(above) Steve Knobbe, HPT Design Engineer, reviews information displayed on the FC5000 Field Instrument after the completion of this interval of the push. Data analyzed from the logs can help customers quickly identify potential contaminant migration pathways, determine where to set temporary wells for slug testing, and identify zones for the injection of remediation materials.

Rapid, accurate subsurface characterization is key to any site investigation. The Hydraulic Profiling Tool (HPT) allows the user to create fast, continuous, real-time profiles of soil hydraulic properties in both fine- and coarse-grained material. The HPT uses a sensitive, downhole transducer to measure the pressure response of the soil to injection of water.

The HPT probe is advanced into the subsurface as water is injected at a constant rate, usually less than 300 mL/min. During advancement, the HPT probe automatically measures the resulting formation pressure with depth. Static pressure measurements can also be made by stopping at discrete intervals, allowing users to determine static water level. Parameters are displayed and stored on the FC5000 Field Instrument for future analysis.

The HPT probe can either be pushed or hammered into the subsurface. HPT provides a detailed log of the hydraulic properties of the formation by injecting water and measuring the pressure and flow. By combining EC (Electrical Conductivity) and HPT, the investigator obtains valuable data on lithology and permeability.

Attendees at a recent MIP (Membrane Interface Probe) Training event were given a sample of the HPT System's capabilities during one of the lunch presentations. Steve Knobbe, HPT Design Engineer, led the session.

Steve Knobbe, HPT Design Engineer, explains that the HPT and EC systems may sound similar; however, the HPT system provides more information than the standard EC system. EC measures the electrical properties of the material that it’s being advanced through, and is generally correleted to grain size. HPT measures the amount of pressure required to inject water into soil at a very low flow rate. According to Steve, “In most cases the measurements agree. However, there are some situations where mineralogy, pore water chemistry, and extreme pH conditions will affect EC measurements.” HPT measurements are independent of a soil’s electrical properties.

In short, HPT provides customers with a continuous log of high and low flow zones.

Field Applications

The Hydraulic Profiling Tool has many field applications. One primary use of this new tool is to locate and define preferential migration pathways for contaminants in the subsurface. It can also be used to target zones for injection of remediation material. In addition, the HPT can be used to select well screen intervals, evaluate locations to conduct slug tests, and measure static water conditions
across a site.