When I first started in the environmental compliance business, we used bailers and ropes to retrieve water samples from wells. We eventually realized we were getting unrealistically high total organic carbon results using this method. When we did some research into the cause of this, we found that it was a specific type of rope that was contributing to the elevated total organic carbon (TOC) values.

Cutting Edge Site Investigation Tools

Today, bailers and ropes seem antiquated, and, while we’ve come a long way from those early investigative and monitoring methods, we still try to find ways to gather data more quickly, precisely, efficiently, and cost-effectively while still making better decisions.

In fact, we will be using some cutting-edge technology as we begin a large, groundwater plume delineation effort at the former Schilling Air Force Base in Salina, Kansas (click here to read more).

The Hydraulic Profiling Tool (HPT) from Geoprobe® measures the pressure required to inject a small volume of water into the soil as the probe is advanced into the subsurface. This injection pressure log is an excellent indicator of formation permeability and we will be looking for the most permeable soils where chemical transport is fastest.

Soil and groundwater investigations…made better

Recently, I sat down with Matthew Schroeder, P.E., who is Dragun’s project manager for this site, and asked him a few questions about the use of HPT at the site.

Question: How does the HPT differ from existing technology?

Traditional investigations of groundwater quality start with soil characterization by someone (typically a geologist) evaluating a soil core brought to the surface using a drill rig. The geologist would then examine the soil and classify it as a sand, silt, clay, etc. Finally, the geologist would collect a groundwater sample from a temporary or permanent monitoring well screened opposite the most permeable soil. In some investigations we have reviewed, field personnel are instructed to collect groundwater from pre-specified depths (e.g. 10, 20, and 30 feet below ground level) without knowing the geology and regardless of how quickly the groundwater moves or whether a sample can be collected.

HPT provides continuous soil permeability values with depth in real time without needing a drill rig to retrieve a soil core and then examine it. So we know the best depths to sample right away.

Question: What is the technological advantage in using HPT?

Speed is the main advantage of the HPT. For this site, decisions can be made “on the fly” for groundwater sampling depths and locations and depths for monitoring wells. HPT data could also be used to determine groundwater recovery feasibility and injection potential. The HPT technology can be paired with Geoprobe’s Membrane Interface Probe (MIP), which can detect the presence and relative concentrations of volatile organic compounds in the soil and groundwater. The MIP equipment is direct read and provides real-time results, similar to the HPT. So not only can we quickly determine the best locations to get a groundwater sample, we can also determine which locations are most impacted – in real time.

Geoprobe is planning to use some of their latest MIP technology during our upcoming work in Salina.

Question: How does the client benefit from this?

The benefits are two-fold. First, because the decision making will be happening in real time, the investigation can be conducted in a fraction of the time that a traditional investigation would take. Second, the investigation costs can be reduced through time savings in the field, lower well installation costs, and minimal waste generated from the HPT drilling process; down the road, well abandonment costs will be reduced as well.

If you would like additional information about our use of HPT in Salina, contact Matthew Schroeder (mschroeder@dragun.com) at 248-932-0228,
ext 117.