Presentation on theme: "TECHNICAL REVIEW Initiated a review on the Abandonment and Restoration Plan of the Lupin Mine: –conducted August through October 2001. Team Members: –EBA."— Presentation transcript:
TECHNICAL REVIEW Initiated a review on the Abandonment and Restoration Plan of the Lupin Mine: –conducted August through October 2001. Team Members: –EBA Engineering Consultants; and, –Robertson GeoConsultants.
TECHNICAL REVIEW Objective: –Clarify technical feasibility of existing reclamation plan; and, –Initiate the process of determining viability of alternative restoration/reclamation methods.
TECHNICAL REVIEW Focused on: –Geothermal/geotechnical; and, –Geochemical database
TECHNICAL REVIEW Existing Reclamation Plan: –Flooding of areas that are currently used for water retention;and, –Mechanical covering of higher elevation tailings cells with esker material.
TECHNICAL REVIEW Review of Geothermal Data: –Extensive database; –Mine is located in area of continuous permafrost; –Mean annual ground temperatures, -6 0 C - 8 0 C; –Active layer thickness ranges from 1.0 m (undisturbed terrain) to 4.0 m (exposed bedrock).
TECHNICAL REVIEW Geothermal Data: –Reclaimed Tailings Cells; Frozen year round except for seasonal thaw; Active layer thickness ranges between 1.5-2.0 m; Thickness of active layer dependent upon amount of cover; Active layer typically penetrated 1.0 m into underlying tailings; and, Temperatures in inactive cells below 10 m depth ranged between -3.5 0 C to -7.5 0 C.
TECHNICAL REVIEW Review of Geochemical Data: –Extensive database; –Tailings characterized by high sulphide content and low neutralization capacity; and, –Exhibit a tendency to become acid generating.
TECHNICAL REVIEW Geochemical Data: –Data limitations; Lack of concrete geochemical data characterizing pore water from active layer; and, Presence and extent of potential impacts resulting from pore water are unknown at this time.
TECHNICAL REVIEW Reclamation Options: Consistent with industry accepted practices; Cover option will limit but not entirely prevent ingress of oxygen into underlying tailings; Proposed cover option will not prevent thaw penetration into tailings; Cover thickness of 1.75 m results in an active layer between 0.5 m to 1.5 m thick;
TECHNICAL REVIEW Reclamation Options cont’d: Geochemical impacts of seasonal freeze-thaw cycles on tailings material are not well known; Cover thickness of 1.0 m would result in an active layer of approx. 2.0 m thick; Thinner cover thickness, potential viable alternative to existing reclamation plan using 1.75 m of cover; and, Total encapsulation of tailings with permafrost is possible but not technically feasible.
TECHNICAL REVIEW Conclusions: –Excellent database; –Reclaimed tailings are frozen the majority of the year; –An esker material cover assists in limiting oxygen availability to the tailings; –Cover concept assists with maintaining tailings in a frozen condition;
TECHNICAL REVIEW Conclusions cont’d: –Current reclamation option is insufficient to fully encapsulate tailings within permafrost; –Total encapsulation of tailings in permafrost may not be technically feasible; –Covers of 1.0 m thickness or less may be a viable reclamation option; –Datagaps need to be addressed before a final reclamation option and plan can be selected.
TECHNICAL REVIEW Next Steps: –Geochemical Field Study; Active and inactive tailings deposition cells; Concentrate on active layer characterization; Comparison of data collected with existing data (column tests); and, Recalculate water balance of tailings containment area to assist in mass balance calculations.
TECHNICAL REVIEW Next Steps: –Analyses Required; Pore water chemistry; Time Domain Reflectometry (TDR) tests; Whole rock chemistry; Acid Base Accounting (ABA) analyses; Leachability tests; Water analyses; and, Chemistry of water samples from ponded water and discharge stream.
TECHNICAL REVIEW Next Steps: –Geotechnical Study; Confirmation modeling of active zone thickness with various cover options.
TECHNICAL REVIEW –TO ENSURE THE INTEGRITY OF THE NATURAL ENVIRONMENT AFTER MINE CLOSURE