- TAILINGS AND WATER MANAGEMENT FOR A COLD REGIONS MINE - Dr. Michael Davies, P.Eng., P.Geo. and Mr. Mathieu Veillette, P.Eng., P.E.

Transcription

1 - - Dr. Michael Davies, P.Eng., P.Geo. and Mr. Mathieu Veillette, P.Eng., P.E. AMEC Earth & Environmental Vancouver, British Columbia, Canada

2 Pogo Gold Mine: Teck Cominco is the operator and the mine is owed by Teck Cominco, Sumitomo Metal Mining Co. Ltd. and Sumitomo Corporation of Japan Underground mine (cut and fill and drift and fill) - annual gold production 350,000 to 450,000 ounces over at least 10 years The mill utilizes conventional milling - gravity and carbon-in-pulp technology Infrastructure - permanent camp for 200 people, gold processing facilities, water treatment plant, paste backfill plant/dry-stack tailings facility, RTP dam, off-river passive treatment works, and access road This presentation will describes the tailings and water management aspects of this northern mine

3 POGO MINE LOCATION Annual temperature range -40º C to +28ºC Site ~150 km south of the zone of continuous permafrost

4 Overall Pogo Mine View Goodpaster River ORTW Mill Site Camp Site Tailings Diversion Ditch

5 Key Issues: Development adjacent to major salmon producing river/system DOE, USEPA (NPDES), U.S. Corps of Engineers,. Zero discharge requirement (net of mine water inflows) Cold/Arid region <20 annual precipitation and negative annual average temperature Non-glaciated terrain in zone of discontinuous permafrost Conventional slurried tailings facility a non-starter Underground paste tailings backfill Surface filtered tailings dry stack

6 Plan Features Process to have flotation and leach tailings streams (~20% leach, ~80% flotation) All leach tailings U/G cemented paste backfill (approximately 50% overall tailings) Surface dry stack = only flotation tailings Freshet a large component of water balance Water management plan needed to maximize the use of recycled water Obtain sufficient runoff to operate mine Stay within zero discharge criteria Avoid water treatment costs for discharge

7 Off-River Treatment Works Mill Site Recycled Water Camp Site Diversion Ditch (Non-Contact Water) Runoff Runoff Goodpaster River Treated Water Storm water Pond Liese Creek Site Runoff Return Water Treatment plant (1525 portal) RTP Excess Water To Be Treated Runoff Runoff Diversion Ditch (Non-Contact Water)

8 Diversion Ditch Lining of Fractured Bedrock Sept 2004 Oct 2005

9 THICKENED AND PASTE STACKING Continuum

10 Dec July 2005 Mine Waste Rock FTD Toe Berm Aug Starter Berm

11 Pogo Pressure Filtered to w opt (17%)

12 FTD General Placement Shell Tailings Nearly Two Years into Service (June 2007)

13 Excavation & Stripping (Dec. 2004)

14 Sand Bedding Filter Placement (Aug. 2005) Reservoir Size: Monte Carlo Hydrology Model Rockfill Dam 40 Mgal

15 Stage Grouting Program (Aug. 2005)

16 Pressure Grouting and Tie-In Trench (Sept. 2005)

17 Complex Cover System 60-mil Textured LLDPE over GCL (Sept. 2005)

18 Tie-In Prior to Final Grout Cap (Sept. 2005)

19 Liner System at ~90% Complete (Sept. 2005)

20 Placing Cover Layer (Oct. 2005) Spillway

21 Downstream Face (Nov. 2005) Diversion Ditch DD Outfall and Spillway Channel

22 RTP First Filling Reservoir at 2044 ft ~5.4 Mgal (Nov. 2005)

23 Nearly Two Years into Service (June 2007)

24 Nearly Two Years into Service (June 2007)

25 Pogo Mine: The cold and arid nature of the project were challenges The proposed mine posed some unique geotechnical and water management issues in an extremely sensitive environmental setting Creating a permittable mine took innovation and a mine face to discharge approach Use of dewatered tailings (paste backfill and surface dry stack) were key to overall mine waste management strategy The mine is soon entering its third year of operations to date, environmental objectives are being achieved

26 - - Questions?