M E M O R A N D U M 7 The flow factor that is used during the calculation of the effective pressure (for use in the risk matrix) is a function of the quantity of past intersected flows and the hydraulic conductivity in each zones. The factor has values between 0.25 and 1. High hydraulic conductivity and large intersected flows result in a flow factor of 1 and low hydraulic conductivities and a lack of flow intersects result in a flow factor of 0.25. 2.4 Zone summaries The information that was used to determine the likelihood of water intersects for each zone is summaries in Table 1. The likelihood of large intersects was determined based on the degree of hydraulic conductivity and the past occurrence of large flows. High hydraulic conductivity and large occurrence of flows resulted in rating “A” (Zone 5). High hydraulic conductivity zones with moderate flows resulted in a rating “B” (Zones 4, 7 and 8). No hydrograph or flow data is presently available for Zone 4, but as it is surrounded by high conductive zones and shows very poor ground based on the large percentage of RQD values below 30, it was classified as a high risk zone. Further investigation is needed to confirm this rating. Low hydraulic conductivity zones with substantial development and a lack of water intersects were classified as “E” (Zones 3 and 6). No hydrograph or flow data exists for Zones 1 and 2. These zones are located on the NW side of the FWSZ. So far no water has been intersected on this side, which resulted into a “B” rating for these zones. As no development is planned for these zones, the uncertainty inherent in this ranking is presently of no concern. Prior to planning development is these zones the low risk rating would need to be confirmed through the installation of multilevel piezometers and hydrograph analysis. Table 1: Hydraulic conductivity and water intersect likelihood for each zone. Hydraulic conductivity ratings in brackets indicate that a lack of hydrograph data to be certain. RQD values in red highlight the zones with the largest percentage of RQD values below 30. In addition to the likelihood and consequence of water intersects the eight zones have been assigned a confidence and significance ranking which is a function of the amount of available data for each zone and the degree of future development planned for each zones. The water zones good hydraulic conductivity ground water intersected % with RQD < 30 likelyhood zone 1 (no) ? 0.75 D - unlikely zone 2 (no) no 0.31 D - unlikely zone 3 no no 0.00 E - rare zone 4 (yes) ? 2.64 B - likely zone 5 yes yes 1.72 A - almost certain zone 6 no no 0.98 E - rare zone 7 (yes) yes 0.10 B - likely zone 8 yes yes 2.74 B - likely hydraulic conductivity - likelyhood
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