HARDY AND KIDD ACID DRAINAGE AND METAL LEACHING HISTORIES: CONTRASTS AND COMPARISONS

Transcription

1 HARDY AND KIDD ACID DRAINAGE AND METAL LEACHING HISTORIES: CONTRASTS AND COMPARISONS Ronald V. Nicholson,Ph.D. Stantec Consulting Ltd. 1 th Annual BC ML/ARD Workshop Vancouver, December 2-3, 23

2 THE ARD / Metal Leaching MODEL Acid + Metals Time

3 THE ARD / Metal Leaching MODEL Scale ($$$$) Time (Scale $$$$)

4 Kidd Tailings and the Hardy Mine Site Kidd Tailings Active Zinc, Copper High Sulphide Treatment ongoing Hardy Mine Site Inactive Since 1972 Nickel, copper High Sulphide No Treatment

5 Kidd Tailings (South Section) 1,2 hectares Thickened Tailings Discharge #2 Lime Station Drainage North Cell South Cell Pond A Water Treatment #1 Lime Station

6 Older Oxidized Tailings in Foreground Freshly Deposited Tailings in Background

7 Spatial Trends of Dissolved Sulphate, Iron and Zinc in Pore Water (top 5 cm) T1E T1A T1I T1 Q #2 Lime Station North Cell T1 L Maximum Concentrations in extracted water (mg L -1 ) Sulphate Iron Zinc South Cell Pond A T1Q T1L T1I T1E T1A #1 Lime Station

8 Tailings Deposition #2 Lime Station North Cell South Cell Pond A #1 Lime Station

9 Tailings Deposition #2 Lime Station North Cell South Cell Pond A #1 Lime Station

10 Tailings Deposition #2 Lime Station North Cell South Cell Pond A #1 Lime Station

11 Tailings Deposition #2 Lime Station North Cell South Cell Pond A #1 Lime Station

12 Tailings Deposition #2 Lime Station North Cell South Cell Pond A #1 Lime Station

13 Tailings Deposition #2 Lime Station North Cell South Cell Pond A #1 Lime Station

14 Oct. Dec.97 Nov. Aug. Sept. July. Feb. Mar. Apr. May. June. Lime Usage Dec.96 Jan. Monthly Requirement Cumulative Amount Date Lime Usage (tonnes)

15 Calculated Lime Demand at Treatment Plant (Assuming No Mitigative Action on Tailings) Lime Demand (kg Lime d -1 ) 35, 3, 25, 2, 15, 1, 5, On the Rise Time (Years)

16 Hardy Mine Site Tailings Pond Waste Rock (Removed) Beach Open Pit Pyrrhotite Deposits Onaping River

17 Groundwater Flow Surface Flow

18 Sep-2 Sep-2 Sep-2 Jul-98 Mar-99 Dec-99 Aug- Apr-1 Dec-1 Jul-96 Mar-97 Nov-97 Dec-1 Nov-97 Jul-98 Mar-99 Dec-99 Aug- Apr-1 Nov-97 Dec-1 Jul-98 Mar-99 Dec-99 Aug- Apr-1 Oct-95 Jul-96 Mar-97 Groudwater Below the Large Pyrrhotite Stockpile Feb-95 Oct-95 8, 6, 4, 2, SO4 Fe Oct-95 Jul-96 Mar-97 Feb Ni Cu ph Sulphate Nickel Feb-95 Ni, Cu (mg/l) SO4, Fe (mg/l) ph

19 Dec-1 Sep-2 Dec-1 Sep-2 Dec-1 Sep-2 Jul-96 Mar-97 Nov-97 Jul-98 Mar-99 Dec-99 Aug- Apr-1 Oct-95 Jul-96 Mar-97 Nov-97 Jul-98 Mar-99 Dec-99 Aug- Apr Feb-95 Oct-95 8, 6, 4, 2, SO4 Fe Oct-95 Jul-96 Mar-97 Nov-97 Jul-98 Mar-99 Dec-99 Aug- Apr-1 Feb ph Sulphate Ni Cu Nickel Feb-95 Ni, Cu (mg/l) SO4, Fe (mg/l) ph Groudwater Below the Small Pyrrhotite Stockpile

20 Apr-1 Dec-1 Sep-2 Aug- Apr-1 Dec-1 Sep-2 Oct-95 Jul-96 Mar-97 Nov-97 Jul-98 Mar-99 Dec-99 Aug- Oct-95 Jul-96 Mar-97 Nov-97 Jul-98 Mar-99 Dec-99 Feb-95 Feb-95 Groundwater below the Former Waste Rock Stockpile Down Gradient of the Open Pit Jun SO4 Fe Aug- Apr-1 Dec-1 Sep-2 Oct-95 Jul-96 Mar-97 Nov-97 Jul-98 Mar-99 Dec-99 Jun ph Sulphate Nickel Ni Cu Jun-94 Feb-95 Ni, Cu (mg/l) SO4, Fe (mg/l) ph

21 Jun-94 Oct-95 Mar-97 Jul-98 Dec-99 Apr-1 Sep-2 Jun-94 Oct-95 Mar-97 Jul-98 Dec-99 Apr-1 Sep-2 Jun-94 Oct-95 Mar-97 Jul-98 Dec-99 Apr-1 Sep ph SO4 Fe Sulphate Ni Cu Nickel Ni, Cu (mg/l) SO4, Fe (mg/l) ph Groundwater below the Former Waste Rock Stockpile Down Gradient of the Tailings Beach

22 Estimated Loadings from ALL Sources Constituent Maximum Estimated Load From Hardy (kg/day) Measured Load in Onaping River (kg/day) Sulphate 1,1 26, Nickel

23 Concluding Remarks Kidd Increased loadings during operation unexpected Unique challenges being managed by selective tailings placement and progressive reclamation Closure plan includes cover to reduce exposure and loadings Conditions expected to alter dramatically after closure but mat require indefinite treatment Hardy Loadings generally diminishing after 3 years Limited reclamation required Groundwater pathways have provided natural mitigation Complex mine site with surprisingly small impacts