USE OF FLUTETM LINER INSTALLATIONS AS A METHOD TO EXAMINE CROSS-HOLE FRACTURE CONNECTIVITY IN CRYSTALLINE BEDROCK

In many communities throughout Ontario and internationally, fractured bedrock aquifers provide a significant source of water. Discrete fracture pathways and their interconnections have a critical influence on flow in such environments. While the effective porosity of these fracture pathways can be small, the average linear groundwater velocities can be very large rendering fractured bedrock aquifers especially vulnerable to contamination. To improve our understanding of flow and transport in these environments, developing and improving fracture system characterization techniques is of foremost importance. The objective of this study is to examine an innovative method of cross-hole hydraulic testing, where flexible-impermeable FLUTe^TM liners are used to generate a new style of hydraulic pulse into the fractured bedrock aquifer. Pressure and temperature response from this hydraulic pulse is monitored in a nearby network of open boreholes. This study was conducted at a field site located in Eastern Ontario, Canada in the near surface gneissic rock of the Canadian Shield. Borehole liners were installed in six existing 4-6 inch diameter boreholes located 10-35 m apart and drilled to depths ranging from 25-45 m. The collected data have been analyzed qualitatively and quantitatively to identify hydraulic connections between source and observation boreholes and determine hydraulic parameters for the examined system, which will be compared to previous hydraulic testing (pulse interference and pumping tests). Preliminary results reveal the potential for this method to be used in crystalline bedrock environments for the assessment of cross-hole connections and also indicate areas where method refinement is necessary. This form of cross-hole hydraulic data collection is complementary to other currently employed borehole liner applications such as the removal of cross-connection at contaminated sites and the assessment of discrete fracture network parameters under natural hydraulic gradient conditions. The rapidity and convenience of this testing method may therefore provide value for future site characterization efforts.