www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 25 5.4. CONCEPTUAL MITIGATION MODEL The conceptual mitigation model considers the areas of the tunnel and mine requiring engineered controls on inflows. This is provided in Leapfrog and the following sections describe the approach. At this stage of the study (Phase 1), the conceptualised model can be split into two sub-models, with significantly different engineered solutions due to their different modes of structural control on groundwater movement: • The access development infrastructure (WUG access tunnel). This runs sub-parallel to the structural alignments and vein systems except for the Waihi Fault which is crossed nearperpendicular. The model can be further divided into the two groundwater catchments traversed by the tunnel: o The initial one-third tunnel length within the Waihou groundwater catchment flows to the south. o The remaining two-thirds tunnel length from the catchment divided into the WUG within the Otahu groundwater catchment flows to the northeast. • The WUG mine development and operation. The mining operation cuts perpendicular to the vein systems of the EG, and T-Stream Veins and stopes are developed within the veins themselves. 5.4.1. DEVELOPMENT STRATEGY Zones are identified to reflect the grouting effort required based on anticipated inflows to the tunnel: • Zone 1 Low inflow (seepage) Q <10L/min 2 forward probe holes ahead of tunnel face advancement (as required). Remedial grouting is not required. • Zone 2 Moderate inflow 10 <Q< 20L/min 4 probe holes. Remedial grouting may or may not be required. • Zone 3 High inflow 20 <Q< 100L/min 4 probe holes. Remedial grouting required. • Zone 3B Very high inflow Q >100L/min 4 or more probe holes. Such zones have yet to be identified but may be present within the ore body (as illustrated). Significant remedial grouting required. Figure 5-5 and Figure 5-6, as well as Figure 2 of Appendix A, present these zones along the tunnel alignment.
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