Sampling
Well-informed remediation decisions require reliable measurement data—and we obtain that data directly at the site. Using Geoprobe®’s direct-push methods, Sensatec collects horizontal, representative samples from soil, soil air, and groundwater—without allowing contaminants to migrate from upper layers into deeper horizons, or vice versa.
Supplemented by rammed-core testing as well as the professional construction of wells and groundwater monitoring points, this creates a comprehensive, reliable database for every phase of site investigation—from the initial assessment to the monitoring of ongoing remediation measures.
Soil and Air Sampling with the Geoprobe® DualTube System DT325
The goal of this method is to obtain horizontal, representative soil air samples.
The Geoprobe® DualTube method is a sampling system used for continuous core recovery throughout the entire borehole, with the added advantage of a cased borehole.
The DT325 Soil Sampling System, designed for use with 3.25-inch drilling rods, employs a combination of a cutting shoe, casing, and a liner holder to enable efficient sampling in formations ranging from plastic clays to saturated sands.
By combining the system with a simple filter, horizontal soil air samples can be collected as needed.
Liner Sampling Using the Geoprobe Methods MacroCore, DualTube, and HSA
To ensure undisturbed soil sampling, Sensatec uses three established methods, depending on the specific task.
The Geoprobe™ Macro-Core method can be used for soil sampling that complies with standards and ensures quality control; this method prevents the migration and volatilization of contaminants while simultaneously providing undisturbed soil samples.
It is used in particular when it is necessary to extract a liner from a specific depth (sinking to the target depth without continuous core extraction).
The DualTube method is used when it is necessary to retrieve a continuous core sample throughout the entire borehole.
Depending on geological conditions, the maximum operating depth is approximately 15 m.
The Geoprobe Continuos HSA 4.25 Sampling System allows for the continuous collection of undisturbed soil samples (liners) during the drilling process. The PVC liners have a diameter of 80 mm, and a 4.25” hollow auger serves as the casing. The liner probe can be removed and reinstalled while the casing remains in place, and can be lowered to the next target depth.
Once the target depth has been reached, a branch line can be installed within the stationary protective casing, for example, to a groundwater monitoring well.
Depths of 15–20 m below ground level appear to be achievable (tested to 12 m so far).
Groundwater Surveys Using the Geoprobe Profiler SP16 Probe
The purpose of this procedure is to collect horizontal, representative groundwater samples.
The Geoprobe Screen Point 16 (SP16) Groundwater Sampler is a DirectPush probe designed to collect horizontal groundwater samples.
consists of a filter tube that is inserted into the ground within a sealed casing using a disposable tip; the filter tube is then exposed by retracting the casing and can subsequently be used for groundwater sampling.
By pulling the system out in stages, representative samples can be collected from various depths. The filter tube does not remain in the subsurface after sampling is complete.
Construction of Wells and Groundwater Monitoring Stations
Using direct-push technology and the “lost tip” system, both groundwater monitoring wells and infiltration/injection wells can be installed. This method is more cost-effective than conventional dry drilling. However, the lost-tip system is typically preferred when, due to contaminants in the soil, no soil material should be extracted during the installation of monitoring wells and/or infiltration wells, or when a minimally invasive drilling technology must be selected for other reasons.
Using hollow auger drilling (Geoprobe Continuous HSA 4.25 Sampling System) , dry rotary drilling can be performed without the need for casing, while simultaneously preventing borehole collapse. Similar to the “lost tip” system, a hollow drill string is driven down to the target depth, displacing the aquifer material laterally or conveying it to the surface via the drill bit. Unlike the DirectPush method, however, the drilling is performed using a rotary motion. Instead of a lost tip, a wooden plug is used, which is knocked out once the final depth is reached and remains in the subsurface. Depending on the soil conditions and the available drilling rig capacity, depths of up to 30 meters can be reached using hollow auger drilling.
In both methods, clay barriers ensure that individual filter sections are separated in a manner that is resistant to pressure and active ingredients, thereby preventing the formation of preferential flow paths along the lining. In addition, we recommend conducting an EC-Log survey beforehand to determine the starting points based on sound geological principles.
