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CHEM 301 TRU (30Mar2007) .pdf


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Post-Closure Activities at the
Nickel Plate Mine: A Case-Study in
Aqueous Environmental Chemistry
Sierra Rayne
Department of Chemistry
Thompson Rivers University

1

Post-Closure Activities at the Nickel Plate Mine:
Site History




Located ~300 km east of Vancouver
One of BC’s oldest mine sites
Multiple owners






underground workings from ~1890s-1950s
open pit operation from 1980s-late mid-1990s
current owner is Barrick Gold

Site produced 2.5 million ounces of gold and
600,000 ounces of silver

2

Post-Closure Activities at the Nickel Plate Mine:
Geology of the Area



… in the 400 km2 Hedley Gold Basin …
… hosted by late Triassic Nicola Group rocks  most economically productive rocks in BC




gold ore bodies at Nickel Plate are strata-bound diorite intrusions and skarn alteration




from Hedley to Princeton to Kamloops for over 200 km
Reduced calcic type with high sulphide content and high pyrrhotite:pyrite ratios

Major minerals present:












native gold: Au
native bismuth and copper: Bi and Cu
also elevated levels of the
pyrite: FeS2
lanthanides/actinides
pyrrhotite: Fe(1-x)S (x = 0 to 0.2)
chalcopyrite: CuFeS2
arsenopyrite: FeAsS
tellurides [e.g., hedleyite (Bi7Te3), tetradymite (Bi2Te2S)]
cobaltite: (Co,Fe)AsS
maldonite: Au2Bi
tetrahedrite and pyrargyrite: Cu12Sb4S13 and Ag3SbS3
gersdorffite and breithauptite: NiAsS and NiSb
3

Post-Closure Activities at the Nickel Plate Mine:
Summary of Major Environmental Issues
1. NORTH PIT
- sulfide-bearing minerals (pyrite/arsenopyrite) in walls (>500 m deep)
- likely to generate net acid-rock drainage (ARD) within years to decades
- some regions already have ARD  high sulfate loadings
- complex hydrogeology  fault line through center of pit
- old underground workings intersect the pit … can walk down to Hedley
- drains west to Hedley Creek

2.
1.

3.

2. NORTH WASTE DUMP
- high nitrate loadings from blasting residues
- high sulfate loadings
- likely to generate ARD over time
- elevated As, Co, Zn, Se, …
- lanthanide/actinide rich geochemistry

3. CANTY WASTE DUMP/PIT LAKE COMPLEX
- high nitrate loadings from blasting residues
- poorly understood limnology of pit lake
- complex hydrogeology  old U/G workings intersect pit lake
- difficulty in re-establishing vegetation on waste dump
4. SOUTH WASTE DUMP
- high sulfate/nitrate loadings
- some elevated metals
- will likely go acidic  nightmarish location for drainage collection

6.

4.

5.

5. UNLINED TAILINGS FACILITY
- high As, Co, …, and other toxic metals
- high cyanide/cyanate levels in porewaters
- it leaks down the highside and into nearby streams
6 WATER TREATMENT PLANT
- collects seepage from tailings facility perimeter collection system
- mainly for removing cyanide/cyanates and metals
- outdated facility  high operating costs / inability to adapt
4

Post-Closure Activities at the Nickel Plate Mine:
1. The North Pit
REAL ISSUE:
ARD from pit walls and U/G workings
4FeS2 + 15O2 + 2H2O  2Fe2(SO4)3 + 2H2SO4
RESEARCH  materials science for pit sealing, geochemical kinetics

Drainage complexities!

Old U/G workings
(i.e., walk from pit to Hedley)
Fault line through pit

5

Post-Closure Activities at the Nickel Plate Mine:
2. North Waste Dump





Major source of sulfate and nitrate loadings to
local creeks
Also high in As and Se
Likely going acidic over next 5-10 years
Most drainage heads east into Cahill Creek
– but some likely heads west through North Pit and
into Hedley Creek

RESEARCH QUESTIONS:
- need accurate models of hydrology / hydrogeology of dump
linked to geochemical weathering rates
- better understand lanthanide mineralogies and their response
to ARD, speciation, toxicity, possible treatment methods

6

Post-Closure Activities at the Nickel Plate Mine:
3. Canty Waste Dump/Pit Lake Complex
Drainage heads south into Cahill Creek …
CANTY WASTE DUMP RESEARCH ISSUE:
- revegetation  phytotoxicity of As and Se rich soils? along
with poor nutrient status…

CANTY PIT LAKE RESEARCH ISSUES:
- pit lake the big unknown at Canty complex
- couple hundred meters deep
- water quality at surface is ‘ok’ (high sulfate, nitrate, As)
- nothing known about limnology, WQ at depth, drainage
paths, risk from ‘turnover’, etc…

7

Post-Closure Activities at the Nickel Plate Mine:
4. South Waste Dump





Sulfate concentrations in drainage increasing
over time (sulfide oxidation ‘heating up’? 
autocatalysis?)
Still high nitrate blasting residues
Long-term collection and treatment the issue:


Peripheral passive treatment walls?

1.
2.
3.
4.
5.
6.

On top of mountain
Will have ARD
Complex flow paths
130 km U/G beneath
Buried pit lakes
Buried tailings?
8

Post-Closure Activities at the Nickel Plate Mine:
5. Tailings Facility • THE MAJOR CURRENT PROBLEM ON-SITE:
– 50-odd million tons of cyanide/arsenic/sulfate/etc. rich
clayey-siltey material hanging off the side of a mtn!
– unlined facility  it leaks!
– perimeter well collection system, but it misses a lot…

Also receives drainage
from South Waste Dump

RESEARCH ISSUES:
- use of compacted biosolids as an impermeable cap
also applies to waste dumps on-site
- 3-D coupled hydrologic/hydrogeologic/geochemical models
- reactive permeable barriers for passive treatment?
- subsurface imaging and modelling to see how far the plume
has migrated downhill…

9


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