hardness of the soil limit the hand auger.
Direct Push Soil Sampling Methods
Direct push soil sampling methods are useful in areas where the sample depth is too deep for standard hand augers, the soil is very hard or speed is necessary for the project. The direct push method is useful at project sites where you are not setting permanent groundwater wells and only need soil samples from discreet areas. You can use a variety of sampling tools with the direct push drill rig. These sampling tools include a large bore soil sampler, macro-core soil sampler or a dual tube soil sampling system. Macro-core samplers are the most common for general soil sample collection. To collect the soil sample, attach the sampling tool to the direct push drill rig and allow the rig to push the sampler to the desired sample depth. You can collect the soil directly from the sampling tool.
Split-Spoon Drill Rig Methods
You can use a drill rig equipped with a split-spoon sampling tool to collect soil samples from various depths as you drill through the subsurface. This method is useful if you need a high volume of soil for the samples or if you intend to install a groundwater monitoring well at the location of the soil samples. A split-spoon sampler is a stainless steel cylinder that splits in half so that you can retrieve the soil sample. A threaded ring holds the cylinder together and attaches the sampler to the rig. A weighted hammer on the drill rig pounds the split spoon sampler into the subsurface to collect the sample.
Encore Sample Collection for Volatile Organic Compounds
Soil samples collected for volatile organic compound analysis require an additional sampling tool. This tool, the Encore sampler system, consists of a stainless-steel T-handle and plastic samplers. For shallow samples, you can use the handle to push the plastic sampler directly into the soil. The soil sample collects in the plastic sampler that serves as the sample jar. If you need to collect a sample at depth, you can use a hand auger, direct push sampler or a split spoon to bring the soil to the surface where you then use the Encore system to collect the soil sample.