Présentations Colloques

    Oral Presentation
    Session 8.07: Hydrogeophysics: innovative non-invasive technologies for groundwater resources exploitation and management
    Pehme Peeter
    Temporary Sensor Deployments- a New Method for Assessing Transient Hydraulic Perturbations in Boreholes and Improved Design of Permanent Multilevel Installations
    Detailed investigations of groundwater flow through fractured rock are consistently progressing towards an increased focus on hydraulic characterization of both large and small aperture fractures, the latter having an important role on matrix diffusion processes influencing plume transport and fate. Often fractured rock investigations identify abundant fracturing in continuous core and or geophysical imaging techniques. When complementary rock core chemistry sampling and or advanced thermal techniques are available, these usually indicate numerous zones of ambient groundwater flow. With increased frequency, the next stage of investigation is the installation of a multilevel monitoring system (MLS). Inevitably the choice of which commercially available MLS to use and the details of its design (i.e. port and seal intervals) is a compromise between- the number of available ports, borehole condition and potential for blending hydro-stratigraphic units or missing key flow zones. The importance of these choices is heightened when the MLS is to be used as a sentry well or for monitoring a tracer test without adequate data to prioritize critical flow zones.**We present a temporary removable and reusable installation to monitor pressure and temperature at numerous (10 or more) discrete depth intervals in a borehole as a tool for improved understanding of the hydrodynamics surrounding rock mass and planning a permanent MLS installation. Rock core and geophysical data are used to design sampling intervals of variable length, wherein pressure transducers are deployed within spacers and then a temporary liner is used to hydraulically isolate the intervals. The transducers can be twinned with high sensitivity (0.0001 C°) temperature sensors for increased resolution of thermal variations. Once the system is hydraulically stressed, either naturally or artificially, the resulting data is used to confirm and refine the design of a permanent MLS. The temporary system is entirely reusable and reconfigurable as appropriate for another location. Data from sites in California (US) and Ontario (Can) are presented to demonstrate the process, the detailed resolution of the system, and the utility of the approach.**


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