The Process of Hot Soil Sampling and Why it’s Worth the Effort

Do you like to get your hands dirty? For TerraTherm, hot soil sampling is often the defining parameter for the timeline and completion of an In Situ Thermal Remediation project, and for myself, was a great learning experience and an opportunity for me to try something new and exciting. Cleanup of contaminant source zones is what TerraTherm is known for. And those source zones that keep us in business are analyzed through soil sampling.

For most project sites, the soil is sampled at various locations before the project begins, sometimes a few times during operations, and one final confirmation round is typically completed towards the end of the project. The results from the interim and confirmatory sampling will indicate the overall removal of contaminants throughout the term of the project, as well as any contaminant redistribution within the treatment zone that may have taken place, or residual  contaminants in any cooler  spots within the wellfield that may require additional heating.

The ultimate goal for most projects is to reach a contaminant concentration standard at a particular number of locations and depths decided by TerraTherm, the regulators, the project client, and any other involved parties. The locations where soil samples are collected are often selected based on a few parameters. Cooler locations in the wellfield would indicate a lower opportunity for the contaminants in that area to volatilize and be processed through the treatment system, thereby  leaving some contaminants in the soil until proper heating has been achieved. Also, locations in the wellfield that showed heavier contaminant concentrations during the first round of soil sampling before project initiation would also be ideal places to sample throughout the course of the project. This would help to get a worst case understanding of the status of the remedy.

drill rod

Drillers extracting drill rod from core barrel in preparation for soil sample collection with sample cores.

Hot Soil Sample Cores cooling in an ice bath before sample is taken.

Hot Soil Sample Cores cooling in an ice bath before sample is taken.

The process of collecting soil samples can be very tedious and time consuming. Depending on where the team is required to sample and how deep they must drill to collect a sample, it can take hours to drill, extract the sample cores, cool the cores, and collect the samples using the appropriate containers. Bedrock and other obstructions can make it difficult to collect samples at the required depths, making it very import to understand the geology of the site you are working on. Other obstructions in the wellfield (ie. manifold piping, extraction wells, injection wells, wiring), and elevation changes can create a big challenge in getting the drill rig into the wellfield and to the desired sampling locations. Sometimes a crane is even required to place the drill rig at the sampling location due to lack of an alternate route and to prevent damage to any equipment in the wellfield.

Hot soil sampling can also be a very dangerous activity as it involves drilling deep into the subsurface that is often heated to at least 100°C. There is potential for steam to form from heated, and potentially contaminated, groundwater once the sampling well is drilled, as well as the risk of being burned while handling hot sampling cores when they are removed from the subsurface. The appropriate Personal Protective Equipment (PPE) is always worn by all parties that are participating in the sampling event to prevent exposure and injury. Heavy equipment handling also demands a great deal of planning and caution be taken during drilling activities.

All the hard work that goes into the hot soil sampling process is well worth the effort however, because it provides the project team with a direct result of what is in the ground and it proves that TerraTherm’s innovative technology does what it is designed for. Ultimately we can complete a project knowing that we have successfully met the cleanup standards for that source zone and met the clients goal for the site.

About Nikole Stone

Nikole Stone graduated from WPI in 2013 with a Bachelor of Science in Chemical Engineering, and was hired by TerraTherm in January of 2014 as a Chemical Engineer.
This entry was posted in In Situ Thermal Remediation, Other and tagged , , , , . Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>