Management of Mining- Impacted Groundwater, Bingham Canyon Mine, Utah, USA

Transcription

1 Management of Mining- Impacted Groundwater, Bingham Canyon Mine, Utah, USA Kelly Payne Principal Advisor, Closure & Remediation Kennecott Utah Copper LLC

2 This Morning s Discussion Nature of Problem Regulatory Framework Containment and Remediation Water Treatment Acidic Water Neutral Water Cleanup Timeframe

3 Acknowledgements Technology & Innovation

4 Site Location 5 October 2009 Remediation of ARD-Contaminated Groundwater 4

5 Nature of Problem

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12 Source Controls

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16 Regulatory Framework

17 Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) 1986 EPA begins Preliminary Site Investigation 1994 Site proposed for NPL listing 1995 MOU between EPA, State of Utah, and KUC 1998 RI/FS completed 2000 ROD issued 2002 RDRA completed 2008 Consent Decree entered 2008 NPL proposal withdrawn

18 Natural Resource Damage 1986 State of Utah files Natural Resources Damage (NRD) claim 1992 Initial settlement rejected, Jordan Valley Water Conservancy District (JVCWD) intervenes 1995 NRD settlement approved, KUC provides $37M to restore, replace, or acquire equivalent 2004 State approves a joint Kennecott/JVWCD project

19 Remedies EPA through CERCLA authority for Zone A: Maintain source controls Contain the plume through pumping Remediate the aquifer through pumping and monitored natural attenuation Treat extracted groundwater and dispose of treatment residuals UDEQ through Natural Resources Damage claim settlement: KUCC to construct and operate a RO treatment plant KUCC to fund construction of a second RO plant to be owned and operated by local water district Each plant to produce 3,500 ac-ft per year for 40 years

20 Containment and Remediation

21 Acidic Groundwater Well Sulfate Groundwater Well

22 Acidic Groundwater Wells ECG1146 BSG1201 BSG2784 Installed Material Stainless Steel Stainless Steel Stainless Steel Diameter 18-inch 18-inch 18-inch Total Depth 760 ft bgs 752 ft bgs 870 ft bgs Screen Intervals ft bgs ft bgs ft bgs ft bgs Static Water Level 380 ft bgs 450 ft bgs 410ft bgs Pumping System 250 HP SS 200 HP SS 200 HP SS Submersible Submersible Submersible Average Pumping Rate 850 gpm 600 gpm 600 gpm

23 Sulfate Groundwater Wells BFG1200 B2G1193 LTG1147 Installed Material Stainless Steel Stainless Steel Carbon/Stainless Diameter 18-inch 18-inch 16-inch Total Depth 820 ft bgs 1070 ft bgs 605 ft bgs Screen Intervals ft bgs ft bgs ft bgs Static Water Level 420 ft bgs 450 ft bgs 420 ft bgs Pumping System 350 HP SS 350 HP SS 200 HP SS Sumbersible Sumbersible Sumbersible 350 HP Booster 350 HP Booster 250 HP Booster Average Pumping Rate 1400 gpm 1400 gpm 600 gpm

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25 Acidic Water Extraction 3000 Acre-Feet per Year BSG BSG ECG Total ,580

26 ECG1124A ECG1124B ECG1124C ECG1146 DTW ECG1124B Sulfate (mg/l) A E B C Screened Intervals and Depth to Water (feet below ground surface)

27 Water Treatment

28 Zone A Pump and Treat Strategy BARRIER WELLS (~3,300 gpm) REVERSE OSMOSIS TREATMENT PLANT DRINKING WATER (2,400 GPM) CONCENTRATE JORDAN VALLEY WATER CONSERVANCY RECYCLE / DISCHARGE ACID WELLS (~2,300 gpm) TAILINGS LINE AQUEOUS SOLIDS RECYCLE / DISCHARGE TAILINGS IMPOUNDMENT Post mine closure HIGH-DENSITY SLUDGE LIME TREATMENT PLANT AQUEOUS SOLIDS DISCHARGE REPOSITORY

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30 Reverse Osmosis Treatment Plant Configuration Feed Rate Two 2-stage skids 3000 gpm to membranes 200 gpm to remineralization 3200 gpm total Membranes Hydranautics ESPA2 (sprial wound polyamide) Pressure Vessels Protec and CodeLine Recovery Rate 71 to 74% Production 2200 gpm permeate 2400 gpm product

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33 Zone A Treatment Plant Water Delivery 4,000 Acre-Feet per Year 3,000 2,000 1,000 0 YE 5/31/07 YE 5/31/08 YE 5/31/09 Annual 3,843 3,299 3,536 Rolling Avg 3,843 3,571 3,559

34 Picture of RO Scaling

35 Picture of dumps/reservoir

36 Picture NP5

37 Aerial of Tailings System

38 Picture of NSB

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40 Management Criteria The neutralization potential (NP) value of samples collected from the tailings North Splitter Box should be either greater than or equal to the NP of Copperton Mill Tailings for the month or at least 5 t CaCO3 eq/kt, using a six-month rolling average. Aqueous alkalinity should be greater than or equal to 10 mg CaCO3 eq/l at least 90% of the time. Aqueous alkalinity will be evaluated as a rolling six-month average. The aqueous ph at the North Splitter Box should be greater than or equal to 6.7 during at least 90% of the time over a calendar year.

41 Tailings Neutralization Potential (t CaCO3/kt) Monthly 6-Month Average Date GMT NSB GMT NSB Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

42 Tailings Aqueous Alkalinity (mg CaCO3/l) Monthly 6-Month Average Date GMT NSB GMT NSB Jan Feb Mar Apr May Jun Jul < Aug Sep Oct Nov Dec

43 Tons Per Hour or Gallons Per Minute Concentrator Throughput (TPH) Acidic Water Pumping (GPM) Tailings ph at North Splitter Box ph 0 6 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan

44 Picture of Scaling

45 Cleanup Timeframe

46 Column Leaching Study

47 Geochemical Models Extrapolation based on interpretation of earlier column data Extrapolation using data from individual wells that have undergone complete recovery Expanded 1D geochemical model Empirical rinse curve model Extended 1D advection-dispersion model with mass extraction Acidity comprised mostly of mineral acidity in the form of elevated Al and Fe concentrations Concentration of acidity estimated for water extracted from the two extraction wells, ECG1146 and BSG1201

48 Calculated lime demand 6 Lime demand (t/ml) Rinse curve model Extrapolated well data model Advection-dispersion-extraction model Geochemical model (clean) Geochemical model (transition) Upper 95% confidence limit of all models Year