We use Geoprobe’s Direct Imaging (DI) probes which are direct push probes to log important aquifer information like hydraulic permeability and electric conductivity in the borehole. The probes house detectors that acquire data sets including optical image of the borehole, hydraulic profiles and electronic conductivity in the borehole. In some cases, all these detectors can be housed in a single probe such that all these datasets are acquired concurrently and can be correlated with each other for better interpretation of hydraulic properties in the borehole. Applications of DI probes include monitoring contamination, estimating hydraulic parameters.
Some of the major DI Logs are: i) HPT Log ii) OIP Log and iii) EC Log
The HPT Log is the Hydraulic Profiling Tool Log which monitors the pressure that is needed to inject water into the soil as the probe advances into the subsurface. With an HPT Log, we can get information about the permeability of the aquifer and calculate its hydraulic conductivity.
The OIP Log is the Optical Image Profiler Log and it helps to detect non-aqueous phase liquid (NAPL) using ultraviolet fluorescence. The NAPL in the subsurface will respond to the light with fluorescence, we can not only detect where NAPL contamination is located but we can also tell in what quantity.
The EC Log measures the electronic conductivity of subsurface materials as it is pushed into the borehole and can help us tell the location of the aquifer as well as help tell the geology of formation apart. EC logging as great applications in environmental studies too and can be used to investigate contamination.
Direct Push (DP) sampling as the name implies uses direct push technology to collect samples of groundwater, soil, or even soil gas in the subsurface. As the sampler is pushed into the subsurface the sample is collected progressively. For groundwater, the sampler is used to screen the borehole at a particular location and depth so that the sample can be collected at that depth. Sampling soil or groundwater or soil gas can be used to monitor the distribution of contamination or other parameter in the subsurface. Direct Push samplers can be single tubed or dual tubed depending on the characteristics of individual sites as well as the targets for data quality.
Rock coring is used when cores are collected in the bedrock or when monitoring wells are drilled into the bedrock. They are also used in foundation studies and investigations of rock cut. Rock coring is not used in unconsolidated sediments. Because of the type of material being drilled into, diamond bits are usually attached to the core barrel for drilling.