Hydraulic Profiling Tool (HPT)
The historical thought process was that the zones of higher hydraulic conductivity would most likely also contain the larger contaminant mass. It was assumed that these zones of higher conductivity would receive the majority of the injected remediation product or produce the greatest volume of contaminated groundwater under pumping conditions. Recent data indicates that this theory of hydraulic conductivity may not be uniformly applicable across contaminated sites.
The Hydraulic Profiling Tool (HPT) now allows for economical, rapid, continuous, real-time profiles of soil hydraulic properties in fine-textured to coarse-grained material. The HPT uses a sensitive, down-hole transducer to monitor the matrix back-pressure 
response to water injection. The probe is advanced through the subsurface via traditional equipment, and relays data to the surface through a trunk line which is pre-strung in the hollow probe rods. Static pressure measurements can also be made by stopping at discrete intervals, allowing users to determine static water levels. As the HPT probe is hammered into the subsurface, it provides a detailed log of the hydraulic properties of the formation. By combining EC (Electrical Conductivity) and HPT, the investigator obtains valuable data on both grain size distributions of discrete soil horizons simultaneously with relative hydraulic permeability.
See HPT components
As the HPT probe is pushed or hammered into the subsurface, it provides a detailed log of the hydraulic properties of the formation. By combining EC (Electrical Conductivity) and HPT, the investigator obtains valuable data on both grain size distributions of discrete soil horizons simultaneously with relative hydraulic permeability.
See HPT Log
How HPT works
The HPT system is designed to evaluate the hydraulic behavior of unconsolidated materials. As the probe is pushed or hammered at 2 cm/s, clean water is pumped 
through a screen on the side of the HPT probe at a low flow rate, usually less than 300 mL/min. Injection pressure, which is monitored and plotted with depth, is an indication of the hydraulic properties of the soil. That is, a relatively low pressure response would indicate a relatively large grain size, and the ability to easily transmit water. A relatively high pressure response, however, would indicate a relatively small grain size and the lack of ability to transmit water.
A Wenner Array is integrated into the HPT probe. This allows a user to collect soil electrical conductivity (EC) data for lithologic interpretation. In general, the higher the electrical conductivity value, the smaller the grain size, and vice versa. However, other factors can affect EC, such as mineralogy and pore water (brines, extreme pH, contaminates). Conversely, the HPT pressure response is independent of these factors.
There are five primary components to the HPT system: the probe assembly, controller, pump, trunkline,and field computer. The probe assembly consists of the section that houses the 100 psi pressure transducer, water and electrical connections, and the probe body with the injection screen and electrical conductivity Wenner array.
Injecting water at a constant rate is integral to system operation. A controller box houses components that monitor and regulate the water injection rate and pressure, as well as pressure transducer signal conditioning electronics. The flow rate, up to 1000 mL/min, is set manually using a knob on the front of the unit, and a valve is present to turn on or shut off flow. A pump increases system pressure ensuring adequate flow to the screen. The pump is secured to a frame with an integrated visual flow meter, and connects to the controller using a hose with quick connect fittings on each end. Any garden hose can be used to supply the pump. Water and power are transmitted from the controller to the probe assembly via the trunkline. The probe rods must be pre-strung with the trunkline before advancing the probe.
Data collection occurs in real time by connecting the controller to the field computer. The field computer collects, stores and displays transducer pressure,flow rate and electrical conductivity,line pressure,probe rate,and diagnostic parameters, with depth.
